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0000-0001-6123-8037
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University of Adelaide Roseworthy Campus
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University of Adelaide Waite Campus
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Diagnostic Applications | Biochemistry and Cell Biology | Cellular Immunology | Cell Development (Incl. Cell Division And Apoptosis)
Clinical health not specific to particular organs, diseases and conditions | Biological sciences | Barley |
Publisher: Asian Australasian Association of Animal Production Societies
Date: 30-10-2007
Publisher: CSIRO Publishing
Date: 1996
DOI: 10.1071/EA9960259
Abstract: The effect of maintenance v, submaintenance diets of pregnant ewes in 1991 and 1992 on establishment of the wool follicle population in their progeny, and its effect on the progeny's wool production (quantity, quality and variation across the body of the animal) to 1.4 years of age was examined. The experimental protocol used cloned animals created by bisecting embryos at day 6 of pregnancy. Each clone was placed in a ewe, which was subsequently fed from about day 50 to 140 of pregnancy at maintenance or submaintenance. Ewes on maintenance nutrition maintained liveweight throughout pregnancy, while submaintenance ewes were 12.1 kg lighter (P .001) 10 days before lambing. In 1991, a total of 74 lambs were born, including 17 sets of surviving clones. In 1992, 102 lambs were born, including 18 sets of surviving clones. Only data for the 35 sets of genetically identical 'twin' progeny and their dams are reported. Birth weights of lambs born to ewes fed at the submaintenance rate were 0.5 kg lighter (P .01) than their 'twins' born to ewes fed at maintenance. Midside secondary:primary (Sf: Pf) ratios for mature wool follicles were less (P .01) at birth, lamb and hogget shearing (1.4, 1.5 and 2.1 units respectively) for the progeny born to ewes fed at submaintenance. Progeny from ewes on the submaintenance treatment produced less clean wool, 0.1 kg to 0.4 years of age (P .01) and 0.14 kg between 0.4 and 1.4 years of age (P = 0.10), than their maintenance counterparts. Hogget wool was 0.1 pm broader (P .05), with a 0.5% units lower coefficient of variation of fibre diameter (P .01), and a position of break closer to the staple tip (P .001) for progeny of submaintenance ewes than their maintenance counterparts. There were no significant differences in yield, staple length, staple strength and percentage of fibres greater than 30 pm in diameter. Differences in mean fibre diameter arose between 1 and 1.4 years of age, coinciding with the period that the animals were grazing high quality pasture. Effects of maternal undernutrition on mean fibre diameter and Sf: Pf follicle ratios of progeny were most pronounced on the hind leg (P .01), and not significant on the front leg. However, variations in other wool quality traits across the body of the hoggets, expressed as a percentage of the midside value, were not significantly affected by maternal undernutrition. Clearly when evaluating management strategies for the pregnant ewe, the effect on lifetime production and quality of wool of their progeny needs to be considered. Merino hoggets that produce an extra 0.14 kg clean wool that is 0.1 pm finer will compensate for some extra management and feeding of their dams during pregnancy to prevent weight loss. If these effects continue throughout the life of the animal, then it will increase the cost effectiveness of feeding to maintain maternal weight over pregnancy.
Publisher: Elsevier BV
Date: 02-1994
DOI: 10.1111/1523-1747.EP12371759
Abstract: The abomasal or intravenous infusion of sulphur-containing amino acids such as cysteine or methionine into sheep on low-quality diets increases the sulphur content of the wool by increasing the synthesis of proteins containing a cysteine content of approximately 30 mol %. To investigate the molecular and cellular basis of this nutritional effect, quantitative analyses of wool keratin mRNA and protein levels, and follicle cortical cell type, were undertaken in sheep intravenously infused with cysteine. Northern blot analyses revealed that the mRNA levels of one gene family encoding cysteine-rich keratin-associated proteins (KAP4 family) expressed in the wool follicle cortex, increased approximately 5-6 times. Furthermore, the response was rapid as the mRNA levels increased approximately 3.5 times after 1 d of the cysteine infusion and, by 1 d post-infusion, they had fallen, approaching their basal level. No changes in the mRNA levels encoding the intermediate filament or the other keratin-associated protein families of lower cysteine content were observed. Concomitantly, two-dimensional polyacrylamide gel electrophoresis analysis of wool proteins showed a striking increase in the abundance of a group of cysteine-rich keratin-associated proteins in the wool by the end of the infusion period, returning to basal levels by 3 weeks later. At the cellular level, KAP4 expression was localized to the follicle paracortical cells, and the proportion of paracortical cells and the extent of KAP4 expression paralleled the changes in the cysteine infusion status of the sheep.
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/AN15601
Abstract: The objective of the present study was to evaluate the effect of including a pellet containing feed components targeted at methane-producing microbes and methane-producing biochemical pathways, into the ration of beef cattle in southern Australia. The so-called ‘methane-reducing supplement’ (MRS) components were chosen from readily available and inexpensive sources to ensure high adoption of the practice if successful. The effect of the pellet on animal performance, diet DM digestibility and gas emissions (measured using an open-circuit gas quantification system) of beef cattle in comparison with animals fed a control diet or high-quality supplement (HQS) was evaluated. In the first trial, there were no differences in DM and digestible energy (DE) intake, but the methane emission in g/day, g/MJ of DE intake (P 0.01), and in g/kg of DM intake (P = 0.01) were lower for steers fed MRS. There was also a trend to lower carbon dioxide emission (g/MJ of DE intake) in steers fed MRS (P = 0.07). In the second trial, heifers fed the MRS produced 18.7% less carbon dioxide (P 0.01) and 15.5% less methane (P = 0.01) than heifers on the HQS supplement, when expressed in g per unit supplement intake on a bodyweight basis. There was no difference in growth rate of heifers on the HQS and MRS supplements. Combining methane-inhibiting feedstuffs derived from agro-industrial by-products into supplements for cattle in southern Australia appears to be an effective means of reducing methane output and methane intensity from grazing beef cattle.
Publisher: Oxford University Press (OUP)
Date: 10-1997
DOI: 10.1111/J.1365-2133.1997.TB03778.X
Abstract: A serum-free culture system allowed the continued growth of fibre from follicles for 8-10 days. Fibre growth was responsive to changes in the level of calcium, glucose and amino acids in the culture medium, and was stimulated by the inclusion of insulin (10 micrograms/mL) in the medium. Culture of follicles in the presence of conditioned media from dermal papilla cells or of mitomycin-treated dermal papilla cells had no effect on fibre growth. Neither thyroid hormones nor hydrocortisone altered fibre growth. The progressive decline in fibre growth during follicle culture was accompanied by morphological changes in the follicle bulb. Oxidative damage did not appear to be the cause of these changes as there was no increase in fibre growth rate or longevity when antioxidants were used. This model provides a useful system to study the direct effects of various hormonal, nutritional and growth factors of fibre growth and follicle metabolism.
Publisher: CSIRO Publishing
Date: 1985
DOI: 10.1071/AR9850451
Abstract: Variations in the wool growth rate of sheep fed diets containing cereal grains were investigated. In experiment 1, eight sheep consuming similar quantities of a pelleted diet of barley grain and lucerne chaff (60:40 by weight) were selected for high (n = 4) or low (n = 4) wool growth rate. These wool growth differences were eliminated by feeding a high-protein, predominantly roughage diet. Subsequent reintroduction of the high-grain diet regenerated wide between-sheep variance, but there was little evidence of repeatability of performance on this ration. These variations in wool growth were examined in experiment 2 in terms of rumen fermentation pattern and postruminal protein flow. Ten sheep with simple cannulae in the rumen and abomasum were given a pelleted lucerne chaff diet for 14 weeks and the high-grain diet of experiment 1 for a further 16 weeks. The variance of all measured characters was low on the lucerne diet, but the high-barley diet generated wide variance in rumen fermentation pattern, protein flow from the rumen and wool growth rate. Fermentations characterized by high ammonia level, high minimum fluid pH and high butyrate molar proportion were associated with high urinary nitrogen output, high diet digestibility and low postruminal protein flow. Wool growth rate was closely related to protein flow on the high-grain diet alone (r2 = 0.77, P 0.01) and for the high-grain and lucerne diets considered together (r2= 0.86, P 0.001).
Publisher: Oxford University Press (OUP)
Date: 08-2022
DOI: 10.1111/JAM.15558
Abstract: To compare the caecal microbiota of layer, broiler, and intermediate F1 layer × broiler cross birds with the hypothesis that significant differences in caecal microbial composition would persist between the three groups when host and environmental interactions were minimized. Caecal contents were characterized using 16S rRNA for males of broiler (n = 12), layer (n = 12) and F1 layer × broiler cross (n = 9) birds that were hatched and reared under the same conditions. The microbial community structure differed significantly between the three groups of birds at phylum, genus and OTU levels, with clear separation of the groups observed. Firmicutes was the phylum most represented across s les however, the high abundance of Proteobacteria in the layer birds at d28 post-hatch was unexpected, and driven by a higher abundance of E. coli. The microbiota phylotype between broilers, layers and their F1 cross significantly differed in community structure, ersity and relative abundance in the absence of environmental confounding, which is generally difficult to avoid in microbial studies. The results provide a unique comparison and evidence that there is a strong genetic component driving microbial composition within poultry strains, despite the embryonic development occurring in ovo.
Publisher: Elsevier BV
Date: 2021
Publisher: Cambridge University Press (CUP)
Date: 23-06-2016
DOI: 10.1017/S2040174416000283
Abstract: Intrauterine growth restriction (IUGR) has adverse effects on metabolic health and early life, whereas physical activity is protective against later development of metabolic disease. Relationships between birth weight and physical activity in humans, and effects of IUGR on voluntary activity in rodents, are mixed and few studies have measured physical activity in a free-ranging environment. We hypothesized that induced restriction of placental growth and function (PR) in sheep would decrease spontaneous ambulatory activity (SAA) in free-ranging adolescent and young adult progeny from multi-fetal pregnancies. To test this hypothesis, we used Global Positioning System watches to continuously record SAA between 1800 and 1200 h the following day, twice during a 16-day recording period, in progeny of control (CON, n =5 males, 9 females) and PR pregnancies ( n =9 males, 10 females) as adolescents (30 weeks) and as young adults (43 weeks). PR reduced size at birth overall, but not in survivors included in SAA studies. In adolescents, SAA did not differ between treatments and females were more active than males overall and during the day (each P .001). In adults, daytime SAA was greater in PR than CON females ( P =0.020), with a similar trend in males ( P =0.053) and was greater in females than males ( P =0.016). Adult SAA was negatively correlated with birth weight in females only. Contrary to our hypothesis, restricted placental function and small size at birth did not reduce progeny SAA. The mechanisms for increased daytime SAA in adult female PR and low birth weight sheep require further investigation.
Publisher: CSIRO Publishing
Date: 1994
DOI: 10.1071/AR9941137
Abstract: Two groups of sheep were formed with similar mean fibre diameter (D) but differing rate of fibre elongation (L), and two groups with similar mean L but differing D. The sheep were placed on a low plane of nutrition for 8 weeks followed by a high plane of nutrition for a further 7 weeks. L, as a result of selection and nutrition, ranged from 268 to 515 8m/day, D from 17.5 to 32.8 8m, and LID ratios from 13 1 to 24.5 between in iduals. Nutrition significantly influenced the dimensions of the follicle bulb and dermal papilla, the rate of ision of follicle bulb cells, the dimensions of the cortical cells, and the production ratio (the ratio of fibre area to fibre-plus-inner root sheath area). The high and low diameter groups differed in bulb and papilla dimensions and in the rate of bulb cell ision. The high and low fibre length growth phenotypes differed only in papilla length and cortical cell length. Stepwise multiple regression analysis revealed that a model including terms for nutrition, phenotype group and cortical cell length accounted for 0.60 of the variance in fibre L (P 0.0001). Fibre D was best accounted for by nutrition, phenotype group, cortical cell volume and papilla area ( Ra2 = 0.88, P 0.0001). This differential dependence of the fibre dimensions on follicle characters means that the shape of the fibre has the potential to change in situations where cortical cell length, cortical cell volume and papilla size are differentially altered. Several hormonal, nutritional and selection regimes known to alter L/D must have this effect, but simple nutritional changes such as the one imposed in this experiment apparently do not, as there was no change in fibre L/D. The follicular efficiency of fibre production (measured as fibre output per unit bulb tissue or per unit bulb cell produced) in sheep producing fine (20.3 8m) wool was similar to that of sheep producing coarse (27.0 8m) wool. There appears therefore to be no inherent inefficiency in small follicles producing fine wool and thus no follicular impediment to the production of large amounts of fine wool.
Publisher: Bioscientifica
Date: 11-1988
Abstract: Parous Merino ewes were maintained outdoors in feedlots during the beginning of the spontaneous breeding season and fed a maintenance ration of wheaten hay. For 14 days, ewes in each of 4 groups (N = 40/group) were given supplements of lupin grain or formaldehyde-treated casein and/or wheat starch. These were calculated to supply equivalent amounts of protein post-ruminally and/or digestible energy. Supplementation with lupin grain significantly increased ovulation rate by 37% by increasing the proportion of ewes with two ovulations. Similar increases in ovulation rate were achieved by increasing the supply of digestible protein post-ruminally in the casein and casein + starch-supplement groups. Increasing the intake of digestible energy separately in the starch-supplement group did not increase ovulation rate. It is concluded that increases in ovulation rate in ewes fed a lupin supplement are the result of significant increases in the amount of protein digested post-ruminally.
Publisher: Cambridge University Press (CUP)
Date: 10-1984
DOI: 10.1017/S0021859600047456
Abstract: The potential benefits of high-energy supplements, such as cereal grains, for grazing ruminants are commonly eroded by an accompanying depression in the digestion and intake of the basal herbage (McCullough, 1959). Low ruminal pH ( 6·0) induced by the rapid rate of production of the acids of starch fermentation, and competition between cellulolytie and amylolytic bacteria for limited nutrients, are known to be responsible for inhibition of cellulolysis (Terry, Tilley & Outen, 1969 Stewart, 1977 el Shazly, Dehority & Johnson, 1961). However, there are reports of reduced roughage digestion when nutrients appear to be non-limiting and pH is maintained above 6·0 (Gilchrist et al. 1979 Henning et al. 1980). The possibility remains that intermediates or end products of starch digestion have specific inhibitory effects on the numbers of cellulolytie organisms or on the activity of their extracellular cellulases.
Publisher: Elsevier BV
Date: 2009
Publisher: Oxford University Press (OUP)
Date: 06-06-2018
DOI: 10.1093/TAS/TXY064
Abstract: The prenatal environment has been shown to have significant effects on the lifelong health of offspring in humans and other species. Such effects have not been studied extensively in avian species but could prove important, especially in the case of severe feed restriction imposed on broiler breeder hens to prevent obesity and reduce rate of lay. Feed restriction can potentially affect not only nutrient supply to the embryo but stress hormone levels within the hen. This study investigated the impact of nutrient restriction of the breeder hen on growth rate and immune responses in the progeny with the objective to measure the impact of feed restriction of broiler breeder hens on growth and immune response of the progeny. Broiler breeder hens were feed restricted from 24 wk of age and maintained at three bodyweights 3.4, 3.6, and 4.0 kg until 43 wk of age and behavioral and physiological measures of stress recorded. Chicks were hatched from each hen treatment and at day 7 vaccinated for infectious bronchitis virus (IBV) and at 16, 18, and 20 d old given an immune challenge of lipopolysaccharide. Growth and immune responses of these birds were then recorded. Sex ratio was affected by hen bodyweight, with a significantly increased proportion of males hatched from heavy hens. Growth rate from 35 to 42 d of age was reduced in male progeny from low bodyweight hens. Female progeny from heavy hens responded to an immune challenge by reduced live weight and increased heterophil: lymphocyte ratio, suggesting a more robust immune response in these birds than in the progeny from lower bodyweight hens. Overall, progeny from heavy hens had increased antibodies at day 35 to the vaccination of IBV compared with progeny of low bodyweight hens, also suggesting an improved immune response in these birds. Breeder hens restricted to the lowest feed level showed behaviors indicative of increased stress (object pecking) and an increased heterophil: lymphocyte ratio. Feed restriction of broiler breeder hens increased indices of stress in hens and resulted in offspring that have reduced growth rate and immune response in a sex-dependent way.
Publisher: Elsevier BV
Date: 06-2012
Abstract: Clostridial infection of the intestine can result in necrotic enteritis (NE), compromising production and health of poultry. Mucins play a major role in protecting the intestinal epithelium from infection. The relative roles of different mucins in gut pathology following bacterial challenge are unclear. This study was designed to quantify the expression of mucin and mucin-related genes, using intestinal s les from an NE challenge trial where birds were fed diets with or without in-feed antimicrobials. A method for quantifying mucin gene expression was established using a suite of reference genes to normalize expression data. This method was then used to quantify the expression of 11 candidate genes involved in mucin, inflammatory cytokine, or growth factor biosynthesis (IL-18, KGF, TLR4, TFF2, TNF-α, MUC2, MUC4, MUC5ac, MUC5b, MUC13, and MUC16). The only genes that were differentially expressed in the intestine among treatment groups were MUC2, MUC13, and MUC5ac. Expression of MUC2 and MUC13 was depressed by co-challenge with Eimeria spp. and Clostridium perfringens. Antimicrobial treatment prevented an NE-induced decrease in MUC2 expression but did not affect MUC13. The expression of MUC5ac was elevated in birds challenged with Eimeria spp./C. perfringens compared with unchallenged controls and antimicrobial treatment. Changes to MUC gene expression in challenged birds is most likely a consequence of severe necrosis of the jejunal mucosa.
Publisher: CSIRO Publishing
Date: 2007
DOI: 10.1071/AR06327
Abstract: The development of the follicle population in Merino sheep skin was studied from 30 days pre-partum to 112 days post-partum in single- and twin-born Merino lambs. The total number of primary follicles estimated from primary follicle density and skin surface area did not change over this period, while secondary follicle number increased to Day 28 post-partum in singles and Day 56 post-partum in twins. Twins had 14% fewer total follicles than singletons (P 0.001), largely reflecting a bodyweight (hence estimated skin surface area) difference of 10%, with little difference in total follicle density (P 0.05). Immediately post-partum there was a 36% decrease (P 0.0001) in the secondary to primary follicle ratio (S/P) of the twin lambs, while a small non-significant decrease (7% P 0.05) occurred in the single lambs. This attrition coincided with a surge in plasma cortisol concentration that commenced ~12 days before birth and persisted for 6–12 days post-partum. The surge in plasma cortisol concentration occurred in both single and twin lambs, commencing on Day 138 of gestation however, the peak cortisol concentration and the period over which cortisol remained elevated was greater in twin lambs than in singletons (P 0.001). This study confirms a previous finding of a perinatal reduction in S/P ratio in Merino sheep. The reduction was greater in twin lambs than in singletons but the follicles of twins recovered rapidly so that there was little difference in final S/P ratio between birth types after Day 30 post-partum. The postnatal follicle reduction followed the perinatal surge in plasma cortisol concentration and appeared to reflect the magnitude of the cortisol surge in that twins, which displayed a higher peak cortisol concentration, had a greater reduction in active follicles than singletons.
Publisher: CSIRO Publishing
Date: 1990
DOI: 10.1071/AR9900741
Abstract: The birth rate of cells in the wool follicle cells (CBR) was measured in two experiments on sheep differing widely in wool growth rate as a consequence of differences in nutritional regime. In Experiment 1, CBR was determined in one sheep on a high and one on a low plane of nutrition by two methods: the colchicine-metaphase arrest method, or from the product of total cell number and cell cycle time (the latter determined by DNA labelling with 5-bromo-2'-deoxyuridine (BrdU) and analysis of the fraction of mitoses labelled curve). CBR by colchicine was 0.73 and 0.56 of that determined using BrdU for the low- and high-plane sheep respectively. Cell cycle times were 26.5 h (low nutrition) to 18.6 h (high nutrition). In Experiment 2, CBR was again measured by the colchicine method, and from the rate of increase in labelled cells following a pulse dose of BrdU, in sheep on two levels of nutrition (n = 4llevel) and with a 3.7-fold difference in wool growth rate. Again, CBR by colchicine was only 0.41 (high nutrition) to 0.74 (low nutrition) of estimates made using the BrdU method, this difference being statistically significant only for sheep on the high plane of nutrition. Nutrition significantly altered CBR determined by colchicine (Pc0.001) and by BrdU (Pc0.034). The rate of fibre growth per follicle measured on two separate occasions was closely related to CBR measured using colchicine (r= 0.83, P 0.01 and 0.8 1, P c 0.02) or BrdU (r= 0.73, P c 0.04 and 0.64, P 0.08). It is concluded that CBR is a major determinant of fibre growth, but that colchicine depresses CBR. Previous estimates of mitotic activity in wool follicle bulbs have been made using colchicine and are thus probably underestimated. The technique using BrdU labelling and the subsequent rate of increase in labelled cells appears to be a useful one for estimating follicle cell kinetics.
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/AN15373
Abstract: Increasing evidence that the maternal environment influences the programming of developing embryos and fetuses through epigenetic mechanisms has significant potential application in the broiler industry. The broiler breeder hen is subjected to restricted-feeding regimes to maximise egg quantity and quality, but the genetically high-intake potential of these birds makes this regime a stressful one. We propose that this stress is signalled to the developing embryo via changes in yolk composition as an evolutionary adaptation to changing environments, and that exposure to high levels of corticosteroids in ovo is associated with developmental reprogramming, which has effects on the behaviour, health and growth of the progeny. The present paper describes some preliminary results from a series of trials designed to elucidate the relationship between breeder hen diet and egg composition, and the growth, behaviour and immune function of the progeny. We conclude that manipulation of the breeder hen diet is an untapped opportunity to maintain the competitiveness of the chicken meat industry and further, that achieving improved productivity by this means may be compatible with improved animal welfare outcomes for the hen and her progeny.
Publisher: Springer Science and Business Media LLC
Date: 27-08-2018
DOI: 10.1007/S00253-018-9281-1
Abstract: Immune function is influenced by the ersity and stability of the intestinal microbiota. A likely trade-off of immune function for growth has been demonstrated in heavier breeds of poultry that have been genetically selected for growth and feed efficiency traits. We investigated the expression of selected innate immune genes and genes encoding products involved in intestinal barrier function to determine whether function changes could be consistently linked to the phenotypic expression of feed conversion ratio (FCR), a common measure of performance within poultry broiler flocks. In addition, we compared in idual cecal microbial composition with innate immune gene expression. S les were utilised from two replicate trials termed P1E1 and P1E2. High (n = 12) and low (n = 12) performing birds were selected based on their in idual FCR data from each replicate and combined for microbiota phylogenetic composition and immune gene expression analysis. Toll-like receptor 1 (TLR1La) and zonula occludens 1 (ZO1) were differentially expressed between high- and low-performing broilers. Several taxa were correlated with FCR of these, unclassified YS2 and ZO1 were also positively correlated with each other. Interactions between taxa and differentially expressed innate immune genes between P1E1 and P1E2 were much greater compared to relationships between high- and low-performing birds. At the level of phylum, reciprocal correlations between tight junction proteins and Toll-like receptors with Bacteroidetes and Firmicutes were evident, as were correlations at the genus level.
Publisher: Springer Science and Business Media LLC
Date: 09-2017
Publisher: Elsevier BV
Date: 06-1999
DOI: 10.1016/S0925-4773(99)00064-7
Abstract: Ornithine decarboxylase (ODC) is the key enzyme in the synthesis of polyamines, small cationic molecules believed to have a role in many cellular processes such as cell migration, proliferation and differentiation. We show that ODC expression is associated with cell proliferation and commitment in hair follicle development and hair growth. In embryonic epidermis, ODC is expressed in ectodermal cells at sites where follicles develop, and persists in cells at the leading edge of the follicle placode. ODC is abundantly expressed in proliferating bulb cells of anagen follicles, except for a pocket of cells at the base of the bulb. Entry of the follicle into catagen is accompanied by a down-regulation of ODC expression, which is not resumed until a new follicle is initiated. In vibrissae, ODC expression is more complex. ODC is expressed not only in the bulb but also in the hair shaft, presenting a striking biphasic pattern. Additionally, ODC is expressed in a group of outer root sheath cells in the vicinity of the follicle bulge, the putative site of hair follicle stem cells.
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/AN16745
Abstract: This study was conducted to evaluate the relationships between metabolisable energy (ME) intake and outputs of methane (CH4), rumen-derived carbon dioxide (rCO2), lung-derived carbon dioxide (lCO2), and total carbon dioxide output (tCO2) measured using an open-circuit gas-quantification system (GQS). Three trials were conducted to produce a wide range of energy intake and gas emissions to allow relationships between gas outputs and ME intake to be quantified. Gas emissions and ME intake were measured in eight Angus steers (455 ± 24.6 kg initial bodyweight Trials 1 and 2), and in eight pregnant Angus heifers (503 ± 22.0 kg initial bodyweight 5 months pregnant Trial 3). Animals were fed twice daily to allow ad libitum intake in Trial 1, whereas in Trials 2 and 3, feed intake was restricted and energy density was varied to provide a wide range of ME intakes. Animals were allocated to in idual pens during a 20-, 19- and 15-day experimental periods, and total faecal output was measured for the last 8, 4 and 4 days in Trials 1, 2 and 3 respectively. Gas emissions were measured for 16, 8 and 8 days after the adaptation period (4, 11 and 7 days) and each animal was allowed to visit the GQS every 2 h. Total CO2 in breath (tCO2) was separated into CO2 arising from rumen fermentation (rCO2) and CO2 in expired air from the lungs (lCO2) by manually identifying the eructations from normal breaths using the GQS gas-output trace. All CO2 outputs (lCO2, rCO2 and tCO2) were highly correlated with each other (r = 0.74–0.99 P 0.01). Measurement of CO2 output was more repeatable with fewer days of measurement than was CH4 output. Metabolisable-energy intake was closely related to all three measures of CO2 output (rCO2, r = 0.69, P 0.001 lCO2, r = 0.70, P 0.001 and tCO2, r = 0.73, P 0.001). Heat production was estimated from lCO2 output by assuming a value of 0.85 for the respiratory quotient of metabolised products. The heat production estimated at the extrapolated zero ME intake (0.52 MJ/kg0.75) was 60% higher than previous estimates of fasting heat production in cattle. However, our estimate was made under non-fasting, non-sedentary, non-thermoneutral conditions, so it may be a realistic estimate of maintenance energy requirement excluding heat increment of feeding. In conclusion, the open-circuit GQS can be used to provide estimates of the ME intake and heat production of cattle, and, as such, provides a valuable opportunity to describe the energy relations and efficiency of beef cattle in the field, with minimal interference to normal grazing patterns and behaviour.
Publisher: Cambridge University Press (CUP)
Date: 03-1994
DOI: 10.1079/BJN19940149
Abstract: The aims of this work were to quantify the requirements of Zn for wool growth in growing male Merino lambs, and to describe the histological lesions of Zn deficiency in skin and wool follicles. Four groups of male Merino lambs (n 4) weighing 22 kg were fed ad lib . for 96 d on diets that contained 4 (basal diet), 10, 17 or 27 mg Zn/kg. Sheep in a fifth group were fed on the diet containing 27 mg Zn/kg, but were pair-fed to sheep on the 4 mg Zn/kg diet. Zn was added to the basal diet as ZnSO 4 to give the respective treatment concentrations. Sheep fed on the diet containing 4 mg Zn/kg showed clinical signs of Zn deficiency and lower feed intakes and wool growth than sheep in the other groups. Their wool fibres were improperly keratinized and the wool follicles contained a higher proportion of apoptotic bodies than other groups. There was no evidence of parakeratosis and the rate of bulb-cell production was not affected. Sheep from other groups showed no clinical signs of Zn deficiency, and mean feed intakes and growth rates did not differ significantly between sheep fed on diets containing 10, 17 or 27 mg Zn/kg. However, wool growth was reduced in sheep fed on the diet containing 10 mg Zn/kg compared with those fed on diets containing 17 or 27 mg/kg. The mean concentration of Zn in the plasma at which wool growth was 90 % of maximum was 0.5 mg/l. The equivalent value for the diet was 12 mg/kg, with 95 % confidence intervals of 8 to 16 mg/kg. The results suggest that Zn deficiency reduces wool growth through a specific mechanism, perhaps involving impaired protein synthesis.
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/AN15099
Abstract: Lamb mortality represents reproductive wastage and an animal welfare concern. While lambs are thought to be at a thermogenic advantage following birth in comparison to other species, death from exposure can still be a major contributor to lamb mortality, largely because of the inclement conditions often prevailing at lambing. For this reason, thermogenesis has been studied extensively in neonatal lambs. Heat is produced in the neonatal lamb by shivering and non-shivering thermogenesis. The latter is heat generated by metabolism of brown adipose tissue (BAT) found largely in the thorax and peri-renal areas of the newborn lamb. Brown adipose tissue differs from normal adipose tissue in that it contains densely packed mitochondria, a high cytochrome c content and a vast vascular network. Heat is generated in BAT by uncoupling of the proton conductance mechanism from ATP production, resulting in heat production instead of stored energy. The ability of lambs to resist cooling differs among in iduals and this is likely to be due to both genetic and phenotypic factors. The heritability of cold resistance is moderate-to-high and polymorphic gene markers associated with energy homeostasis and cold-related mortality have been identified. Additionally, several aspects of the phenotype of the lamb have been associated with cold resistance. Most relate to properties of the coat, skin and bodyweight, the latter being particularly important, presumably through effects on surface area to volume ratios and subsequent heat loss. The ability of the neonate to achieve the transition from intra- to extra-uterine life has been termed physiological maturity and is associated with the ability to activate appropriate neuro-endocrinological and behavioural changes that are consistent with homeostasis of energy metabolism. Ways to alter physiological maturity of the lamb, such as nutrition, pharmacology and genetic selection, have been identified, and while these show promising results with regards to thermoregulation, a key limitation of their application has been the lack of a repeatable, representative model of neonatal cold stress. An estimation of the non-shivering component potential of a lamb’s ability to thermoregulate can be derived from norepinephrine challenges, but more useful models of real-world cold stress are climate chambers or controlled water bath tests. Further use of repeatable test models such as these with appropriate neuroendocrine and metabolic metrics will identify key components and markers of physiological maturity associated with lamb thermogenesis and survival.
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/AR03253
Abstract: South Australian Merino sheep were selected on the basis of high or low estimated breeding values (EBV) for wool growth rate (W), but with similar bodyweight, follicle density, and mean fibre diameter. Differences in the level of expression of keratin genes were examined in the skin of these sheep to test the hypothesis that ergence in EBV for wool growth is related to the production of wool proteins differing in sulfur (S) content. Further, it was proposed that this differential gene expression would be most pronounced when the supply of S amino acids to the animal was increased. Sheep selected for high EBV (+W) produced more wool per day than low EBV sheep (–W) (on average 32.5 v. 17.7 g/day clean wool, respectively P 0.05) but the S content of the wool did not differ between selection groups (2.77% v. 2.87% S, respectively P = 0.2). Expression of keratin genes including keratin-associated protein KAP 2 (a high S gene), KAP 4 (an ultra-high S gene), KAP 6 (a high glycine/tyrosine gene), and the intermediate filament gene K 2.10, did not differ significantly between +W and –W groups. KAP 2 and K 2.10 each accounted for approximately 5% of the variation in wool growth rate (WGR) but expression of none of the genes examined was significantly related to the S content of the fibre produced. This suggests that differential keratin gene expression was not the source of genetic ergence in WGR. Instead the latter likely reflects a combination of differential cellular rate and growth processes (e.g. rate of bulb cell production, hypertrophy of cortical cells), differences in the relative production of inner root sheath and fibre from the follicle bulb cell population, or differential nutrient uptake into the follicle.
Publisher: Cambridge University Press (CUP)
Date: 04-1987
DOI: 10.1017/S0021859600079557
Abstract: There is currently considerable interest in the use of anabolic compounds to improve the efficiency of animal growth and to produce leaner carcasses. While the majority of work has centred on beef production, the growth performance of sheep is also improved (Galbraith & Topps, 1981). However, little is known of the effects of anabolic steroid hormone administration on wool growth. The few experiments which have been conducted indicate that exogenous oestrogens depress wool output (Slen & Connell, 1958) while exogenous testosterone has consistently enhanced both greasy and clean wool yields (Slen & Connell, 1958 Osborne, 1968 Southcott & Royal, 1971). Little is known, however, of the effects of the synthetic steroids on wool growth. Coehlo, Galbraith & Topps (1981) reported a reduction in wool per unit body weight in sheep implanted with trenbolone acetate and oestradiol-17β, suggesting lowered efficiency of wool growth. Similarly Yasin & Galbraith (1981) noted that trenbolone acetate, in combination with either oestradiol-17β or zeranol, reduced wool output per unit body weight. Neither of these trials attempted to isolate the effects of trenbolone acetate alone from those of the androgenplus-oestrogen combination.
Publisher: Elsevier BV
Date: 02-2004
Publisher: Elsevier BV
Date: 11-2019
Publisher: Oxford University Press (OUP)
Date: 03-2021
DOI: 10.1093/AF/VFAB005
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/AN14957
Abstract: Ability to adapt rapidly from the uterine environment to self-thermoregulation following birth is a vital requirement for neonatal lamb survival. This investigation reports factors that could explain differences in thermoregulation among breeds that differ in lamb survival. Breeds such as the Merino and Border Leicester have previously been shown to be ergent for birthweight, cold resistance and lamb survival. Cross-bred (Poll Dorset Border Leicester (PDBL, n = 9) and Poll Dorset Merino (PDM, n = 25)) and pure-bred (Border Leicester (BL, n = 35) and Merino (M, n = 46)) lambs were recorded for the thermogenic measures rectal temperature at birth, cold resistance (time for rectal temperature to fall to 35°C while in a cooled water bath) and cold recovery (time to restore rectal temperature after cold exposure) at 1 day of age. In pure-bred lambs, 1 kg increase in weight resulted in a 0.25°C increase in rectal temperature at birth (P 0.001) and 4.2 min increase in cold resistance (P 0.001). In contrast, cross-bred lambs did not exhibit any relationship between birthweight and rectal temperature at birth, although they displayed a 3.2 min greater cold resistance for every 1 kg increase in birthweight (P 0.001). BL-derived lambs were more cold resistant than M lambs (cross-bred: PDBL, 67.1 ± 2.5 min PDM, 56.4 ± 1.6 min P 0.01 and pure-bred: BL, 58.1 ± 1.5 min M, 53.2 ± 1.3 min P 0.01). The quadratic relationship of glucose concentration over time during cold exposure differed with lamb breed. PDBL exhibited higher peak glucose concentrations than did PDM (11.0 mmol/L and 8.9 mmol/L, respectively P 0.01). BL took longer to reach peak glucose concentration (50 min) than did M (40 min) and this peak value was higher (BL, 9.4 mmol/L M, 7.7 mmol/L P 0.001). In conclusion, variations in birthweight and glucose metabolism are associated with breed differences in thermogenesis of neonatal lambs.
Publisher: Elsevier BV
Date: 10-2008
DOI: 10.1016/J.CYTOGFR.2008.08.005
Abstract: Investigations of the signalling between epithelial and mesenchymal compartments of skin during hair follicle initiation in utero and hair cycling have revealed the importance of the TGFbeta superfamily in ectodermal organogenesis and morphogenesis. In particular the activins, their receptors and binding proteins such as follistatin, have been shown to be important regulators of cell proliferation, differentiation and apoptosis in hair follicle initiation, hair cycling, normal skin homeostasis and wound healing. Transgenic mice lacking various components of the activin signalling pathways display varying ectodermal pathologies including altered pelage hair follicle initiation. This review summarises the activin signal transduction pathways and the interactions between activins and other TGFbeta signalling systems during hair follicle formation, hair growth cycling, skin function and wound healing.
Publisher: CSIRO Publishing
Date: 1994
DOI: 10.1071/AR9940757
Abstract: Laser Doppler velocimetry was used to investigate the cutaneous circulation and its relationship to wool growth in Finewool and Strongwool Merinos. Skin blood flow measured with the laser Doppler velocimeter (LDV) was highly correlated with estimates of blood flow obtained using 57Co-labelled microspheres (R2 = 0.85 P 0.01), although the absolute values estimated by the microsphere technique were significantly higher (P 0.001). Strongwool Merinos had a greater rate of blood flowing through the skin than Finewool Merinos, and this was associated with both wool production per unit area of skin (R2 = 0.27, P 0.01) and with the total volume of germinative tissue in the skin (R2 = 0.54 P 0.04). The relationship between the microvascular anatomy of the skin and blood flow was also examined in four Finewool Merinos and four Strongwool Merinos. Silicone rubber was infused into the deep circumflex iliac artery within the abdominal flank, from which an index of the area of vascular tissue per unit volume of skin was estimated. This index was not related to blood flow, wool growth or follicle density within nor between strains of Merinos. Both the usefulness and limitations of the LDV are discussed, and it was concluded that (a) blood flow has an important role in the level of wool produced both within and between strains of Merinos, and (b) laser Doppler velocimetry is a useful tool for the study of blood flow in the skin of sheep.
Publisher: Elsevier BV
Date: 11-2011
Publisher: CSIRO Publishing
Date: 1998
DOI: 10.1071/A97129
Abstract: The wool growth response to nutrition by Merino weaners (liveweight 33· 2±0·58 kg) bred for high or low staple strength (SS) and fed to produce changes in liveweight was examined. The hypothesis tested was that genetic differences in SS are associated with differences in along-fibre variation in diameter. Sheep fed to maintain liveweight produced wool at a more constant rate with smaller and less rapid changes in fibre diameter than that produced by sheep which lost and then gained liveweight (P 0·001). There were significant (P 0·05) but relatively small differences in wool growth rate and fibre diameter between the SS selection flocks, and wool from sheep selected for high SS had less (P 0 ·001) variation in diameter between in idual fibres than wool from sheep selected for low SS Minimum fibre diameter was most closely associated with SS, accounting for 66% (P 0·001) of the total variance in SS generated by selective breeding and nutrition. An increase in minimum fibre diameter of 1µm was associated with an increase in SS of about 5 N/ktex. Minimum fibre diameter and the rate of change in fibre diameter to the point of break along the staple collectively accounted for 72% (P 0·001) of the total variance in SS. Addition of a term for between-fibre variation in diameter measured at the point of break removed an additional 8% (P 0·001) of the variance in SS. We conclude that the mechanisms responsible for nutritionally induced and genetic differences in SS are not the same. Nutrition influences SS by affecting along-fibre diameter changes, whereas genetic differences in SS, at least as far as they are represented by the flocks used here, are largely attributable to between-fibre variations in diameter. The independence of nutritional and genetic effects on SS means that they should be exploited concurrently to reduce the incidence of tender wool production.
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.TVJL.2019.05.009
Abstract: Equine squamous gastric disease (ESGD) is common in horses and many factors, including stress, may play a role in lesion development. Hair cortisol concentration (HCC) provides a measure of medium to long-term stress and therefore, the relationship between HCC and ESGD was examined in this study. Hair s les were collected from 25 horses and gastroscopy was performed to determine the presence and severity of ESGD. Hair cortisol concentrations were lower in horses with ESGD (P = 0.014), and negatively correlated with lesion severity. Mares had lower HCC than geldings (P = 0.031), and a higher prevalence of ESGD, while age had no significant effect. Further studies are required to determine the relevance of the association between HCC and ESGD.
Publisher: CSIRO Publishing
Date: 1998
DOI: 10.1071/A98011
Abstract: A study was conducted to examine the relationship between fibre shedding and staple strength in Merino weaners genetically different in staple strength and fed different levels of nutrition. Fibre shedding at the point of break along the staple was estimated using 3 different techniques: (i) a subjective scoring system of wool follicle activity, based on their morphology in transverse skin sections (ii) the number of fibres with club-ends after differential staining to identify remnants of the shed-follicle bulb and (iii) changes in the number of fibres in the cross-section along in idual staples. Irrespective of the technique used, the estimated proportion of shed fibres did not differ significantly between the sheep bred for sound and tender wool, but increased significantly (P 0·05) in response to adverse nutritional conditions. Across all treatments, there was a significant (r2 = 0·63 P 0·001) correlation between the proportion of shutdown follicles and the percentage decrease in the number of fibres in the staple cross-section, although the average difference between the techniques was 11·5%. Both techniques indicated that, on average, about 30% of the total follicle population became inactive and shed their fibre under the most adverse nutritional conditions, and that this was as high as 50–60% for some in idual sheep. Neither of these techniques was closely correlated to the proportion of fibres with club-ends (r2 = 0·15 and 0·20, respectively P 0·01). The proportion of shutdown follicles and the percentage decrease in the number of fibres in the staple cross-section explained 54% and 52% of the variance in staple strength, respectively, compared with only 19% explained by the percentage of fibres with club-ends at the point of break. However, as fibre shedding failed to remove any variance in staple strength additional to that already attributed to along- and between-fibre changes in diameter, it is concluded that fibre shedding per se does not contribute significantly to nutritional-induced differences in staple strength.
Publisher: Elsevier BV
Date: 02-1996
DOI: 10.1111/1523-1747.EP12340634
Abstract: The activities of ornithine decarboxylase and S-adenosylmethionine decarboxylase, two of the enzymes involved in the synthesis of the polyamines, were found to be high in follicle-rich homogenates of sheep skin, and to be responsive to the nutrition of the animal. Systemic provision of the inhibitor of ornithine decarboxylase, alpha difluoromethylornithine, markedly altered the length, diameter, and composition of the fiber, the last being accompanied by an increase in the proportion of the fiber occupied by paracortical cells and an increase in the level of mRNA encoding a cysteine-rich family of keratin proteins. The growth of wool follicles cultured in media containing alpha-difluoromethylornithine was not inhibited, even at high concentrations. In contrast, low concentrations of methylglyoxal (bis)guanylhydrazone, the inhibitor of S-adenosylmethionine decarboxylase, completely inhibited fiber growth in culture follicles. Addition of spermidine to the media overcame this inhibition but spermine had no effect. Further evidence that spermine is not required for normal follicle function was provided by incubating follicles with the specific inhibitor of spermine synthase, n-butyl-1,3-diaminopropane. This inhibitor, even at high concentrations, had no effect on fiber growth in vitro. Spermidine partially overcame the growth depression that occurred in follicles cultured in methionine-deficient media, suggesting that part of the requirement for methionine is for spermidine synthesis in the follicle. These investigations provide strong evidence that the polyamines in general , and spermidine in particular, play a major role in hair growth.
Publisher: MDPI AG
Date: 16-11-2016
DOI: 10.3390/ANI6110075
Publisher: CSIRO Publishing
Date: 2013
DOI: 10.1071/AN12193
Abstract: The economically important characteristics of the adult fleece of Merino sheep, such as increases in clean fleece weight, fibre length, fibre diameter and crimp characteristics are determined during critical phases of fetal development of the skin and its appendages. Genetics plays a major role in the development of traits, but the maternal uterine environment could also influence development. Treatment of pregnant ewes with cortisol and its analogues has previously been shown to produce changes in wool follicle morphology. The aim of this study was to determine the effect of transient manipulation of maternal cortisol status during critical phases of wool follicle initiation and development in utero. From Days 55–65 post-conception, singleton-bearing Merino ewes were treated with metyrapone (cortisol inhibitor) or betamethasone (cortisol analogue). Lambs exposed to metyrapone in utero were born with hairier birthcoats than the control or betamethasone treatment groups (P 0.05), displayed a 10% increase in staple length and a reduction in crimp frequency for the first three shearings (P 0.05). Co-expression network analysis of microarray data revealed up-regulation of members of the transforming growth factor-β and chemokine receptor superfamilies, gene families known to influence hair and skin development. These experiments demonstrate that presumptive transient manipulation of maternal cortisol status coinciding with the initiation of fetal wool follicle development results in long-term alteration in fleece characteristics, namely fibre length and fibre crimp frequency. These results indicate it is possible to alter the lifetime wool production of Merino sheep with therapeutics targeted to gene expression during key windows of development in utero.
Publisher: Oxford University Press (OUP)
Date: 09-2007
DOI: 10.2527/JAS.2006-541
Abstract: Aspects of the uptake of the AA Cys, Leu, Ala, and Lys into wool follicles were investigated using short-term culture of thin strips of sheep skin. Following verification of the reliability of the model system, the sites of uptake of the radiolabeled AA were shown to differ and to be consistent with their different roles in fiber production. Cysteine appeared in the zone of keratinization immediately distal to the follicle bulb. Lysine was incorporated into the germinative cells of the follicle bulb and the cells of the inner root sheath. Leucine and Ala were incorporated into the follicle bulb, inner root sheath, and keratinizing fiber. The incorporation of all AA into the dermal papilla was low. The relative rates of uptake of the AA into the wool follicle were as follows: L-Cys (100), L-Leu (5.5), L-Ala (2.5), and L-Lys (0.8). Uptake of Cys was saturable and followed Michaelis-Menten kinetics, suggesting a carrier-mediated system, with little or no diffusion. The majority (70%) of Cys uptake into follicles was via a Na-independent system that was not inhibited by alpha-(methyl-amino)isobutyric acid or 2-amino-2-norbonanecarboxylic acid and therefore is not via the normal Cys transport systems A, ASC, or L. Uptake of Cys appeared to be via a low-affinity, high-capacity transport system, which may be unique to the fiber-producing follicle. The majority of Ala transport had characteristics consistent with the functioning of system A (Na-dependent, inhibited by alpha-(methylamino)isobutyric acid, and low substrate affinity). Leucine uptake was inhibited by 2-amino-2-norbonanecarboxylic acid but was Na-dependent, suggesting that a variant of system L operates in the follicle to transport Leu. Lysine uptake was consistent with the operation of the usual Lys transporter system y+. Diets designed to maximize wool growth should provide AA profiles reflecting the relative rates of uptake demonstrated in this study. Investigations of possible polymorphisms in genes encoding AA transport proteins in follicles may reveal a source of genetic differences in wool growth potential among genotypes.
Publisher: CSIRO Publishing
Date: 1989
DOI: 10.1071/AR9890925
Abstract: The intake and digestion of barley stubble and mature pasture were studied in grazing cattle given no supplement or supplements of fishmeal (800 g day-1 per rumen) or fishmeal (800 g day-1 per rumen) plus glucose (500 g day-1 per abomasum). Herbage intake was unaffected by supplements but was greater on pasture than stubble (P .001). While fishmeal increased ammonia levels above the basal level of 90 mg 1-1 , the flow of bacterial nitrogen was not increased. Bacterial efficiency (g bacterial nitrogen per kg dry matter apparently digested in the rumen) was 26 and 15 at pasture and stubble, respectively (P 0.008), and was uninfluenced by supplementation with fishmeal. Similarly, the bacterial nitrogen content and the ratio of diaminopimelic acid to total nitrogen in the bacteria was unaffected by supplementation. Total non-ammonia nitrogen flow and the flow of essential amino acids from the rumen were greater at pasture than stubble (P .003) and were increased by fishmeal supplement (P .01). Plasma glucose was significantly affected by herbage type but not by supplement (P .05). Plasma insulin was not significantly altered by either herbage or supplement. It is concluded that large quantities of postruminal energy and protein supplements can be given to grazing cattle with no detrimental effects on herbage intake and utilization. Further work should be conducted to identify the cause of an apparent inefficiency of bacterial efficiency in cattle on low-quality stubble. It did not appear to result from a deficiency of either ammonia or branch-chain fatty acids.
Publisher: CSIRO Publishing
Date: 1989
DOI: 10.1071/AR9890409
Abstract: Wide phenotypic variation in fibre output per follicle was generated by selecting sheep (five South Australian strongwool Merinos, one finewool Merino and one Corriedale) on this basis, and by offering these sheep a low-protein diet for 9 weeks, followed by a high-protein diet for a further 8 weeks. Clean wool production was measured over the final 3 weeks of each period, while fibre diameter, the rate of length growth of fibres and a number of follicle characters were measured over the last 7 days of each period. The rate of ision of follicle bulb cells and the total volume of the germinative region of the follicle was estimated by image-analysis of bulb sections in skin biopsy s les.With the change from the low-protein diet to the high-protein diet, the rate of clean fleece production was increased by 33% (P .002), reflecting an increase in fibre diameter (8%) and rate of length growth of fibres (26%) the volume of the germinative region of the average bulb increased 30% (P .012) and the rate of bulb cell ision by 35% (P .004) cortical cell volume also did not change (923 8m3 v. 965 8m3 the average proportion of fibre cross-sectional area occupied by paracortical cells increased from 0.2 1 to 0.35 ( P 0.01 0) the proportion of iding cells entering the fibre cortex ranged from 0.25 to 0.42 (mean, 0.31) between sheep on the low-protein diet, and from 0.22 to 0.39 (mean, 0.32) when the animals were fed the high-protein ration the effect of diet on cell distribution to fibre and inner root sheath was not significant (P .601).Phenotypic differences in fibre output were primarily related to differences in the rate of bulb cell ision (r= 0.896, P 0.001), but inclusion of a term for the proportion of bulb cells entering the fibre cortex, removed an additional, significant proportion of the variance. Cortical cell volume, on the other hand, was poorly related to fibre output.
Publisher: CSIRO Publishing
Date: 08-02-2022
DOI: 10.1071/AN21429
Abstract: Context Ruminal microbial communities are important in production ruminants, as they can affect health and production efficiency. Differences between meat- and wool-producing sheep breeds have not yet been fully explored. Aims In this study, we aimed to determine the impact of diet on ruminal microbial populations of sheep selected for different production traits, namely, meat production (White Suffolk) and wool production, and quality (Poll Merino). Methods The study utilised 24 White Suffolk and 24 Poll Merino ewes, assigned to either a roughage (20% pellet and 80% chaff) or high-grain diet (80% pellet and 20% chaff). Following acclimatisation for 21 days, they each had a ruminal s le taken and analysed for bacterial communities, using 16S rRNA sequencing. Entry and exit weight of the ewes and their feed intake were measured. Key results There was a preference for the high-grain diet (P 0.0001), with greater amounts consumed, although there was no significant difference in ewe weights between the two dietary treatments. However, White Suffolk ewes lost weight on the roughage diet, whereas all other groups gained weight (White Suffolk roughage −5.9 ± 2.6 kg, White Suffolk high-grain 7.8 ± 1.7 kg, Poll Merino roughage 9.2 ± 2.7 kg, Poll Merino high-grain 5.0 ± 1.8 kg). There were significant ruminal bacterial differences associated with both diet and breed. The average dissimilarity in ruminal bacterial phyla associated with diet was 14.13%, with the top 50% of phyla contributing to the dissimilarity being Verrucomicrobia, Lentisphaerae, Elusimicrobia, SR1 and Fibrobacteres, which were significantly more abundant in the roughage dietary group, and Proteobacteria, which were significantly more abundant in the high-grain dietary group. Conclusions We have demonstrated that although diet strongly influences the ruminal microbiota, there is a significant interaction between diet and breed in effects on ruminal microbiota and also animal performance. Implications The differences in microbial composition between breeds were related to some of the animal productivity differences of the two breeds, indicating that at least some of the genetic differences in animal productivity are generated by differences in the responsiveness of the ruminal microbiota to diet.
Publisher: Cambridge University Press (CUP)
Date: 04-2000
DOI: 10.1017/S1357729800054655
Abstract: The rôle of various classes of nutrients (energy substrates, vitamins, minerals, amino acids) in the production of wool and hair from follicles, is considered for a variety of animal species. The wool and hair follicle have evolved a number of interesting features of carbohydrate metabolism including glutaminolysis, aerobic glycolysis, significant activity of the pentose phosphate pathway, and storage and mobilisation of glycogen. Presumably the necessity to continue to produce fibre despite fluctuations in the supply of oxygen and nutrients has resulted in some of these unique features, while others reflect the high level of DNA and protein synthesis occurring in the follicle. While it is considered that energy does not normally limit fibre growth, the relative contributions of aerobic and anerobic metabolism will greatly influence the amount of ATP available for follicle activity, such that energy availability may at times alter fibre growth. Alopecia and deficient fibre growth are consistent outcomes of deficiencies of biotin, riboflavin, pyridoxine, folate and pantothenic acid, but the precise rôles of these vitamins in follicle function await elucidation. Folate, in particular appears to play an important rôle in wool production, presumably reflecting its involvement in methionine metabolism. Cholecalciferol (vitamin D) significantly alters fibre growth in cultured follicles vitamin D receptors are located in the outer root sheath, bulb, and dermal papilla of the follicle and alopecia occurs in humans with defects in the vitamin D receptor. Retinol (vitamin A), too, appears to influence follicle function by altering keratinocyte proliferation and differentiation, with direct effects on the expression of keratin genes. The receptors for the retinoids are present in the keratogenous zone, the outer root sheath, the bulb, and the sebaceous glands. Vitamin A may also act indirectly on follicle function by influencing the activity of the insulin-like and epidermal growth factors and by altering vitamin D activity. At present there is little evidence implicating alpha-tocopherol (vitamin E) or phytylmenaquinone (vitamin K) in follicular events. Of the minerals, only copper and zinc have been shown to have direct effects on follicle function, independent of effects on food intake. Copper has direct effects on the activity of an unidentified enzyme on oxidation of thiol groups to form disulphide linkages. Wool produced by copper-deficient sheep lacks crimp, is weak and lustrous. Copper is also necessary for the activity of tyrosinase and the tyrosinase-related proteins involved in melanin synthesis. Zinc, like copper, is required for the normal keratinization of fibres but again, the precise rôle has yet to be elucidated. While the importance of amino acid supply for wool growth has long been established, there are still some unaswered questions such as what are the effects of amino acids on fibre growth in animals other than sheep what are the characteristics of the amino acid transport genes and proteins operating in the wool and hair follicle and what are the specific rôles for amino acids in follicle function.
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/AN14137
Abstract: Conventional shearing of sheep is labour-intensive, expensive and presents significant occupational health and safety risks. The only alternative at present is based on injection of epidermal growth factor, which severs the fibre at the follicle level. This technology cannot be used in pregnant animals and requires application of a net to retain the severed fleece. An alternative is to create a weakened zone within the wool staple, which would be sufficiently strong to retain the fleece on the sheep while a protective covering regrows, but sufficiently weak as to allow painless and automated removal of the fleece. We demonstrate that this approach is possible using mixtures of amino acids lacking lysine and methionine. Initially we demonstrate the relationships between staple strength, a subjective ‘harvestability’ score and a subjective ‘pain’ score, using fleeces from animals treated with varying levels of cortisol to create a wide range of strengths of wool attachment. We assigned a score to the ease with which we could manually break the staples, and also to the animal’s response to breaking the staples still attached to the skin. The relationships between these variables indicated that a staple was considered harvestable and could be removed with minimal skin flinch response at a staple strength of ~10–13 N/kTex. Staples within this range were then produced by intravenous infusion of mixtures of amino acids lacking in lysine and methionine for a 5-day period. The weak point was uniformly created across the entire fleece and when a prototype roller-pin device was applied to the weakened wool, it uniformly broke the fleece of the three sheep tested. The mode of action of the amino acid treatment on wool growth was studied. There was no effect of unbalanced amino acids on the rate of follicle bulb cell ision, the number of active wool follicles, or the length of the keratinisation zone in the wool follicle. Fibre diameter was reduced by ~4 microns by treatment, and intrinsic fibre strength (strength relative to cross-sectional area of the wool fibres), was reduced by ~50%. Results of these trials are encouraging but further work is required to develop a practical, on-farm method of altering systemic amino acid supply and to design an automated, high-throughput system of severing the weakened wool.
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/AN15622
Abstract: There is considerable interest in the potential for measuring cortisol in hair as a means of quantifying stress responses in human and non-human animals. This review updates the rapid advancement in our knowledge of hair cortisol, methods for its measurement, its relationship to acute and chronic stress, and its repeatability and heritability. The advantages of measuring cortisol in hair compared with other matrices such as blood, saliva and excreta and the current theories of the mechanisms of cortisol incorporation into the fibre are described. Hair cortisol as a measure of the physiological response to stress in a variety of species is presented, including correlations with other s le matrices, the relationship between hair cortisol and psychosocial stress and the repeatability and heritability of hair cortisol concentrations. Current standards for the quantification of hair cortisol are critically reviewed in detail for the first time and gaps in technical validation of these methods highlighted. The known effects of a variety of sources of hair cortisol variation are also reviewed, including hair s ling site, sex, age and adiposity. There is currently insufficient evidence to conclude that cortisol concentration in hair accurately reflects long-term blood cortisol concentrations. Similarly, there is a lack of information surrounding the mechanisms of cortisol incorporation into the hair. This review highlights several directions for future research to more fully validate the use of hair cortisol as an indicator of chronic stress.
Publisher: CSIRO Publishing
Date: 2010
DOI: 10.1071/AN10095
Abstract: Genetic parameters (heritability, phenotypic and genetic correlations) were estimated for a range of visual and measured wool traits recorded from the 2008 shearing of the initial cohort of Merino progeny born into the Sheep CRC’s Information Nucleus Flock. The aim of this initial analysis was to determine the feasibility of selectively breeding Merino sheep for softer, whiter, more photostable wool and to quantify the likely impact on other wool production and quality traits. The estimates of heritability were high for handle and clean colour (0.86 and 0.70, respectively) and moderate for photostability (0.18), with some evidence of maternal effects for both handle and photostability. The phenotypic correlations between handle and clean colour and between handle and photostability were close to zero, indicating that achieving the ‘triple’ objective of softer, whiter, more photostable wool in the current generation through phenotypic selection alone would be difficult. There was evidence of an antagonistic relationship between handle and photostability (–0.36), such that genetic selection for softer wool will produce less photostable wool that will yellow on exposure to UV irradiation. However genetic selection for whiter wool is complementary to photostability and will result in whiter wool that is less likely to yellow. Genetic selection to improve handle, colour and photostability can be achieved with few detrimental effects on other visual and measured wool traits, particularly if they are included in an appropriate selection index.
Publisher: CSIRO Publishing
Date: 1986
DOI: 10.1071/BI9860329
Abstract: Mitotic activity in the cells of the germinative region of wool follicle bulbs was quantified by using small (0 '1-0 5 ml) intradermal doses of colchicine and selective staining of the metaphase-blocked nuclei using either crystal violet, iodine and eosin or haematoxylin and eosin. The number of metaphase nuclei present 3 h after colchicine administration increased with colchicine dose from 0 to 1 p,g and thereafter remained relatively constant up to 200 p,g colchicine. The accumulation of metaphase nuclei was linear for up to 6 h after intradermal colchicine. The metaphase-blocking effect of intradermal colchicine was confined to a radius of less than 5 cm from the injection site, allowing a number of estimates of mitotic rates to be made over a small area of skin. Such estimates revealed little variation in mitotic activity over the midside region of the sheep, although there were substantial differences in follicle activity at different sites over the body. The technique is simple, allows serial or concurrent estimates of mitotic activity to be made in the same animal, and eliminates problems associated with intravenous colchicine administration. It was used to derive the relationship between follicle activity and fibre production after nutritional changes, and to define the time course of mitotic events after administration of the antimitotic defleecing agent cyclophosphamide.
Publisher: CSIRO Publishing
Date: 1995
DOI: 10.1071/AR9950319
Abstract: Cortisol reduces wool growth at the systemic and local level, but the minimum time for a response to take place has never been reported because the methods used to measure the changes require at least 4 days of wool growth. A technique using local intradermal colchicines to estimate mitotic rate in wool follicles has been used in the present study, and can measure changes in mitotic rate over periods as short as 2 h. Within the dose range 0 to 1000 8g, intradermal injections of cortisol into adrenalectomized sheep had no effect on mitotic rate in wool follicles within 6 h. Stimulation of endogenous release of cortisol using exogenous adrenocorticotrophic hormone in entire sheep, was similarly ineffective within 5 h. Further investigations using adrenalectomized sheep revealed that bolus injections of hydrocortisone also had no effect on mitotic rate within 5 h. A fourth experiment was conducted, in which 15 adrenalectomized sheep were infused with: a control infusate for 4 days, followed by this infusate containing cortisol at a rate equivalent to 0, 0.87 or 1-82 mg kg-1 day-1 for 4 days, followed by a further 4 days of control infusate. Five hours after the change from control to the cortisol infusate, there was no significant difference in mitotic rate between treatment groups when adjusted using mean mitotic rate in the pre-cortisol period as a covariate (P = 0.887). However, 29 h of infusion with cortisol was sufficient to bring about a significant reduction in mitotic rate (P = 0.034). During the following 3 days of cortisol infusion, mitotic rate was maintained at a significantly lower level in the treated groups (P = 0.018), with the greatest effect apparent in the group which received the highest dose of cortisol. At 53 h post-cortisol infusion, there was a significant recovery in both cortisol treated groups to mitotic rates significantly above those recorded in the pre-cortisol infusion period (P = 0.003), while mitotic rate remained unchanged in the group which received no cortisol. It is concluded that acute changes in plasma cortisol concentration are not likely to produce acute changes in wool growth, but a sustained elevation of plasma cortisol concentration will reduce the rate of wool growth by reducing mitotic rate in wool follicles.
Publisher: CSIRO Publishing
Date: 1997
DOI: 10.1071/A97001
Abstract: An experiment was conducted to determine the impact of stocking rate and Merino strain on follicle morphology before and after the break of the season in the highly seasonal Mediterranean environment of southern Australia. Groups of Finewool and Strongwool Merino sheep were allocated to 9 stocking rates on mixed legume-grass pastures, and skin biopsy s les were taken at monthly intervals from February to June. A scoring system, based on the morphology of follicles in transverse section, was used to characterise these s les. The proportion of follicles classified as ‘normal’ dropped markedly, and the proportion of follicles which contained no fibre correspondingly increased, after the break of the season in April. On average about 10% of the follicles became inactive but there was considerable variability (range 2-63%) between animals. The proportion of inactive follicles was significantly affected by stocking rate but there was little difference between Merino strains. Maximum follicle inactivity coincided with the period of minimum fibre diameter and minimum liveweight in May, approximately 1 month after the break of the season. The proportion of inactive follicles accounted for 27% and 28% of the variance in staple strength of the Finewool and Strongwool strains, respectively. Minimum fibre diameter accounted for 63% and 61% of the variance in staple strength, and coecient of variation in fibre diameter accounted for 49% and 58% of the staple strength variance, respectively, in the 2 strains. Together, minimum fibre diameter and coecient of variation in fibre diameter accounted for almost 75% of the variance in staple strength in both strains. Addition of a term for the proportion of inactive follicles did not remove any additional variance in staple strength. These results suggest that the follicles of Merino sheep in Mediterranean environments undergo significant morphological changes throughout the year. These changes differ from the normal sequence of events associated with the hair cycle and appear to be associated with the break of the season in autumn. The morphological changes which occur in the follicles are similar to those induced by epidermal growth factor or cortisol, and may reflect a stress response. Our results suggest that nutritional stress is at least partially responsible for the follicular pathology described. Management strategies aimed at reducing the decrease in fibre diameter which occurs in autumn, shearing sheep in autumn to coincide with the minimum fibre diameter, and selection of sheep which have a low coecient of variation of fibre diameter, are likely to be the most effective means of preventing low staple strength in sheep grazing in Mediterranean environments. Nevertheless, the impact of follicle shutdown and changes in follicle morphology on wool characteristics other than staple strength needs to be determined.
Publisher: Elsevier BV
Date: 2008
Publisher: Informa UK Limited
Date: 08-2011
DOI: 10.1080/00071668.2011.587183
Abstract: 1. This study investigated the effect of Eimeria spp./Clostridium perfringens induced necrotic enteritis and traditional antibiotic preventatives on intestinal micro-architecture and mucin profile. 2. A total of 600 Cobb 500 broiler chickens were randomly assigned to the following three groups: (i) unchallenged, (ii) challenged, and (iii) zinc bacitracin/monensin (ZnB/monensin) (n = 25 chickens en, 8 pens/group). The challenged and ZnB/monensin chickens were in idually inoculated with Eimeria acervulina, E. maxima and E. tenella and C. perfringens type A (EHE-NE18) at 9 and 15 d post-hatch respectively, to induce necrotic enteritis. 3. The challenge procedure significantly decreased villus height, increased villus width and increased crypt depth in the challenged compared to the unchallenged chickens. Zinc bacitracin and monensin maintained villus-crypt structure similar to that of the unchallenged chickens. 4. Mucin profile was not affected by Eimeria spp./C. perfringens challenge as demonstrated by periodic acid-Schiff and high iron diamine-alcian blue pH 2 x 5 staining. Zinc bacitracin and monensin decreased the number of intestinal mucin-containing goblet cells. 5. Lectin histochemistry showed a trend towards greater Arachis hypogea (PNA) reactivity in unchallenged chickens. 6. In summary, Eimeria spp./C. perfringens challenge disrupted intestinal micro-architecture however, challenge did not appear to affect intestinal mucin profile. Traditional antibiotics, zinc bacitracin and monensin maintained micro-architecture.
Publisher: Elsevier BV
Date: 2010
Publisher: Springer Science and Business Media LLC
Date: 13-06-2013
DOI: 10.1038/IJO.2013.110
Abstract: Obesity affects more than half a billion people worldwide, but the underlying causes remain unresolved. It has been proposed that propensity to obesity may be associated with differences between in iduals in metabolic efficiency and in the energy used for homeothermy. It has also been suggested that obese-prone in iduals differ in their responsiveness to circadian rhythms. We investigated both these hypotheses by measuring the core body temperature at regular and frequent intervals over a diurnal cycle, using indigestible temperature loggers in two breeds of canines known to differ in propensity to obesity, but prior to ergence in fatness. Greyhounds (obesity-resistant) and Labradors (obesity-prone) were fed indigestible temperature loggers. Gastrointestinal temperature was recorded at 10-min intervals for the period of transit of the logger. Diet, body condition score, activity level and environment were similar for both groups. Energy digestibility was also measured. The mean core body temperature in obesity-resistant dogs (38.27 °C) was slightly higher (P<0.001) than in obesity-prone dogs (38.18 °C) and the former had a greater variation (P<0.001) in 24h circadian core temperature. There were no differences in diet digestibility. Canines differing in propensity to obesity, but prior to its onset, differed little in mean core temperature, supporting similar findings in already-obese and lean humans. Obese-prone dogs were less variable in daily core temperature fluctuations, suggestive of a degree of circadian decoupling.
Publisher: CSIRO Publishing
Date: 1994
DOI: 10.1071/AR9941159
Abstract: Literature evidence on the effects of catecholamines on wool growth is scant and the short-term effects have not been investigated. Since catecholamines are relatively short-lived, three approaches were adopted to investigate their effects on cellular events in the wool follicle over periods as short as 4 h. In vitro culture of skin revealed a reduction of DNA synthesis in response to either adrenaline or noradrenaline added to the media (P 0.001) in a dose-dependent manner (P 0.001). Intradermal injections of adrenaline and noradrenaline significantly lowered the rate of cell ision in wool follicles in comparison with control sites in vivo (P 0.05). These results indicate that the catecholamines can rapidly lower the rate of proliferative events in the wool follicle. The left superior cervical ganglion was removed from 18 sheep. The animals were exposed to a cold environment and ear temperature was monitored to indicate the likely release of noradrenaline in the skin of the cheeks or adrenaline from the adrenals. With respect to the sympathectomized side, a reduction in ear temperature on the unoperated side was associated with lowered mitotic rate at the unoperated cheek site (P 0.026). However, when the temperature of the unoperated side was not lowered, mitotic rate was not consistently lower on one side with respect to the other. Physiological levels of noradrenaline therefore mimicked the effects observed during the pharmacological studies, and the catecholamines may therefore play an important role in the regulation of wool growth.
Publisher: Elsevier BV
Date: 2019
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/EA08203
Abstract: This paper investigates the contribution of single fibre stress-strain properties to variations in staple strength induced by both selective breeding for staple strength and nutritional manipulation. Merino weaners (n = 40), selected from ‘sound’ and ‘tender’ lines of staple strength selection flocks, were allocated to feeding regimes designed to induce liveweight changes simulating typical Mediterranean seasonal changes. Average staple strength differed by 5 N/ktex between ‘sound’ and ‘tender’ selection flocks and 18 N/ktex between extreme nutritional treatments. The force-extension properties of in idual wool fibres (n = 100 per sheep) were measured using a single fibre strength meter. After normalising for differences in fibre cross-sectional area at the point of break, the key parameters used to describe the stress-strain curve for each fibre were: Young’s modulus (GPa), yield stress (MPa), stress at 15% strain (MPa), stress at break (MPa), strain at break (%) and work to break (MPa). The average stress-strain properties of single fibres differed widely between in idual sheep. Stress at break ranged from 163 to 235 MPa (44% range), strain at break ranged from 21 to 44% (103% range) and work to break from 43 to 71 MPa (65% range). There were no significant differences in any of the single fibre properties between the staple strength selection flocks, nor was there any significant interaction (P 0.05) between staple strength selection flock and nutritional regimes. Nutritional regime had a significant effect on stress at break, strain at break and work to break, but none of the single fibre stress-strain properties removed any appreciable variance in staple strength over and above that accounted for by differences in along- and between-fibre diameter variation. There appears to be little scope for improvement of single fibre stress-strain properties as a means of increasing staple strength in normal production environments. Selection directly for staple strength or indirectly using the fibre diameter variability traits is an effective method to improve staple strength.
Publisher: Elsevier BV
Date: 07-2017
DOI: 10.1016/J.BEPROC.2017.03.018
Abstract: Our understanding of the frequency and duration of maternal care behaviours in the domestic dog during the first two postnatal weeks is limited, largely due to the inconsistencies in the s ling methodologies that have been employed. In order to develop a more concise picture of maternal care behaviour during this period, and to help establish the s ling method that represents these behaviours best, we compared a variety of time s ling methods Six litters were continuously observed for a total of 96h over postnatal days 3, 6, 9 and 12 (24h per day). Frequent (dam presence, nursing duration, contact duration) and infrequent maternal behaviours (anogenital licking duration and frequency) were coded using five different time s ling methods that included: 12-h night (1800-0600h), 12-h day (0600-1800h), one hour period during the night (1800-0600h), one hour period during the day (0600-1800h) and a one hour period anytime. Each of the one hour time s ling method consisted of four randomly chosen 15-min periods. Two random sets of four 15-min period were also analysed to ensure reliability. We then determined which of the time s ling methods averaged over the three 24-h periods best represented the frequency and duration of behaviours. As might be expected, frequently occurring behaviours were adequately represented by short (oneh) s ling periods, however this was not the case with the infrequent behaviour. Thus, we argue that the time s ling methodology employed must match the behaviour of interest. This caution applies to maternal behaviour in altricial species, such as canids, as well as all systematic behavioural observations utilising time s ling methodology.
Publisher: Elsevier BV
Date: 03-2001
Publisher: CSIRO Publishing
Date: 1985
DOI: 10.1071/AR9850709
Abstract: L-Cysteine ethyl ester hydrochloride (CEE) was evaluated as a dietary sulfur amino acid supplement for increasing wool growth rate. In Experiment 1, eight sheep were offered 800 g chopped lucerne hay daily and wool growth was measured over a three-week control period. These sheep were then given a continuous infusion of either CEE per rumen, CEE per abomasum, cysteine per abomasum or continued on the basal diet alone, for three weeks, and wool growth was measured again. All supplements were equivalent to 25 mmol/day. Wool growth rate on tattooed patches in sheep given CEE per rumen or abomasum increased 67% and 75% respectively above the rates prior to infusion, while that of animals given cysteine increased 45%. Wool growth rate in the control sheep increased by only 15% in the same period. In Experiment 2, wool growth was measured in 24 sheep offered 800 g/day lucerne chaff, and again when CEE, cystine, or Na2SO4, each providing 21 mmol S/day, were combined with mineral mix and offered with the feed. CEE and cystine increased wool production by 1.9 g/sheep/day (P 0.01) and 1.0 g/day (P 0.05), respectively, above that measured in the control groups (nil- or Na2SO4- supplemented) which did not differ.
Publisher: Elsevier BV
Date: 11-1988
Publisher: Springer Science and Business Media LLC
Date: 02-05-2018
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/AN15195
Abstract: Several sheep-husbandry practices such as mulesing, castration, ear-tagging and tail-docking are currently performed with no, or little, anaesthesia or analgesia. The potential for using electrotherapies to provide analgesia during and after these operations is examined in this review. The most common electrotherapy is transcutaneous electrical nerve stimulation (TENS). TENS is the application of an electrical current from electrodes placed on the skin. Analysis of a large number of trials in humans and in animal models indicates that TENS provides effective relief from acute and chronic pain, including pain associated with surgery. There is strong evidence now that TENS analgesia operates at the levels of the periphery, the spinal cord and in the brain. The mechanisms involve the autonomic nervous system, the opioid pathways and neurotransmitters involved in descending inhibitory pathways from the brain. Centrally operating pathways mean the current does not have to be applied near the injured site and there is evidence of sustained pain relief lasting hours, days or even weeks post-treatment, particularly after very high-frequency, randomly variable current applications. Treatment of sheep during painful operations with such a current has the potential to provide immediate and possibly sustained pain relief. Combining such a treatment with electro-immobilisation of the animal would be advantageous for sheep-husbandry operations, but there is considerable evidence that high-intensity currents producing tetanic contractions are aversive and probably painful for sheep. Investigations of the application and efficacy of electrotherapies for painful sheep operations should be undertaken.
Publisher: Oxford University Press (OUP)
Date: 02-1999
DOI: 10.1111/J.1365-2133.1999.02652.X
Abstract: Wool follicle matrix cell cultures were initiated as explants from Tukidale (carpet wool) sheep primary follicle bulbs after removal of the outer root sheath. Successful explantation required coculture on collagen with intact dermal papillae. Cells had a typical epidermal morphology (pavements of flattened. polyhedral cells). Extracellular matrix from dermal papillae, conditioned media, separation of dermal papilla from bulb matrices by tissue culture inserts and feeder layers were unable to support matrix cell explantation. Cultures could be maintained for up to 14 passages during which time the cells became larger with an increased cytoplasmic/nuclear ratio and irregular outline. Proliferation of matrix cells was greater on laminin than with either collagen type I or type IV. Proliferation was considerably reduced under serum-free conditions. This was most apparent at low calcium (0.09 mmol/L). By Northern hybridization matrix cells were found to express keratin K18 at all stages of culture. Keratin K 1.15 expression was evident by the tenth passage. The wool-specific keratin K2.10 was not detected. The data demonstrate that successful wool matrix cell culture is achievable. Keratin gene expression occurs in these cells and varies with the stage of culture.
Publisher: Elsevier BV
Date: 06-2001
Publisher: CSIRO Publishing
Date: 1992
DOI: 10.1071/AR9920355
Abstract: The genetic differences in the structure and function of wool follicles and their association with wool and fibre production were examined in 6 finewool Merinos (Camden Park) and 6 strongwool Merinos (East Bungaree). The strongwool Merinos produced 2.4 times more wool per unit area of skin and 3.5 times the volume of fibre per follicle than the finewool Merinos, when both groups were maintained under similar environmental conditions. The finewool Merinos had a higher follicle density, but a lower average volume of germinative tissue in the follicle bulb and the skin, than the strongwool Merinos. The number and volume of cells in the bulb, bulb cell production rate, cortical cell size and the proportion of bulb cells entering the fibre tended to be greater in the strongwool Merinos than the finewool Merinos, but were not statistically different between strains due to a high between-sheep, within-strain variation. In a stepwise linear regression, wool production per unit area was best predicted by the volume of germinative tissue in the bulb, together with follicle density. It is concluded that genotype determines the volume of potential mitotically-active tissue in the skin, however the dynamic mechanism of fibre production is not controlled by a single character, but rather a combination of a number of characteristics.
Publisher: Wiley
Date: 02-1990
DOI: 10.1111/J.1751-0813.1990.TB07694.X
Abstract: The use of high-energy electrons for permanently depilating areas of sheep skin was evaluated. The most effective dose of electrons for depilation was 17.5Gy. Histological changes in skin treated at this dose were examined in one sheep over 18 months and in 5 sheep over 89 d. Effects of treatment on bodyweight gains and fleece growth were examined by comparing the productivity of a further 5 sheep treated on the breech with high-energy electrons, with that of conventionally mulesed sheep (n = 5) and untreated controls (n = 5). Electron treatment resulted in immediate death of cells in the germinative region of the wool follicle bulbs. Within 10 d of treatment the treated areas were completely depilated. Wool follicle shafts in the treated areas regressed rapidly towards the epidermis and remained quiescent for the whole trial (89 d). A sheep treated 18 months previously has remained largely depilated, although a few sparse fibres are present. Epidermal acanthosis and orthokeratosis were present at 26 d after treatment. The thickened stratum corneum then sloughed off, but the epidermis remained acanthotic for the entire trial. Sweat glands and most sebaceous glands were destroyed by the treatment and were replaced by fibrotic, avascular tissue in the dermis. In all other respects the external appearance of the electron-treated breech was similar to that of mulesed sheep. There were no apparent side-effects of treatment. Neither mulesing nor electron treatment altered weight gains or fleece growth rates.
Publisher: Elsevier BV
Date: 05-2018
Publisher: Elsevier BV
Date: 10-2000
DOI: 10.1046/J.1523-1747.2000.00122.X
Abstract: We have cloned ovine Barx2, a member of the Bar class of homeobox genes, and present the first description of Barx2 expression in wool follicle development. Barx2 is uniformly expressed in the embryonic ectoderm but is transiently downregulated during the initiation of follicle morphogenesis. Subsequently, Barx2 is expressed throughout the epithelial component of the developing follicle except for a small group of cells at the leading edge of the follicle placode. These Barx2-negative cells are destined to form the follicle bulb and are the progenitors of the inner root sheath and hair shaft. In adult follicles, Barx2 is expressed throughout the outer root sheath but not in the inner root sheath or hair shaft, or in dermal cells associated with the follicle. The pattern of Barx2 expression in follicle morphogenesis is similar to that of the cell adhesion molecule E-cadherin, a similarity that echoes Barx2 coexpression with the L1 cell adhesion molecule in other tissues during mouse embryogenesis. Barx2 is also expressed in tongue and esophagus, two other keratinizing tissues, and we speculate that Barx2 may have a general function in controlling adhesive processes in keratinizing epithelia.
Publisher: Wiley
Date: 08-1993
DOI: 10.1111/J.1751-0813.1993.TB07978.X
Abstract: A rapid technique for adrenalectomy of sheep was developed. Bilateral adrenalectomy was performed in a single stage operation by inducing ischaemia with latex rings of the type used commonly for the castration of lambs and calves. The success of the technique was demonstrated by failure of exogenous ACTH to increase circulating cortisol concentrations. Adrenal steroid replacement was used to maintain the sheep during the post-operative period (cortisol 0.25 mg.kg-1, deoxycorticosterone acetate 0.05 mg.kg-1). Adrenalectomised sheep were maintained for up to 20 days without glucocorticoid, provided a lowered dose of mineralocorticoid was administered (0.04 mg.kg-1 x day-1). Adrenalectomised sheep had significantly (P < 0.007) lower packed cell volume (23.75%) than normal sheep (31.24%), across a broad range of cortisol concentrations (0 to 734 ng/mL), indicating that plasma cortisol may not reflect true blood concentrations when drawing comparisons between adrenalectomised and normal sheep.
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/AN17014
Abstract: Animal producers are well aware that a low-birthweight animal is more likely to die in the first few days of life, and, if it survives, it is likely to perform poorly. We are now coming to appreciate that early life events can permanently change an animal’s developmental trajectory, also often referred to as developmental programming. This is an area of current interest in biomedicine, where the concept is known as the ‘developmental origins of health and disease’ (DOHaD). Current gaps in understanding include many of the underlying mechanisms, and whether and how we might intervene and restore the potential for healthy and productive development. This review introduces the biomedical perspective of developmental programming, reviews some of the evidence for long-term effects of early life exposures on welfare and productivity in animal production, with a focus on prenatal growth and maternal stress in pig production, and discusses options for intervening to improve long-term outcomes.
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/AN11033
Abstract: The use of animals that are resilient to challenging environments is becoming of increasing importance in animal production systems. Interest in breeds of sheep such as the Damara for sheep meat production is increasing in Australia. Anecdotally this breed outperforms the traditionally grazed Merino in the harsh rangeland environments encountered in the Pastoral Zone of Australia, but little evidence is available to support this claim. A trial was conducted to quantify differences in the efficiency of feed utilisation and growth performance of Damara and Merino sheep under two contrasting dietary regimes. Eighteen castrate males of each breed were offered a ‘low-quality’ diet (L) (7 MJ/kg ME 8% crude protein, as per manufacturer’s analysis) followed by a ‘high-quality’ diet (H) (11 MJ/kg dry matter and 16% crude protein, as per manufacturer’s analysis). On the L diet, Damaras had similar ad libitum feed intake as Merinos, but the digestibility of feed dry matter and energy was ~10% higher in Damaras than Merinos. Damaras also gained weight (38 g/day) on the L diet, while Merinos lost weight (28 g/day) (P 0.002). On the H diet the Damaras consumed 14% more feed (P 0.053) and grew 30% faster than Merinos (P 0.002), but there was no difference in the apparent dry matter or energy digestibility of the feed. At the conclusion of the trial the Damara carcasses were 22% heavier (28.1 versus 23.1 kg), and had higher dressing percentages (53.2 versus 41.5%) than Merinos, but the proportions of carcass components did not differ. The Damaras achieved higher total digestible energy intakes than the Merinos on both diets. On the low-quality feed this was achieved through higher feed digestibility and on the high-quality feed through greater voluntary feed intake. We speculate that this arises from variation between the breeds in rumen volume, particle flow and the site of digestion, but further studies are required to confirm this contention. The ability of Damara sheep to obtain more nutrients from widely differing feed bases makes them an attractive alternative sheep breed for sheep meat production. Furthermore, the presence of such variation between genotypes offers potential for selective breeding and development of commercial lines of sheep.
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/EA08150
Abstract: The potential for adopting a genetic solution to protect sheep from blowfly strike on the breech was investigated in a flock of sheep that contained several animals expressing a trait characterised by low wool coverage over the breech and through a wide channel from the anus to the udder or scrotum. A scoring system (1, bare to 5, woolly) was developed and used to determine the heritability of the trait and its phenotypic and genetic correlations with other traits of importance in a sheep enterprise. In comparison to animals with woolly breeches, the skin in the breech of animals with a low bareness score was characterised by a low density of follicles producing short, medullated fibres, with histological evidence of immune rejection and follicular atrophy. The bareness score of progeny was influenced by the score of their respective sires suggesting a strong genetic component. The heritability of bareness score was moderate to high (h2 = 0.45 ± 0.02, 0.53 ± 0.01 and 0.38 ± 0.02 at lamb, hogget and adult ages, respectively). The lactation status and age of ewes influenced their bareness score, resulting in a low repeatability (0.42) of the trait between ages in females. Genetic correlations between bareness score and most other economically important traits were low. The weight of belly wool and the weight of skirtings was genetically related to bareness score (rg = +0.52 and +0.48 respectively), indicating that animals with barer breeches tend genetically towards lighter belly wool weights and lower weight of skirtings at wool classing. Selection and breeding for bareness score should achieve relatively rapid progress towards fixing the trait in a flock and without adverse effects on other important traits. Caution should be exercised in extrapolating these results to other bloodlines and environments where genetic mechanisms or environmental influences may be different.
Publisher: CSIRO Publishing
Date: 1994
DOI: 10.1071/AR9941149
Abstract: The thyroid hormone status of Corriedale sheep was manipulated in order to produce a change in the rate of fibre elongation (L) with no concomitant change in the diameter (D) of the fibres, to allow the follicular factors responsible for fibre L to be determined. Thyroidectomy resulted in a 60% decrease in wool growth per unit area of skin and a 40% decrease in the rate of fibre volume output, due largely to a decline in fibre L from 412 ,8m/day to 277 8m/day ( P 0.0001) while fibre D was unchanged (23.9 8m v. 21.9 pm, P 0-05). Elevation of plasma thyroxine levels to 250% of Control values had no significant effect on fibre L and D, but patch wool growth was increased ( P 0.05). A high proportion (22.9%) of the follicles in the hypothyroid sheep was inactive in comparison to the low levels of inactivity in the control (1.2%) and hyperthyroid animals (0.1%). The rate of ision of follicle bulb cells was depressed by hypothyroidism and increased by hyperthyroidism (P 0.0001), but there was no effect of thyroid status on the size of the cortical cells released from the wool fibres. Hypothyroid sheep had slightly smaller follicle bulbs and dermal papillae than the control and hyperthyroid animals. The proportion of iding cells entering the fibre cortex (estimated from cortical cell volume, rate of fibre volume growth and rate of cell ision) was depressed by thyroidectomy suggesting that relatively more iding cells entered the inner root sheath in the follicles of hypothyroid sheep. This is supported by the lower production ratio (ratio of area of fibre to area of fibre-plus-inner root sheath) of the hypothyroid sheep. It is concluded that the rate of fibre elongation is depressed in hypothyroid sheep as a result of both a reduction in the rate of ision of cells in the follicle bulb and fewer of these iding cells entering the fibre cortex. This mechanism allows rapid changes in the rate of fibre elongation to occur with little change in the size of the follicle bulb, and may account for a number of scenarios in which fibre length changes rapidly with no concomitant change in fibre diameter. Fibre diameter, on the other hand, appears to be closely related to the dimensions of the follicle bulb, and by association, to the rate of bulb cell production. Selection of sheep with small follicle bulbs and at the same time, high production ratios, may be means of increasing fibre length whilst maintaining low fibre diameter.
Publisher: Wiley
Date: 03-2007
Publisher: The Company of Biologists
Date: 07-2009
DOI: 10.1242/DEV.031427
Abstract: A key initial event in hair follicle morphogenesis is the localised thickening of the skin epithelium to form a placode, partitioning future hair follicle epithelium from interfollicular epidermis. Although many developmental signalling pathways are implicated in follicle morphogenesis,the role of epidermal growth factor (EGF) and keratinocyte growth factor (KGF,also known as FGF7) receptors are not defined. EGF receptor (EGFR) ligands have previously been shown to inhibit developing hair follicles however, the underlying mechanisms have not been characterised. Here we show that receptors for EGF and KGF undergo marked downregulation in hair follicle placodes from multiple body sites, whereas the expression of endogenous ligands persist throughout hair follicle initiation. Using embryonic skin organ culture, we show that when skin from the sites of primary pelage and whisker follicle development is exposed to increased levels of two ectopic EGFR ligands (HBEGF and hiregulin) and the FGFR2(IIIb) receptor ligand KGF, follicle formation is inhibited in a time- and dose-dependent manner. We then used downstream molecular markers and microarray profiling to provide evidence that, in response to KGF and EGF signalling, epidermal differentiation is promoted at the expense of hair follicle fate. We propose that hair follicle initiation in placodes requires downregulation of the two pathways in question, both of which are crucial for the ongoing development of the interfollicular epidermis. We have also uncovered a previously unrecognised role for KGF signalling in the formation of hair follicles in the mouse.
Publisher: Elsevier BV
Date: 2011
Publisher: Elsevier BV
Date: 07-2016
Start Date: 2004
End Date: 12-2004
Amount: $386,892.00
Funder: Australian Research Council
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