ORCID Profile
0000-0002-4634-5819
Current Organisation
Murdoch University
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Publisher: Elsevier BV
Date: 2010
DOI: 10.1016/J.ANIREPROSCI.2009.03.011
Abstract: Our aim was to determine the role of opioidergic processes in the effects of nutrition on the secretion of LH pulses in the mature male sheep. In the first of three experiments, adult Merino rams were acclimatised to a maintenance diet and then allocated to one of three dietary groups (n=5): continuation of the maintenance diet (Group M) reduction to half of the maintenance allocation (Group HM) or supplementation of the maintenance diet with lupin grain (Group HD). An initial administration of naloxone (2mg/kg body weight, i.v.) was followed at 40-min intervals by three further administrations (1mg/kg). Blood was s led every 20 min for 12h before the initial naloxone administration and then for a further 6h. LH pulse frequency after naloxone treatment was significantly higher in Group HD than in Group HM (P<0.05). The second study tested whether the response to naloxone depended on calcium status. We used 22 adult Merino rams in two consecutive experiments, one in which the rams were fed a maintenance diet, and one in which the rams were fed with the maintenance diet plus 1 kg lupin grain for 5 weeks. In both experiments, rams were allocated to groups that received one of the following treatments: (a) 0.02 g/kg calcium borogluconate+0.2mg/kg naloxone hydrochloride (Nal+Ca(2+) n=6) (b) 0.2mg/kg naloxone hydrochloride (Nal n=6) (c) 0.02 g/kg calcium borogluconate (Ca(2+) n=5) (d) 0.1 ml/kg NaCl 0.9% (Saline n=5). All treatments were given as a single i.v. administration daily for 5 days. Blood was s led every 20 min for 24 h during the acclimatization period (Day 0) and on the last day (Day 5) of treatment. In the first study (under maintenance), none of the treatments affected LH pulse frequency. In the second study (the lupin-supplemented rams), LH pulse frequency was significantly increased (P<0.05) by the administration of naloxone+Ca(2+), naloxone alone and Ca(2+) alone. Overall, rams on a low plane of nutrition showed the smallest response to naloxone, suggesting that an opioidergic mechanism is not involved in the suppressive effect of restricted nutrition on the gonadotrophic axis. Rather, because testosterone secretion was increased on the high plane of nutrition, the LH responses to naloxone are better explained by the effects of testosterone on opioidergic mechanisms. Finally, we failed to observe any interaction between opioids and calcium in the control of LH secretion.
Publisher: Elsevier BV
Date: 05-2016
DOI: 10.1111/VAA.12311
Publisher: Bioscientifica
Date: 11-1997
Abstract: Corticotrophin-releasing hormone (CRH) has been proposed as a mediator of the antireproductive effects of stress through an action within the hypothalamus to inhibit GnRH secretion. This hypothesis was tested in sheep by studying the responses to central administration of CRH in both sexes and in both seasons. Sexually mature, Ile-de-France ewes and Romanov rams that had been gonadectomized and implanted with a permanent guide cannula into the third cerebral ventricle were used. Ewes were studied in the presence and absence of exogenous oestradiol plus progesterone, in both the breeding and anoestrous seasons. All rams were treated with testosterone and were studied only during the breeding season. Each observation involved serial s les (every 10 min) of jugular blood for 5 h before (control) and 5 h after an intracerebroventricular (i.c.v.) injection of either saline (vehicle) or 5 nmoles CRH in 20 microliters vehicle. The saline injections did not affect any of the endocrine variables measured however, CRH always increased cortisol concentrations in jugular plasma. In the absence of treatment with replacement sex steroids, icv injection of CRH had no effect on pulsatile LH secretion in females either during the breeding season or during anoestrus. However, LH pulse frequency and mean LH concentrations increased significantly on every occasion on which animals were treated with sex steroids. Treatment with CRH also increased LH secretion in the testosterone-treated rams. It is concluded that, contrary to the hypothesized role of CRH as an inhibitor of reproductive activity, this neuropeptide stimulates pulsatile LH (and thus GnRH) secretion, at least in this species. The fact that gonadal steroids seem to be obligatory for the expression of this effect suggests that the protocols used in past studies need to be reassessed.
Publisher: Cambridge University Press (CUP)
Date: 12-2008
DOI: 10.1017/S0954422408138744
Abstract: The central nervous system undertakes the homeostatic role of sensing nutrient intake and body reserves, integrating the information, and regulating energy intake and/or energy expenditure. Few tasks regulated by the brain hold greater survival value, particularly important in farmed ruminant species, where the demands of pregnancy, lactation and/or growth are not easily met by often bulky plant-based and sometimes nutrient-sparse diets. Information regarding metabolic state can be transmitted to the appetite control centres of the brain by a erse array of signals, such as stimulation of the vagus nerve, or metabolic ‘feedback’ factors derived from the pituitary gland, adipose tissue, stomach/abomasum, intestine, pancreas and/or muscle. These signals act directly on the neurons located in the arcuate nucleus of the medio-basal hypothalamus, a key integration, and hunger (orexigenic) and satiety (anorexigenic) control centre of the brain. Interest in human obesity and associated disorders has fuelled considerable research effort in this area, resulting in increased understanding of chronic and acute factors influencing feed intake. In recent years, research has demonstrated that these results have relevance to animal production, with genetic selection for production found to affect orexigenic hormones, feeding found to reduce the concentration of acute controllers of orexigenic signals, and exogenous administration of orexigenic hormones (i.e. growth hormone or ghrelin) reportedly increasing DM intake in ruminant animals as well as single-stomached species. The current state of knowledge on factors influencing the hypothalamic orexigenic and anorexigenic control centres is reviewed, particularly as it relates to domesticated ruminant animals, and potential avenues for future research are identified.
Publisher: CSIRO Publishing
Date: 2002
DOI: 10.1071/RD02010
Abstract: Rams of a 'Mediterranean breed' (Merino) and a 'temperate breed' (Suffolk) were compared to determine how much of the differences between their reproductive seasons is owing to variation in their responses to photoperiodic and nutritional cues. In a previous study, both nutritional and photoperiodic inputs were held constant, and it was found that the two breeds show similar endogenous rhythms and, when the animals are challenged with a Mediterranean photoperiodic cycle, these endogenous rhythms are similarly modified. The present study tested whether an annual cycle in the supply of forage might modify the patterns that are generated by the interaction between photoperiod and endogenous rhythms. Both breeds were subjected to a simulated `Mediterranean' annual cycle in photoperiod (10L : 14D to 14D : 10L) and provided with either constant food supply or a simulated `Mediterranean' annual cycle in food supply. In Merino rams, testicular growth responded to photoperiod, but nutrition dominated those responses. In Suffolk rams, changes in testicular size can be completely out of phase with changes in body mass because they are driven primarily by photoperiod, with only subtle responses to changes in diet. The cycle of testicular growth in the Suffolk was driven by changes in the secretion of gonadotrophins (follicle-stimulating hormone concentrations and luteinizing hormone pulse frequency). By contrast, in the Merino, the nutritionally driven seasonal cycle of testicular growth was associated primarily with changes in body mass and this relationship could not always be explained by changes in gonadotrophin secretion. Melatonin secretion was not affected by food supply. Thus, the `Mediterranean' and `temperate' genotypes have similar endogenous rhythms that are similarly modified by photoperiod but, with respect to seasonal changes in nutrition, they differ in both the nature of their reproductive response and the physiological mechanisms that mediate those responses.
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/AN13020
Abstract: Qualitative behavioural assessment (QBA) has been used to quantify the expressive behaviour of animals, and operant tests have been used to quantify measures of behavioural need. In this study we compared measures of behavioural expression and behaviour in operant tests. We examined the behavioural expression of pregnant ewes of body condition score (BCS) 2 and 3. The ewes were exposed to a feed motivation test in which they received a food reward. Pregnant ewes (48–70 days gestation) were assessed during a food motivation test after they had been maintained at BCS 3 (n = 7) or given a decreasing plane of nutrition that resulted in slow loss of 1 BCS unit (over 10–12 weeks n = 7) or a fast loss of 1 BCS unit (over 4–6 weeks n = 7). The feed motivation test involved ewes having the opportunity to approach a food reward and then being moved a given distance away from the reward by an automatic gate they could then subsequently return to the feeder. Continuous video footage of each ewe during one cycle of the gate (approaching and returning from the food reward) was shown in random order to 11 observers who used their own descriptive terms (free-choice profiling methodology FCP) to score the animals using QBA. Data of the assessment were analysed with generalised Procrustes analysis (GPA), a multivariate statistical technique associated with FCP. The research group also quantified the feeding behaviour of sheep in the same clips. These behaviours included how sheep approached the feeder, behaviours exhibited at the feeder, and how sheep returned from the feeder. There was consensus amongst observers in terms of their assessment of behavioural expression of the sheep (P 0.001). The GPA found three main dimensions of assessed behavioural expression in the sheep, which together explained 44% of the variation observed. GPA dimension 1 differed between the three treatment groups (P 0.05): ewes maintained at BCS 3 scored low on GPA dimension 1 (i.e. were described as more calm/bored/comfortable) compared with ewes that had a slow declining BCS (described as more interested/anxious/excited). GPA dimension 2 scores were not significantly different between treatment groups. However, quantitative behaviours exhibited by sheep during the clips were correlated with qualitative behavioural assessments made by the observers. Animals that spent more time ‘sniffing and looking for more feed’ were attributed lower GPA 2 scores (described as more hungry/searching/excited) (P 0.05), and animals that ‘did not walk directly to the food reward (but stopped along the way)’ were attributed significantly higher GPA 2 scores (more curious/intimidated/uneasy) (P 0.01). GPA dimension 3 scores also did not differ between the treatment groups however, sheep that had a higher number of feeding events during the entire 23-h feed motivation test were attributed lower GPA dimension 3 scores (they were described as more hungry/bold/interested) (P 0.05), and sheep that consumed a larger amount of the feed reward were attributed higher GPA dimension 3 scores (more curious/concerned/reserved) (P 0.05). We conclude that QBA is a valuable method of assessing sheep behavioural expression under the conditions tested, in that it provided an integrative characterisation of sheep behavioural expression that was in agreement with quantitative behavioural measures of feeding.
Publisher: S. Karger AG
Date: 10-12-2007
DOI: 10.1159/000112480
Abstract: Ghrelin is a circulating peptide, primarily secreted by the gut, that has reported actions within the hypothalamo-pituitary axis to stimulate food intake, inhibit GnRH/LH secretion and stimulate GH secretion in monogastric species. Here, we examine responses to centrally administered ghrelin in a seasonal ruminant. Estradiol-implanted castrated male sheep with indwelling intracerebroventricular (i.c.v.) cannulae were kept with unrestricted food for 16 weeks in long day photoperiod (LD, 16 h light/day) then 16 weeks in short days (SD, 8 h light/day). In week 16 of each photoperiod they were given a control (saline) i.c.v. injection on day 1 and ghrelin i.c.v. injection on day 2. Mean circulating endogenous plasma ghrelin concentrations showed no diurnal pattern and were similar between the photoperiods. Central ghrelin injection increased voluntary food intake 2-fold in the first hour after administration in LD but not in SD, decreased LH pulse frequency and litude in SD but not in LD, and stimulated GH release in both photoperiods, although there was a 1.5-fold larger response in LD. Therefore, central injection of ghrelin to sheep acutely stimulated food intake in LD, suppressed reproductive neuroendocrine output in SD, and stimulated GH secretion irrespective of photoperiod, although more pronounced in LD. These data indicate that photoperiod can influence hypothalamic appetite and reproductive neuroendocrine responses to ghrelin in seasonal species.
Publisher: Wiley
Date: 12-2019
DOI: 10.1111/VCP.12806
Abstract: Synthetic colloid solutions, administered by rapid infusion to volume-depleted dogs, might be present in high concentrations in subsequent urine s les. The potential for these solutions to affect the performance of ELISA measurements due to s le matrix effects when studying kidney injury biomarkers requires investigation. We aimed to investigate two different synthetic colloid solutions, 4% succinylated bovine gelatin (GEL) and 6% hydroxyethyl starch (HES), for potential interferences with a commercially available canine neutrophil gelatinase-associated lipocalin (NGAL) ELISA. Assay interference was assessed by measuring the linearity of NGAL concentrations measured using a canine NGAL ELISA after serial dilution of a canine pooled urine s le with an assay diluent, GEL, or HES. NGAL recovery from urine specimens containing up to 75% HES and up to 62.5% GEL was within acceptable limits (80%-120%). NGAL recovery from the urine specimen containing 75% GEL was poor (76%). Linear regression analysis demonstrated excellent linearity under dilution when a canine urine s le was diluted with the assay diluent, GEL, or HES. The presence of large amounts (>62.5%) of GEL in canine urine s les could cause negative interference in the performance of the NGAL ELISA investigated.
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/AN17588
Abstract: High lamb mortality continues to be a significant economic and welfare problem within the Australian sheep industry, with 20–30% of lambs born in commercial flocks dying mostly within 3 days of birth. Clinical hypocalcaemia and hypomagnesaemia cause ewe mortality, and, subsequently, either fetal or lamb death, but it is not known whether subclinical deficiencies of calcium (Ca) and magnesium (Mg) compromise lamb survival. This review considers the potential mechanisms through which Ca and Mg deficiencies may influence lamb survival, and factors influencing the risk of deficiency. Pastures grazed by lambing ewes may be marginal in calcium (Ca & g/kg DM) and magnesium (Mg & .9 g/kg DM) but also have a high dietary cation–anion difference (& meq/100 g DM) and high concentrations of potassium (K & g/kg DM) and nitrogen. In young cereal crops, sodium concentrations are also often low (& .9 g/kg DM). This combination of minerals and other nutrients creates an imbalance in supply and increases susceptibility to acute Ca (hypocalcaemia) and Mg (hypomagnesaemia) deficiency. Calcium is required for smooth muscle function and has a direct role in uterine contraction, so may influence the duration of parturition. Low Ca and Mg intake both influence insulin release and sensitivity, low Mg results in poor glycaemic control and insulin resistance by impairing both insulin secretion and its action on peripheral tissues, also potentially altering the duration of parturition as well as risk of metabolic disease. Magnesium is also a neuroprotectant that slows the neuronal damage during hypoxia and has been linked with thermogenesis in offspring and increased immunoglobulins in colostrum. These functions indicate potential importance in improving the ease of parturition and improved ability of the newborn lamb to thermoregulate and survive after birth. Subclinical Ca and Mg deficiencies commonly occur in 20% of lambing ewes grazing temperate pastures, so further studies are warranted to investigate whether correction of these deficiencies can improve lamb survival.
Publisher: Elsevier BV
Date: 04-2012
DOI: 10.1016/J.EXPPARA.2012.01.014
Abstract: Cryptosporidium is an enteric parasite of public health significance that causes diarrhoeal illness through faecal oral contamination and via water. Zoonotic transmission is difficult to determine as most species of Cryptosporidium are morphologically identical and can only be differentiated by molecular means. Transmission dynamics of Cryptosporidium in rural populations were investigated through the collection of 196 faecal s les from diarrheic (scouring) calves on 20 farms and 63 faecal s les from humans on 14 of these farms. The overall prevalence of Cryptosporidium in cattle and humans by PCR and sequence analysis of the 18S rRNA was 73.5% (144/196) and 23.8% (15/63), respectively. Three species were identified in cattle Cryptosporidium parvum, Cryptosporidium bovis and Cryptosporidium ryanae, and from humans, C. parvum and C. bovis. This is only the second report of C. bovis in humans. Subtype analysis at the gp60 locus identified C. parvum subtype IIaA18G3R1 as the most common subtype in calves. Of the seven human C. parvum isolates successfully subtyped, five were IIaA18G3R1, one was IIdA18G2 and one isolate had a mix of IIaA18G3R1 and IIdA19G2. These findings suggest that zoonotic transmission may have occurred but more studies involving extensive s ling of both calves and farm workers are needed for a better understanding of the sources of Cryptosporidium infections in humans from rural areas of Australia.
Publisher: Oxford University Press (OUP)
Date: 25-06-2020
DOI: 10.1093/JAS/SKAA190
Abstract: Dietary tryptophan (Trp) is a precursor for serotonin, a neuromediator involved in stress responses. Tryptophan competes with other large neutral amino acids (LNAA: tyrosine, isoleucine, leucine, valine, and phenylalanine) to cross the blood–brain barrier therefore, the regulation of circulating LNAA can influence Trp availability in the cortex and serotonin biosynthesis. The hypothesis examined in this study was that increased supplementation of dietary Trp and a reduction in LNAA for weaned pigs experimentally infected with enterotoxigenic Escherichia coli (ETEC F4) will increase Trp availability in plasma and reduce indices of the stress response, which will translate to reduced production losses. At 21 ± 3 d of age (mean ± SEM), 96 male pigs (Large White × Landrace) weighing 6.3 ± 0.98 kg (mean ± SEM) were in idually penned and allocated to a 4 × 2 factorial arrangement of treatments, with respective factors being 1) four dietary standardized ileal digestible (SID) Trp and LNAA contents, being HTrpHLNAA (Low Trp-High LNAA 0.24% SID Trp: 5.4% SID LNAA), HTrpHLNAA (Low Trp-Low LNAA 0.24% SID Trp: 4.6% SID LNAA), HTrpHLNAA (High Trp-High LNAA 0.34% SID Trp: 5.4% SID LNAA), and HTrpHLNAA (High Trp-Low LNAA 0.34% SID Trp: 4.6% SID LNAA), and 2) without/with ETEC infection. Pigs were orally infected with 0.8 mL (3.6 × 109 CFU/mL) ETEC at days 7 and 8 after weaning. Pigs fed diets high in Trp irrespective of the level of LNAA (HTrpHLNAA and HTrpLLNAA) had higher plasma Trp concentrations (P & 0.001) and a Trp:LNAA ratio (P & 0.001) before infection and 6 d after infection. Following infection, noninfected pigs had higher plasma Trp (P = 0.03) and a Trp:LNAA ratio (P = 0.004) compared with pigs infected with ETEC. Plasma cortisol levels after infection were higher in ETEC-infected pigs (P = 0.05) and altering dietary Trp and LNAA concentrations did not influence (P & 0.05) plasma cortisol. Pigs fed diet HTrpLLNAA had higher serum serotonin levels 24 h after infection (P = 0.02) compared with pigs fed diets LTrpLLNAA and HTrpHLNAA. Similarly, pigs fed diet HTrpLLNAA had a higher (P = 0.02) average daily gain during the 3-wk study. Overall, average daily feed intake tended to be higher in pigs fed an HTrpLLNAA diet compared with the other diets (P = 0.08). These results suggest that the increased supplementation of dietary Trp with reduced LNAA increased circulating Trp levels that, in turn, likely caused higher serum serotonin levels, irrespective of infection with ETEC, and improved aspects of post-weaning performance.
Publisher: Bioscientifica
Date: 12-2001
Abstract: Gonad development in female sheep fetuses is thought to occur in a number of key stages. The aim of this study was to determine the effects of maternal undernutrition, applied at one or more of these critical stages, on fetal ovarian development. Groups of ewes (n = 11-19) were fed rations providing either 100% (high H) or 50% (low L) of energy requirements for live weight maintenance during selected 'windows' during gestation. Control ewes (HH and HHH) were fed the H ration from mating until they were killed at days 50, 65 (HH) or 110 (HHH) of gestation, whereas ewes of other groups were fed the L ration for the periods between day 0 and day 30 of gestation (LH and LHH), day 31 and day 50 or 65 of gestation (HL and HLH), day 65 and day 110 of gestation (HHL) or day 0 of gestation until the animals were killed (LL and LLL). At day 50 of gestation, there was no effect of nutritional treatment on mean fetal mass but compared with HH animals, mean fetal ovarian mass was significantly lower in HL (P 0.05) and LL (P 0.001) animals. At day 65 of gestation, there were significantly fewer germ cells (P 0.05) at the resting, diplotene stage of initial meiosis in LL animals than there were in HH animals, indicating delayed germ cell maturation and onset of meiosis. Qualitative assessment of proliferative cell nuclear antigen immunostaining indicated that, at day 50 of gestation, staining was located predominantly in the germ cells, whereas by day 65 of gestation, staining was confined predominantly to somatic cells. Undernutrition in each one of these windows was associated with delayed ovarian follicular development (P 0.05-0.001) as measured by development of the granulosa cell layer at day 110 of gestation. This study demonstrates that undernutrition before and during folliculogenesis can delay fetal follicular development.
Publisher: Elsevier BV
Date: 07-2002
DOI: 10.1016/S0378-4320(02)00068-4
Abstract: The aim of this study was to determine the effects of maternal undernutrition during pregnancy on adult reproductive function in male and female offspring. Groups of ewes were fed rations providing either 100% (High, H) or 50% (Low, L) of estimated metabolisable energy (ME) requirements for pregnancy, from mating until day 95 of gestation, and thereafter were conventionally managed. At 20 months of age, LH and FSH profiles, and LH responses to exogenous GnRH were measured in male and female offspring and, in males, testicular responses to exogenous LH (as measured by testosterone concentrations) were also measured. Undernutrition had no effect on the mean birth weights of lambs of either sex, or on testicular size in male animals at either 6 weeks or 20 months of age. L males exhibited significantly higher FSH concentrations than H males (P < 0.05) but there were no differences with treatment in FSH profiles in females, basal LH profiles or gonadotrophin responses to GnRH in offspring of either sex, and no difference in basal testosterone concentrations or in the testosterone response to exogenous LH administration in males. Semen quality at 20 months of age was unaffected by pre-natal undernutrition but ovulation rate was significantly reduced in L compared to H female offspring (P < 0.05). It is concluded that pre-natal undernutrition had no effect on male reproductive development and adult function, but reduced ovulation rate in female progeny. This effect was not associated with a change in gonadotrophin profiles or pituitary responsiveness.
Publisher: Elsevier BV
Date: 02-2020
Publisher: Elsevier BV
Date: 08-2017
DOI: 10.1016/J.VPRSR.2017.05.001
Abstract: Faecal shedding of Eimeria by captured rangeland goats (Capra hircus) was investigated using a longitudinal observational study. Faecal s les were collected from 125 male goats on four occasions. The first s ling occurred following capture and transport, immediately after arrival at a commercial goat depot (feedlot) in Western Australia, with subsequent 3 s le collections occurring at one month intervals thereafter. Goats were composite breed and aged approximately 9-12months on arrival at the feedlot. Prevalence and shedding intensity (faecal oocyst concentration) for Eimeria were determined using qPCR. Species were identified from in idual oocysts (isolated using micromanipulation) using molecular analysis at two loci, specifically 18S rRNA and mitochondrial cytochrome oxidase gene (COI), and confirmed by microscopy. Longitudinal prevalence (animals positive at least once) for Eimeria spp. by qPCR was 90.4%, with 60% goats shedding Eimeria spp. on more than one occasion. Point prevalence (prevalence at a single s ling occasion) ranged from 2.4% (fourth s ling) to 70.4% (second s ling). Three species were identified at the 18S rRNA locus and confirmed by microscopy: E. christenseni (longitudinal prevalence for single infection 34.4%), E. hirci (17.6%) and E. arloingi (8.8%) over the four s le collections. Mixed infections were identified in 56.8% goats (longitudinal prevalence). 18S rRNA sequences from E. christenseni and E. hirci were 100% homologous with ovine E. ahsata and E. crandallis respectively, and E. arloingi was 100% similar to caprine E. arloingi. At the COI locus, E. christenseni, E. hirci and E. arloingi grouped separately, and were closely related to ovine E. ahsata, with genetic similarities of 96.5%, 92.6% and 91.4% respectively. This is the first report for molecular characteristics of caprine-derived Eimeria spp. using a combination of 18S rRNA and COI. Molecular techniques can be used to identify Eimeria spp. in goat faecal s les, specifically through characterization at 18S locus and other gene loci when used in parallel. Molecular techniques offer some advantages over microscopy for identification of Eimeria species, particularly with respect to precision.
Publisher: American Dairy Science Association
Date: 04-2012
Abstract: The effects of grain, fructose, and histidine on ruminal pH and fermentation products were studied in dairy cattle during an induced subacute acidosis protocol. Thirty Holstein heifers were randomly allocated to 5 treatment groups: (1) control (no grain) (2) grain [fed at a crushed triticale dry matter intake (DMI) of 1.2% of body weight (BW)] (3) grain (0.8% of BW DMI)+fructose (0.4% of BW DMI) (4) grain (1.2% of BW DMI)+histidine (6 g/head) and (5) grain (0.8% of BW DMI)+fructose (0.4% of BW DMI)+histidine (6 g/head) in a partial factorial arrangement. Heifers were fed 1 kg of grain daily with ad libitum access to ryegrass silage and alfalfa hay for 10 d. Feed was withheld for 14 h before challenge day, on which heifers were fed 200 g of alfalfa hay and then the treatment diets immediately thereafter. Rumen s les were collected 5 min after diet ingestion, 60 min later, and at 3 subsequent 50-min intervals. Grain decreased ruminal pH and increased ammonia, total volatile fatty acid (VFA), acetate, butyrate, propionate, and valerate concentrations compared with controls. The addition of grain had no effect on ruminal D- and L-lactate concentrations. Fructose markedly decreased ruminal pH and markedly increased D- and L-lactate concentrations. Fructose increased total VFA and butyrate and decreased valerate concentrations. Although histidine did not have a marked effect on ruminal fermentation, increased concentrations of histamine were observed following feeding. This study demonstrates that the substitution of some grain for fructose can lower ruminal pH and increase VFA and lactate concentrations, warranting further investigation into the role of sugars on the risk of acidosis in dairy cattle.
Publisher: Elsevier BV
Date: 05-1993
Publisher: Informa UK Limited
Date: 19-02-2015
DOI: 10.1080/10888705.2015.1005302
Abstract: We tested the application of qualitative behavioral assessment (QBA) as a welfare assessment tool. Sheep were exposed to road transport treatments, and behavioral expressions were compared between experimental treatments and validated by correlation with physiological measures. We compared journeys differing in ventilation (closed vs. open-sided trailer), flooring (grip vs. nongrip flooring), and driving styles (stop-start vs. continuous driving). Blood s les were collected immediately before loading and after unloading heart rate and core body temperatures were recorded continuously. Continuous video footage was edited to show in idual sheep to observers for QBA using free-choice profiling (observers used their own descriptive terms). There was significant consensus in observers' scores for the sheep in each experiment (p < .001). Observers distinguished between sheep exposed to flooring (p = .014) or driving-style (p = .005) treatments, but not between ventilation treatments. QBA scores were compared (p < .05) with plasma leptin, glucose, and insulin-like growth factor-1 concentrations white blood cell profiles red blood cell counts hematocrit body temperatures and heart rate variability. Observer assessments reflected treatment differences, and correlations between behavioral expression and physiological responses were found.
Publisher: Springer Science and Business Media LLC
Date: 27-06-2007
Abstract: Ghrelin is an orexigenic hormone principally produced by the stomach, but also by numerous peripheral tissues including the placenta. Ghrelin acts via growth hormone secretagogue receptors (GHSR-1a) to alter food intake, fat utilization, and cellular proliferation, and has been suggested to play a role in the developmental growth of the fetoplacental unit. The placental expression of ghrelin and its role in ruminant species is not known. We tested the hypotheses that ghrelin and its functional receptor, GHSR-1a, are present in tissues of the ovine placenta, and that their expression is linked to the stage of development. Antibodies raised against ghrelin and GHSR-1a were used in standard immunohistochemical protocols on placental tissues collected from pregnant ewes (n = 6 per gestational time point) at days 50, 80, 100, 128 and 135 of gestation (term ≈ day 145). Immunostaining for ghrelin and GHSR-1a was quantified using computer-aided image analysis. Image analysis data were subjected to one-way ANOVA, with differences in immunostaining between time-points determined by Fisher's least significant difference. Positive immunostaining for ghrelin was detected in ovine placentae at all gestational time points, with staining localized to the maternal epithelium, caruncle and trophectoderm. There was a significant effect of gestational age (p 0.001) on the placental expression of ghrelin, with maximal levels at gestational day 80. GHSR-1a immunostaining was detected in the fetal trophectoderm at all time points. In contrast to the gestational pattern of ghrelin expression, there was no effect of gestational age on placental GHSR-1a immunoexpression. Ghrelin and GHSR-1a are both present in the ovine placenta, and ghrelin displays a developmentally-related pattern of expression. Therefore, these data strongly suggest that the ghrelin system may have a role in feto-placental development in sheep.
Publisher: Bioscientifica
Date: 07-2002
Abstract: The aim of this study was to determine the effects of maternal undernutrition, applied during physiologically relevant stages of development of the reproductive system, on reproductive development in male sheep fetuses. Groups of ewes (n = 11-19) were fed rations providing either 100% (high H) or 50% (low L) of metabolizable energy requirements for live weight maintenance during selected 'windows', bounded by days 0, 30, 50, 65 and 110 after mating. Ewes of control groups (HH (Expts 1 and 2) and HHH (Expt 3)) were fed the H ration from mating until they were killed at day 50 (Expt 1), day 65 (Expt 2) or day 110 (Expt 3) of gestation, whereas ewes of other groups were fed the L ration for the periods days 0-30 of gestation (LH and LHH), days 31-50 or days 31-65 of gestation (HL and HLH), days 65-110 of gestation (HHL), or day 0 to day 50, day 65 or day 110 of gestation (LL and LLL) when the animals were killed. At day 50 of gestation, there was no effect of nutritional treatment on mean fetal mass or fetal testicular mass, but there was increased expression of mRNA for steroidogenic acute regulatory protein (StAR) in the testes of LL animals (P 0.05) compared with HH controls. Compared with HH animals, the mean plasma testosterone concentrations of LL fetuses tended to be higher, but this result did not reach significance. At day 65 of gestation there were no significant differences between treatments in mean fetal masses, testicular masses, mean plasma testosterone concentrations or StAR mRNA content. At day 110 of gestation, fetal masses in the LLL group were lower (P 0.01) than those of control fetuses, although no differences in testicular size or fetal plasma testosterone concentrations were recorded. It is concluded that the effects of undernutrition on reproductive development of male sheep fetuses are dependent on the timing of the period of undernutrition.
Publisher: Bioscientifica
Date: 11-1995
Abstract: The effect of nutrition on gonadotrophin secretion may be exerted through a central metabolic signal that reflects nutritional status. We have previously found that glucose and insulin concentrations are elevated in the cerebrospinal fluid (CSF) of rams in which the secretion of gonadotrophins has been stimulated by a nutritional supplement of lupin grain ( Lupinus angustifolius ). In the present study, we tested the hypothesis that insulin and/or glucose is a metabolic modulator of GnRH secretion and mediates the effects of nutrition on gonadotrophin secretion. Six mature rams were fed a diet that maintained live weight and then given a series of infusions, each for 12 h/day for 4 days, in a cross-over design. The treatments were: artificial CSF (aCSF), glucose (50 μmol/h) in aCSF, insulin (0·6 ng/h) in aCSF, and glucose (50 μmol/h) plus insulin (0·6 ng/h) in aCSF all infused at a rate of 5 μl/min. At the same time as the infusion treatments, two other groups of four rams without cerebral cannulae were fed either the maintenance diet or the same diet supplemented with 750 g lupin grain per head per day for 4 days, again in a cross-over design. Rams fed the lupin supplement showed an increase in both LH pulse frequency and mean FSH on day 4 ( P ·05). Infusion of aCSF or glucose did not affect gonadotrophin secretion. Rams infused with insulin or insulin plus glucose showed an increase ( P ·05) in LH pulse frequency but no increase in FSH concentrations on day 4 of infusion. The magnitude of the LH response to insulin was similar to the nutritional response of feeding lupin supplements. There was no effect of any of the infusion treatments on plasma prolactin or insulin secretion. These data show that changes in insulin concentrations in the CSF lead to changes in LH secretion and support the hypothesis that insulin is a metabolic modulator of GnRH secretion and mediates the effects of nutrition on gonadotrophin secretion. Journal of Endocrinology (1995) 147, 321–329
Publisher: MDPI AG
Date: 15-11-2018
DOI: 10.3390/ANI8110209
Abstract: Land transport is an unavoidable experience for most livestock, yet there is limited research comparing animal welfare under different conditions. We video recorded sheep responses during short (2 h) commercial road transport journeys. Using Qualitative Behavioural Assessment, observers (blinded to the treatments) scored the behavioural expression of sheep and reached significant consensus in their scoring patterns (p 0.001). There were also significant effects of vehicle crate design (sheep transported in a ‘standard’ crate were more calm/relaxed than those transported in a ‘convertible’ crate), deck position (sheep on upper decks were more curious/alert than those on lower decks), and sheep breed (fat-tail sheep were more agitated/distressed than merino sheep) on observer scores. We only found marginal differences for sheep originating from feedlot or saleyard. Significant effects of vehicle driver (included as a random factor in all but one of our analyses) suggest driving patterns contributed to demeanour of the sheep. Finally, the fourteen drivers who participated in the study were asked their opinions on livestock transport none of the factors we tested were identified by drivers as important for sheep welfare during transport. This study supports the use of qualitative measures in transport and revealed differences that could inform truck design.
Publisher: Oxford University Press (OUP)
Date: 06-01-2018
Publisher: CSIRO Publishing
Date: 2013
DOI: 10.1071/AN12143
Abstract: This study investigated the effect of nutrition on wool harvesting efficiency of a biological wool harvesting system (Bioclip) utilising epidermal growth factor (EGF) to induce shedding of the fleece. The experiment had nine groups, each representing a different growth path based on a 3 by 3 design with three levels of nutrition (low, medium and high) fed during two periods, specifically the pre-injection period (4-weeks leading up to EGF injection) and post-injection period (4 weeks between EGF injection and wool harvesting). Sheep weight and body condition score were measured at the start and end of each period. Wool harvesting efficiency, fleece weight and body wrinkle were assessed at wool harvesting. Continuous data were analysed using general linear models and linear regression. Bivariate categorical data were analysed using Chi-squared tests and odds ratios. Wool harvesting efficiency was reduced in sheep with greater skin wrinkle (P 0.001), poorer body condition (P 0.001) and poorer nutrition in both pre- and post-injection periods (P 0.001). Sheep that gained 1 kg bodyweight or 0.5 body condition score either pre- or post-injection had improved wool harvestability (P 0.05). Sheep that lost weight post-injection were 10.2 (95% confidence interval 4.0, 25.5) times and 4 times (2.4, 6.7) more likely to have very poor harvestability compared with sheep that gained or maintained weight respectively (P 0.001). Sheep with greater body wrinkle were 6.6 (4.1, 10.7) times more likely to have very poor harvestability than plain-bodied sheep (P 0.001). Nutrition that ensures modest weight gain during the pre- and post-injection periods can partially overcome poorer harvestability in wrinkly sheep.
Publisher: The Endocrine Society
Date: 10-2006
DOI: 10.1210/EN.2006-0576
Abstract: Impaired anorectic actions of leptin may be due to intrahypothalamic insensitivity and/or reduced blood-brain transport. The influence of photoperiod on leptin responses and leptin transport from blood into cerebrospinal fluid (CSF) was examined in sheep. Sheep kept on ad libitum food for 15 wk in long days (LD) had higher voluntary food intake and lower GnRH/LH output than in short days (SD). Food intake was decreased approximately 30% after intracerebroventricular (icv) (and not iv) leptin injection, but only in SD. GnRH/LH secretion was decreased after icv (but not iv) leptin in both photoperiods. Leptin concentrations in CSF were higher in LD than SD but correlated with plasma leptin only in LD. Amounts of leptin entering CSF after iv leptin injection were greater in LD than SD. In a separate experiment, plasma (but not CSF) leptin was higher in fat than thin sheep in natural summer LD and after 5 wk in SD. CSF leptin correlated with plasma leptin in LD but not SD. CSF leptin after iv leptin injection was higher in thin than fat sheep but only in LD. Endogenous CSF to plasma concentration ratios correlated negatively with plasma concentrations, indicating decreased blood-brain transport with increased leptinemia. Therefore, icv (and not iv) leptin inhibited appetite only in SD and decreased GnRH/LH output in both photoperiods, and the proportion of circulating leptin entering CSF was higher in LD and thinner animals. Photoperiod apparently modulates intrahypothalamic leptin sensitivity of appetite, but not reproductive, regulatory pathways, whereas photoperiod and leptinemia influence leptin blood-brain transport.
Publisher: Wiley
Date: 13-05-2010
Publisher: Informa UK Limited
Date: 28-08-2018
DOI: 10.1080/10888705.2017.1363651
Abstract: Across the globe, producers are moving from in idual housing to group housing for sows during gestation. Producers typically group sows of a range of parities together, although the impacts are largely unknown. This study examined the behavioral expression at mixing for young, midparity, and older sows. Ten mixed-parity groups were filmed at mixing on a commercial piggery. One-minute clips were edited from continuous footage where focal sows of known parity could be identified, and scored for qualitative behavioral expression. Parity 2 and 6 sows were more calm/tired than Parity 4 sows, who were more active/energetic. Parity 2 sows were more curious/inquisitive than Parity 4 and 6 sows, who were more anxious/frustrated. Correlations between qualitative behavioral expression and activity indicated sows scored as more calm/tired spent a greater proportion of time standing, while sows scored as more active/energetic spent more time performing avoidance behavior. Different body language is likely to reflect physical or affective differences in how sows cope with mixing.
Publisher: MDPI AG
Date: 17-04-2020
DOI: 10.3390/ANI10040705
Abstract: Australian livestock industries face increased scrutiny from animal welfare groups and society, and the long-distance transport of livestock by sea has recently gained particular attention. Other than non-compliance with broad regulatory standards and voyage mortality rates, there is minimal information to ascertain the welfare of exported livestock. There is currently no standardised, validated animal welfare assessment protocol for livestock on-farm prior to live export or when undergoing transport. This study describes a novel assessment protocol suitable for use on live feeder and slaughter animals exported by sea from Australia. Health and welfare indicators for use in the livestock export supply chain were identified by reviewing three internationally recognised animal welfare assessment protocols for livestock Welfare Quality®, AWIN and AssureWel, as well as consulting with industry compliance standards and guidelines. This paper proposes a welfare protocol designed to assess sheep and beef cattle exported by sea from Australia, and incorporates environmental-, resource-, management- and animal-based measures. In collaboration with industry, this welfare protocol can be tested on commercial livestock consignments, and be used for ongoing management, for increased transparency and to provide feedback to operators for continuous improvement.
Publisher: CSIRO Publishing
Date: 2011
DOI: 10.1071/AN10122
Abstract: The present study examined whether observers could distinguish between cattle that are naïve to road transport and the same cattle after becoming more habituated to transport. The behavioural expression of cattle was assessed through the method of qualitative behavioural assessment (QBA), and these assessments were correlated with various physiological parameters. Fourteen Angus steers were assessed during their first road trip and then again on their ninth trip, 15 days later. Blood s les were collected immediately before and after transport, and heart rate and core body temperature were measured continuously throughout each trip. Video footage recorded during each trip was edited and clips showing each in idual within the first 30 min of departure were randomly ordered and shown to observers for QBA. There was significant (P 0.001) consensus among 40 observers in their assessment of behavioural expression of the cattle. Transport-naïve cattle were described as more ‘agitated’, while transport-habituated were described as more ‘calm’. Core body temperature (P 0.01), plasma glucose (P 0.05) and the neutrophil : lymphocyte ratio (P 0.01) were higher for the first trip than for the habituated trip (P 0.01). QBA were significantly correlated with core body temperature (P 0.01), heart rate (P 0.01), plasma glucose (P 0.05) and the neutrophil : lymphocyte ratio (P 0.01). QBA appears to be a valid and integrative method of assessing cattle welfare under the conditions tested within the present study. There was significant consensus in the ability of human observers to interpret behavioural expression of cattle during this experiment. In addition, observers could identify differences in behavioural expression between cattle that were naïve versus habituated to transport, and these differences were supported by physiological measurements.
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/AN15132
Abstract: The behaviour of intensively managed sows is influenced by the design of their housing, with the physical structure of the pen affecting how sows spend their time. The first hour after unfamiliar sows are mixed into group housing is considered important in terms of their welfare due to high levels of aggression as they develop a hierarchy and investigate their new surroundings and pen-mates. This study compared the behaviour of sows on a commercial piggery at the point of mixing into 20 group pens (n = 15–18 sows each group), where half the group pens had a concrete partition (a short wall, 2 m long and 1.6 m high) running through the middle of the pen, and half did not have the partition. We predicted that the partition would improve the expression of behaviours during the first hour after mixing. Sows were filmed for 70 min post-mixing and the footage was analysed using quantitative behavioural profile for eight behavioural categories (i.e. time budgets). We found no significant differences in the incidence of aggression, but found less investigative behaviour for sows in pens with the partition these sows also lay down sooner compared with sows in no-partition pens, and stopped eating/searching for food sooner. The difference between pen designs was most evident at 50–60 min post-mixing, and therefore we compared the behavioural expression of the sows using qualitative behavioural assessment for this time point. There was significant inter-observer reliability among the 17 observers, with 60.02% (P 0.001) of the variation in their scoring using the Free Choice Profiling methodology explained by the consensus profile. Sows in partition pens were scored as more ‘calm/relaxed’ compared with sows in no-partition pens, which were scored as more ‘aggressive/tense’. There were also significant correlations between the time budgets and behavioural expression scores, with groups of animals described as more ‘aggressive/tense’ also showing more walking, aggression, and avoidance, but less lying. The sows described as more ‘sleepy/bored’ showed more lying and sitting. This study shows that even a subtle difference in housing design (in this case, retention of a concrete partition) can make a significant positive difference to the demeanour and activity patterns of sows. Identifying housing designs that have positive welfare outcomes can inform pen design and construction, and is particularly relevant where housing is being converted (e.g. from single pens to group housing) and decisions must be made around whether or not to keep existing structures.
Publisher: Oxford University Press (OUP)
Date: 09-2011
Abstract: The objective of this study was to evaluate whether altering the timing of the secondary anti-gonadotropin-releasing factor (GnRF) immunization closer to slaughter in male finishing pigs would reduce the increase in P2 fat depth (6.5 cm from the midline over the last rib), while still limiting the incidence of boar taint. Entire male pigs are immunized against GnRF to reduce the concentration of testicular steroids that in turn limits the incidence of boar taint. Additionally, testicle measurements and color measurements were taken to examine whether they could be used to differentiate nonimmunized entire males from immunized male pigs. A total of 175 Large White × Landrace entire male pigs aged 16 wk (59 kg of BW) were used in a completely randomized design with 5 treatment groups based on the time that pigs received the secondary immunization before slaughter. Pigs were housed in groups of 7 and randomly allocated to 1 of 5 treatments with 5 replicates per treatment. The treatment groups were as follows: no secondary immunization before slaughter, and the secondary immunization given at 2, 3, 4, or 6 wk before slaughter. The P2 fat depth levels were reduced (P = 0.054) with the secondary immunization closer to slaughter (11.7, 11.3, 12.8, 12.6, and 13.7 mm for no secondary immunization, secondary immunization at 2, 3, 4, and 6 wk before slaughter, respectively). Androstenone concentration did not exceed the generally accepted industry sensory threshold of 1.0 µg/g of fat, and both androstenone concentration in the adipose tissue and testosterone concentrations in the blood were suppressed (P < 0.001) in all immunized pigs regardless of timing of the secondary immunization compared with pigs that did not receive the secondary immunization. Skatole concentration of all pigs in the experiment did not exceed the generally accepted industry sensory threshold of 0.2 µg/g. Testes weight was reduced (P < 0.001) with increased time between slaughter and the secondary immunization. Immunized pigs, regardless of time before slaughter, had greater L* (lightness) and b* (yellowness) color of the testicle surface (P < 0.001 and P = 0.020, respectively), and less a* (redness) color compared with entire males (P < 0.001). The study provides further evidence of the efficacy of the anti-GnRF immunization and indicates that the secondary immunization can be moved closer to slaughter, while still limiting the incidence of boar taint. Testicle measurements and color measurements together could provide a method of discrimination between carcasses from immunized entire males clear of boar taint and tainted carcasses.
Publisher: Elsevier BV
Date: 08-2018
DOI: 10.1016/J.VETPAR.2018.07.005
Abstract: Cryptosporidium and Giardia are common parasites of ruminant livestock worldwide. These parasites are associated with diarrhoea outbreaks in young goats (pre-weaning), but the impacts on health and productivity for older goats (post-weaning) are not well understood. Here we show Cryptosporidium faecal shedding is associated with reduced growth and diarrhoea in goats aged approximately 9-15 months. Goats were s led four times at one-month intervals. Faecal shedding for a range of pathogens were determined using quantitative PCR and sequencing (Cryptosporidium, Giardia, Eimeria, Salmonella, C ylobacter), and microscopy (trichostrongylid nematode worm egg count and Entamoeba). Cryptosporidium faecal shedding was associated with 1.5 kg lower growth for the one-month period following s ling. Specifically, C. xiaoi was associated with 1.9 kg lower growth in the following month. This is the first report of production impacts associated with C. xiaoi in ruminants older than 3 months of age. Cryptosporidium shedding was associated with an over 4-fold increase in risk of diarrhoea, with C. parvum associated with 10-fold and C. ubiquitum associated with 16-fold increase in risk of diarrhoea. Notably, C. xiaoi shedding was not associated with increased risk of diarrhoea. Giardia shedding was associated with looser faecal consistency, but not diarrhoea. Higher Eimeria oocyst counts were weakly associated with lower live weight, poorer body condition and looser faecal consistency. Shedding of other enteric pathogens were not associated with impacts on live weight, growth or diarrhoea risk. This study challenges the two notions that Cryptosporidium infections only impact health and productivity of goats during the pre-weaning period, and that Cryptosporidium (and specifically C. xiaoi) infections in the absence of diarrhoea are asymptomatic. Recognising the potential for impacts of Cryptosporidium infection on growth rates in the absence of diarrhoea will support improved design for experiments testing impacts of Cryptosporidium on ruminant health and production. Improved understanding of the role of protozoan infections on animal health has implications for the management of goats in order to reduce adverse impacts on farm profitability, animal welfare and public health risk.
Publisher: Elsevier BV
Date: 02-2017
DOI: 10.1016/J.VETPAR.2017.01.013
Abstract: Uninucleated Entamoeba cysts measuring 7.3×7.7μm were detected in faecal s les collected from wild Rangeland goats (Capra hircus) after arrival at a commercial goat depot near Geraldton, Western Australia at a prevalence of 6.4% (8/125). Sequences were obtained at the 18S rRNA (n=8) and actin (n=5) loci following PCR lification. At the 18S locus, phylogenetic analysis grouped the isolates closest with an E. bovis isolate (FN666250) from a sheep from Sweden with 99% similarity. At the actin locus, no E. bovis sequences were available, and the isolates shared 94.0% genetic similarity with E. suis from a pig in Western Japan. This is the first report to describe the morphology and molecular characterisation of Entamoeba from Rangeland goats in Western Australia and the first study to produce actin sequences from E. bovis-like Entamoeba sp.
Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/WR18105
Abstract: Context Temperament can affect an in idual’s fitness and survival if it also influences behaviours associated with predator avoidance, interactions with conspecifics, refuge selection and/or foraging. Furthermore, temperament can determine an in idual’s response to novel stimuli and environmental challenges, such as those experienced through translocation. Increasing our understanding of the effect of temperament on post-translocation fitness is thus necessary for improving translocation outcomes. Aims The aim was to test whether differences in an in idual’s behaviour or physiology could help predict body mass changes post-translocation in the woylie (brush-tailed bettong, Bettongia penicillata ogilbyi). In the absence of predation (due to release into a predator-free exclosure), body mass was used as a proxy for an in idual’s success in securing resources in the new habitat, and therefore fitness. Methods Forty woylies were translocated from two predator-free exclosures to a larger exclosure, all in Western Australia. Behavioural and physiological measures were recorded during trapping, processing, holding, and release, and again at re-capture ~100 days post-release. Key results Translocated woylies generally increased in body mass post-translocation. This suggests that, in the absence of predation, the selected candidates were able to cope with the stress of translocation and possessed the behavioural plasticity to successfully find resources and adapt to a novel environment. The strongest predictors of body mass gain were sex, heart rate lability and escape behaviour when released (a convoluted escape path). Conclusions There was no significant difference in body mass between males and females pre-translocation but females showed greater mass gain post-translocation than did males, which could reflect greater investment in reproduction (all females had pouch young). Heart rate lability and escape behaviour are likely to reflect reactivity or fearfulness, a significant temperament trait in the context of translocation success. Implications Behavioural measures that can be easily incorporated into the translocation process – without increasing stress or affecting welfare of in iduals – may hold promise for predicting the fate of translocated animals.
Publisher: Springer Science and Business Media LLC
Date: 17-07-2019
Publisher: Oxford University Press (OUP)
Date: 23-09-2019
DOI: 10.1093/JAS/SKZ303
Abstract: An infection model with enterotoxigenic Escherichia coli (ETEC) harboring the F4 fimbriae can be used to assess the impacts that various challenges associated with weaning (e.g., dietary, psychological, environmental) have on the expression of postweaning diarrhea. The objective of this study was to develop a novel inoculation method for administering an ETEC culture that would induce a higher proportion of ETEC-F4 diarrhea, in pigs that genetically showed ETEC-F4 susceptibility or resistance. The study was designed as a factorial arrangement of treatments with the factors being 1) partially susceptible or resistant to ETEC-F4 based on genetic testing, and 2) 4 challenge treatments, being a) a conventional liquid broth method using a drenching gun [Positive control (PC)], b) a Syringe method, c) a Capsule method, and d) Negative control [pigs not challenged (NC)]. At 21 ± 3 d of age (mean ± SEM), 48 male castrate pigs (Large White × Landrace) weighing approximately 7.0 ± 1.18 kg were allocated to 4 treatment groups in 2 replicate pens (6 pigs per pen). Initial ETEC-F4 susceptibility was based on a DNA marker test and each treatment group had 9 partially susceptible and 3 resistant pigs. On days 7 and 8 after weaning, pigs were challenged with ETEC (serotype O149:K88 toxins LT1, ST1, ST2, and EAST). On each inoculation day the PC pigs were orally dosed with 9 mL 7.12 × 109 colony-forming unit (CFU), the Syringe pigs with 0.8 mL 6.72 × 109 CFU, the Capsule pigs were orally administered 2 capsules containing 0.8 mL 3.28 × 109 CFU, and the NC pigs 1 mL of phosphate-buffered saline (PBS) solution. Approximately 72 h after infection, 44, 22, 78, and 0% of partially susceptible pigs in the PC, the Syringe, the Capsule, and the NC group had developed ETEC-F4 diarrhea (P = 0.007). Partially susceptible pigs had a higher diarrhea index (DI) compared to resistant pigs (31.5 vs. 4.8, P 0.001). The NC group had a lower DI compared to the PC and Capsule pigs (3.9, 38.1, and 40.3, respectively, P 0.005). Following infection, genetically resistant pigs in the Capsule group had a DI of zero and the partially susceptible pigs had a DI of 55.6 (P = 0.014). This study showed that genetically screening pigs and using a Capsule to deliver ETEC-F4 can increase cases of diarrhea and the efficiency of the challenge model. Taken together, these methods have the potential to reduce the number of pigs needed in future experimental infection studies.
Publisher: Oxford University Press (OUP)
Date: 25-01-2018
DOI: 10.1093/JAS/SKX004
Publisher: Elsevier BV
Date: 2018
Publisher: Elsevier BV
Date: 2017
DOI: 10.1016/J.VPRSR.2016.11.006
Abstract: Faecal shedding of Cryptosporidium and Giardia by captured rangeland goats was investigated using a longitudinal study with four faecal s les collected from 125 male goats once monthly for four months, commencing immediately after capture and transport to a commercial goat depot (feedlot). Goats were composite breed and aged approximately 9-12months on arrival. Faecal s les were screened for Cryptosporidium and Giardia presence and concentration using quantitative PCR and sequencing at the 18S ribosomal RNA locus (Cryptosporidium), and glutamate dehydrogenase and β-giardin loci (Giardia). Longitudinal prevalence for Cryptosporidium was 27.2% (point prevalence range 3-14%) with 3 species identified: C. xiaoi (longitudinal prevalence 13.6%), C. ubiquitum (6.4%) and C. parvum (3.2%). Sub-typing at the gp60 locus identified C. ubiquitum XIIa, C. parvum IIaA17G2R1 and C. parvum IIaA17G4R1. This is the first report of the zoonotic C. parvum subtype IIaA17G4R1 in goats. The pattern of genotypes shed in faeces changed over the duration of study with C. ubiquitum identified only at the first and second s lings, and C. parvum identified only at the fourth s ling. Longitudinal prevalence for Giardia duodenalis was 29.6% (point prevalence range 4-12%) with all positives sub-typed as assemblage E. Only 2/125 goats were identified to be shedding Cryptosporidium or Giardia on more than one occasion. This is the first report of Cryptosporidium and Giardia genotypes in captured rangeland goats. Faecal shedding of zoonotic Cryptosporidium spp. and potentially zoonotic G.duodenalis has implications for food safety and effluent management. Keywords: Cryptosporidium Giardia Rangeland goats zoonotic.
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/AN15101
Abstract: Animal welfare is increasingly important for the Australian livestock industries, to maintain social licence to practice as well as ensuring market share overseas. Improvement of animal welfare in the livestock industries requires several important key steps. Paramount among these, objective measures are needed for welfare assessment that will enable comparison and contrast of welfare implications of husbandry procedures or housing options. Such measures need to be versatile (can be applied under a wide range of on- and off-farm situations), relevant (reveal aspects of the animal’s affective or physiological state that is relevant to their welfare), reliable (can be repeated with confidence in the results), relatively economic to apply, and they need to have broad acceptance by all stakeholders. Qualitative Behavioural Assessment (QBA) is an integrated measure that characterises behaviour as a dynamic, expressive body language. QBA is a versatile tool requiring little specialist equipment suiting application to in situ assessments that enables comparative, hypothesis-driven evaluation of various industry-relevant practices. QBA is being increasingly used as part of animal welfare assessments in Europe, and although most other welfare assessment methods record ‘problems’ (e.g. lameness, injury scores, and so on), QBA can capture positive aspects of animal welfare (e.g. positively engaged with their environment, playfulness). In this viewpoint, we review the outcomes of recent QBA studies and discuss the potential application of QBA, in combination with other methods, as a welfare assessment tool for the Australian livestock industries.
Publisher: Bioscientifica
Date: 2006
DOI: 10.1530/REP.1.00844
Abstract: This study aimed to determine whether reduced fetal ovary folliculogenesis in ewes undernourished during early/midpregnancy is associated with altered ovarian cell proliferation and/or the expression of apoptosis-regulating genes. Groups of ewes ( n = 11–19) were fed either 100% (high H) or 50% (low L) of metabolisable energy requirements for live-weight maintenance during selected windows of gestation. All animals were killed at days 50, 65 or 110 of gestation. Between mating and slaughter, control animals were fed the H ration, while animals of other subgroups were fed the L ration from (a) mating to slaughter at 50, 65 or 110 days (b) 0 to 30 days (c) 31 to 50 or 65 days or (d), in the day 110 slaughter group only, from 66 to 110 days. Bouin’s-fixed fetal ovaries were examined for (a) Ki67 immunoexpression (proliferation) and (b) Bax and Mcl-1 (apoptosis-regulating genes) expression by in situ hybridisation (day 110) and immunohistochemistry (days 50, 65 and 110). At day 50, maternal nutrition had no effect on Ki67, predominant in germ cells, or Bax and Mcl-1, predominant in the oocytes. Restricted maternal food intake from 0 to 30 days significantly reduced staining for Ki67 in germ cells at day 65 ( P 0.05) but increased staining in granulosa cells at day 110 ( P 0.05). In animals fed the L ration for 110 days, primordial follicle Bax and Mcl-1 were significantly increased (Bax: P 0.01 Mcl-1: P 0.05). Granulosa cell Bax was also increased ( P 0.05). When the L ration was fed from 66 to 110 days, granulosa cell Bax ( P 0.05) and primordial follicle Mcl-1 ( P 0.01) were also significantly increased. In the fetal ovarian vasculature, animals underfed for 0–110 days had significantly elevated perivascular Mcl-1 ( P 0.001) and endothelial Bax expression ( P 0.05). Moreover, at day 110, endothelial Mcl-1 was increased by underfeeding from 0 to 30 days ( P 0.05). These data indicate that maternal undernutrition alters proliferation and the expression of apoptosis-regulating genes in the developing fetal ovary. The precise mechanism depends on the window of maternal food restriction.
Publisher: Springer Science and Business Media LLC
Date: 12-11-2018
Publisher: Elsevier BV
Date: 02-2018
Publisher: Oxford University Press (OUP)
Date: 12-2012
Abstract: Objective and issue-neutral qualitative assessments of livestock behavior could provide a powerful assessment of welfare, augmenting quantitative measures such as autonomic and endocrine changes, which are often difficult to assess under many commercial livestock conditions. We set out to validate the use of qualitative behavioral assessment (QBA) in sheep using controlled experimental conditions (transport as a challenge) and comparing assessments against physiological variables. The behavioral expression of 14 Merino wethers, which had never experienced land transport, were assessed during their first road event (naïve to transport), and then again on their seventh event, 8 d later (habituated to transport). Blood s les were collected immediately before loading and after unloading, and heart rate and core body temperature were measured continuously throughout each event. Continuous video footage recorded during each event was used to provide clips of in idual animals that were shown to observers for QBA. There was significant consensus (P < 0.001) amongst 63 observers in terms of their assessment of the behavioral expression of the sheep. Transport-naïve sheep were assessed as being more 'alert', 'anxious', and 'aware', whereas transport-habituated sheep were more 'comfortable', 'tired', and 'confident' (P = 0.015). Heart rate and heart rate variability, core body temperature and a stress leukogram were greater (P < 0.05) in sheep during the first (naïve) event compared with the habituated event, and were significantly correlated with the QBA scores (P < 0.05). In conclusion, QBA is a valid, practical and informative measure of behavioral responses to transport.
Publisher: Bioscientifica
Date: 03-1998
Abstract: Nutrition influences the reproductive axis via alteration of gonadotrophin secretion. However, a link between nutrition and the secretion of GnRH, which drives the axis, has yet to be established. The aim of the present study was to measure the change in the concentrations of metabolic substances in the cerebrospinal fluid of adult male sheep offered a diet designed to maintain constant gonadotrophin secretion (Group M n = 6), or a diet known to increase gonadotrophin secretion (Group M + L n = 6). On days 1, 3 and 10 of the dietary treatments, cerebrospinal fluid and jugular blood were s led and analysed for metabolic fuels (glucose, amino acids and free fatty acids) and metabolic hormones (insulin, insulin-like growth factor I, GH, prolactin, cortisol and the thyroid hormones). On day 11 of the dietary treatment, LH pulse frequency and mean FSH concentrations in Group M + L had increased relative to Group M and to day 0. Plasma concentrations of prolactin and insulin on days 3 and 10, and glucose and insulin-like growth factor I on day 10, were higher in Group M + L than in Group M, but only cerebrospinal fluid concentrations of insulin, glucose and certain amino acids were affected by the dietary treatments on days 3 and 10. Cerebrospinal fluid, but not plasma, concentrations of aspartate, tyrosine, cystine, phenylalanine and arginine on day 3, and glutamine, gamma-aminobutyric acid, threonine, alanine on days 3 and 10, were higher in Group M + L relative to Group M. On day 10, plasma and cerebrospinal fluid concentrations of arginine, phenylalaine, proline, tyrosine, methionine and phosphoserine, but only the plasma concentrations of linoleic acid, aspartate and serine, were higher in Group M + L than in Group M. Concentrations of triiodothyronine, thyroxine, and cortisol in plasma and cerebrospinal fluid were not affected. These results show that the nutritional stimulation of gonadotrophin secretion is accompanied primarily by fluctuations in plasma and cerebrospinal fluid concentrations of insulin and certain amino acids, which suggests that, when nutritional status is improved, insulin, amino acids and possibly glucose interact to modulate GnRH secretion.
Publisher: Elsevier BV
Date: 11-2018
Publisher: MDPI AG
Date: 18-06-2019
DOI: 10.3390/ANI9060368
Abstract: Flystrike is a major problem affecting sheep in Australia. Identification of ‘flystruck’ in iduals is crucial for treatment but requires labour-intensive physical examination. As the industry moves toward more low-input systems there is a need for remote methods to identify flystruck in iduals. The aim of this study was to investigate the behaviour of sheep with breech flystrike within a paddock setting. Video footage of sixteen Merino sheep eight later confirmed with flystrike and eight without was collected as they moved freely within the paddock with conspecifics. Quantitative behavioural measurements and a qualitative behavioural assessment (QBA) were conducted and compared to their breech conditions (i.e., faecal/urine staining flystrike severity). Both qualitative and quantitative assessments indicated behavioural differences between flystruck and non-flystruck animals. Flystruck sheep had a behavioural profile characterised by restless behaviour abnormal postures and reduced grazing time (p 0.05). Furthermore flystruck sheep were scored to have a more ‘exhausted/irritated’ demeanour using QBA (p 0.05). The behavioural responses also corresponded to the flystrike severity scores and condition of the breech area. We conclude that remotely assessed behaviour of flystruck sheep erges markedly from non-flystruck sheep and thus could be a low-input method for identifying and treating affected animals.
Publisher: Elsevier BV
Date: 09-2014
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/AN15076
Abstract: Rangeland goat bucks were used to evaluate the efficacy of a commercially available anti-gonadotrophin-releasing hormone vaccine, Improvac (Zoetis Australia, West Ryde, NSW, Australia). The hypothesis tested was that immunisation would suppress testosterone secretion by the testis and agonistic behaviour between male goats. We also compared intervals of 2 and 4 weeks between primary and booster immunisations and monitored responses over a 2-month period. The 45 goats were split into three groups (n = 15): one group receiving the vaccination booster on Day 14, one group receiving the vaccination booster on Day 28, and the Control group receiving sterile saline injections. Body mass, body condition score and scrotal circumference were measured fortnightly, and blood was collected at 2-week intervals and analysed for testosterone concentration. Behavioural interaction tests of 2-min duration were also conducted fortnightly. There was a significant decrease in paired testicular circumference (P 0.05) and testosterone concentration (P 0.01) in both vaccination groups by the end of the experiment at Day 60, compared with the Control group. Agonistic interactions measured at Day 60 were significantly reduced in both vaccination groups (P 0.05) compared with the Control group. These results support the efficacy of Improvac in reducing agonistic behaviours in rangeland goat bucks and suggest that the use of the vaccine may assist in reducing social stress and possible injury in groups of confined male goats.
Publisher: Elsevier BV
Date: 2013
Publisher: Oxford University Press (OUP)
Date: 23-04-2008
Publisher: Springer Science and Business Media LLC
Date: 18-10-2016
Publisher: Springer Science and Business Media LLC
Date: 31-10-2005
Abstract: The gut hormone, ghrelin, is involved in the neuroendocrine and metabolic responses to hunger. In monogastric species, circulating ghrelin levels show clear meal-related and body weight-related changes. The pattern of secretion and its role in ruminant species is less clear. Ghrelin acts via growth hormone secretagogue receptors (GHSR-1a) to alter food intake, fat utilization, and cellular proliferation. There is also evidence that ghrelin is involved in reproductive function. In the present study we used immunohistochemistry to investigate the presence of ghrelin and GHSR-1a in sheep reproductive tissues. In addition, we examined whether ghrelin and GHSR-1a protein expression is developmentally regulated in the adult and fetal ovine testis, and whether there is an association with markers of cellular proliferation, i.e. stem cell factor (SCF) and proliferating cell nuclear antigen (PCNA). Antibodies raised against ghrelin and its functional receptor, GHSR-type 1a, were used in standard immunohistochemical protocols on various reproductive tissues collected from adult and fetal sheep. GHSR-1a mRNA presence was also confirmed by in situ hybridisation. SCF and PCNA immunoexpression was investigated in fetal testicular s les. Adult and fetal testicular immunostaining for ghrelin, GHSR-1a, SCF and PCNA was analysed using computer-aided image analysis. Image analysis data were subjected to one-way ANOVA, with differences in immunostaining between time-points determined by Fisher's least significant difference. In adult sheep tissue, ghrelin and GHSR-1a immunostaining was detected in the stomach (abomasum), anterior pituitary gland, testis, ovary, and hypothalamic and hindbrain regions of the brain. In the adult testis, there was a significant effect of season (photoperiod) on the level of immunostaining for ghrelin (p 0.01) and GHSR-1a (p 0.05). In the fetal sheep testis, there was a significant effect of gestational age on the level of immunostaining for ghrelin (p 0.001), GHSR-1a (p 0.05), SCF (p 0.05) and PCNA (p 0.01). Evidence is presented for the presence of ghrelin and its receptor in various reproductive tissues of the adult and fetal sheep. In addition, the data indicate that testicular expression of ghrelin and its receptor is physiologically regulated in the adult and developmentally regulated in the fetus. Therefore, the ghrelin ligand/receptor system may have a role (endocrine and/or paracrine) in the development (cellular proliferation) and function of the reproductive axis of the sheep.
Publisher: Bioscientifica
Date: 05-1998
Abstract: The hypothalamo-pituitary-gonadal axis matures during fetal life and may be susceptible to adverse effects. Model systems can be used to understand its physiological role. The aim of this study was to determine whether antibodies to GnRH, administered to the mother, can cross the ovine fetal-placental barrier and suppress fetal gonadotrophin secretion. Maternal passive immunization to GnRH in pregnant Greyface ewes (day 103 of gestation) resulted in GnRH antibody titres of from 1:6000 to 1:9000 after 1 day and a suppression of the pulsatile secretion of fetal LH after 2 days. Fetal FSH concentrations declined gradually over the 11 days of the experiment and were only significantly different from control animals immunized against BSA in male fetuses. The slower decrease in fetal FSH concentrations than in LH concentrations shows that the secretion of FSH, unlike that of LH, is not dependent on short term changes in GnRH release. The lack of a suppressive effect of the maternal GnRH immunoneutralization on female fetal FSH secretion may be due to removal of the negative feedback effect of oestradiol and, possibly, inhibin. There was no sexual dimorphism in the effect of maternal GnRH immunoneutralization on fetal GnRH antibody titres or fetal LH secretion. These findings show that maternal passive immunization against GnRH results in GnRH antibodies crossing the fetal-placental barrier and suppressing fetal LH and FSH secretion in males, but only suppressing LH secretion in the females. Although the lack of effect on FSH secretion in the females needs to be investigated further, the present study provides evidence of a non-invasive procedure for blocking fetal gonadotrophin secretion which may be used to investigate hypothalamo-pituitary-gonadal function during early gestation in sheep.
Publisher: Elsevier BV
Date: 2010
Publisher: Bioscientifica
Date: 11-2002
Abstract: The role of leptin in neuroendocrine appetite and reproductive regulation remains to be fully resolved. A series of three experiments was conducted using adequately nourished oestradiol-implanted castrated male sheep. In a cross-over design (n=6), responses to a single i.c.v. (third ventricle) injection of leptin (0.5, 1.0 and 1.5 mg ovine leptin (oLEP) and 1.0 mg murine leptin (mLEP)), N-methyl-D-aspartate (NMDA, 20 micro g) or 0.9% saline (control) were measured in terms of LH secretion (4 h post-injection compared with 4 h pre-injection) and appetite (during 2 h post-injection) in autumn (Experiment 1). NMDA and 1.0 mg oLEP treatments were repeated in the same sheep in the following spring (Experiment 2). With an additional 12 sheep (n=18 in cross-over design), responses to low-dose 'physiological' i.c.v. infusion of leptin (8 ng/h for 12 h daily for 4 days), insulin (0.7 ng/h) and artificial cerebrospinal fluid were measured in the next spring (Experiment 3). LH was studied over 8 h and appetite over 1 h on days 1 and 4 of infusion. In Experiment 1 (autumn), oLEP overall increased LH pulse frequency by up to 110% (P .05), decreased LH pulse litude (P .05) and decreased appetite (P .05). mLEP reduced LH pulse litude (P .05) without significant effect on appetite, while NMDA reduced appetite (P .05) but had no effect on LH. In Experiment 2 (spring), LH responses were 'surge-like' with highly significant increases in the moving average LH concentration after 1.0 mg oLEP (P .001) and after NMDA (P .001). Compared with similar analysis of experiment 1 results, the LH response in spring was greater than that in autumn for both 1.0 mg oLEP (P .05) and NMDA (P .005). Conversely, unlike in autumn (Experiment 1), there was no effect of 1.0 mg oLEP or NMDA on appetite in the spring (Experiment 2). In Experiment 3 (spring), 'physiological' i.c.v. infusion of oLEP or insulin increased LH pulse frequency by up to 100% (P .001) compared with the control infusion on both days 1 and 4, but there were no effects on appetite. These results indicate that intracerebral leptin both stimulates reproductive neuroendocrine output and decreases appetite in adequately nourished sheep. However, the responses of these two axes were dose-dependent and differentially affected by the time of year, suggesting dissociation of the neural pathways involved.
Publisher: CSIRO Publishing
Date: 1996
DOI: 10.1071/AR9960843
Abstract: Supplementing mature rams with lupin seed (Lupinus angustifolius, a highly digestible source of energy and protein) increases gonadotrophin secretion within 5-10 days. When sheep receive a post-ruminal supplement of protein and energy equivalent to that in the lupin supplement, LH secretion is increased but not to the same extent as with lupin seed itself. This suggests that lupin seed contains a specific mixture of nutrients or an unknown component that exerts effects on the brain centres that control gonadotrophin secretion. This hypothesis was tested by comparing the responses to isonitrogenous and isoenergetic supplements of 3 legumes: lupins, cowpeas, and soybeans. Rams were fed the supplements for 10 days and blood was s led every 20 min for 24 h on days -1, 5, and 10 relative to the start of supplementation. The plasma was assayed for LH, FSH, and the metabolic hormones insulin and insulin-like growth factor 1 (IGF-1). Both the cowpea and the lupin supplements increased LH pulse frequency and the mean concentrations of insulin and IGF-1 on days 5 and 10 compared with day -1 (P 0.05). The soybean supplement did not affect LH pulse frequency or the concentrations of insulin or IGF-1. Only the cowpea supplement increased the mean concentration of FSH. The nutritional stimulation of the reproductive centres of the brain appears not to be specific to lupins, because the diet supplemented with cowpeas evoked similar responses. The lack of response to soybean seed suggests that the effects of diet on secretion of metabolic and gonadotrophic hormones are not due simply to the total energy and protein content of the diets, but to subtle differences in their chemical constituents.
Publisher: Springer Science and Business Media LLC
Date: 12-08-2019
Publisher: Bioscientifica
Date: 06-2002
Abstract: The aims of this study were to determine which hormones may have a role in the expression of maternal undernutrition effects on reproductive function, in both the developing fetus and the adult offspring. This was undertaken by measuring the effects of long-term maternal undernutrition on metabolic hormone profiles and pituitary responses to single doses of GnRH and GH-releasing factor (GRF) in fetal sheep. From mating, groups of ewes were fed rations providing either 100% (HIGH) or 50% (LOW) of estimated metabolisable energy requirements for pregnancy throughout the experiment until slaughter at approximately 119 days of gestation. Fetal and maternal blood s les were collected from 113 until 119 days of gestation, via carotid and jugular catheters respectively, and assayed for insulin, IGF-I, GH, thyroxine and triiodothyronine (T(3)). Undernutrition had no effects on fetal weight, fetal gonad weight of either sex, fetal insulin or IGF-I concentrations. Male LOW fetuses exhibited a significantly attenuated response (P .05) to a bolus challenge of GnRH compared with HIGH fetuses. Basal fetal GH concentrations and the response to exogenous GRF were similar in both treatment groups, although LOW fetuses exhibited more secretory episodes (P .01). Mean T(3) concentrations were significantly lower in both the maternal (P .01) and fetal (P .05) plasma of LOW animals compared with HIGH animals. It is concluded that pituitary function was altered in fetal males and could influence male reproductive development. On the other hand, in female sheep, fetal gonadal abnormalities and reductions in reproductive capacity in adult life which are associated with fetal undernutrition are unlikely to be attributable to altered pituitary function. Additionally, these studies raise the possibility that thyroid hormones may have a role in the expression of maternal undernutrition effects on fetal development.
Publisher: Elsevier BV
Date: 12-2012
Publisher: The Endocrine Society
Date: 11-2007
DOI: 10.1210/EN.2007-0534
Abstract: This study investigated how changing nutritional status may alter reproductive neuroendocrine (LH) output via circulating leptin and insulin signaling through orexigenic hypothalamic pathways. Thin sheep were given an increasing nutritional plane (INP), sheep with intermediate adiposity a static nutritional plane (SNP), and fat sheep a decreasing nutritional plane (DNP) for 6 wk. Mean group adiposities converged by wk 6, LH output increased in INP, remained unchanged in SNP, and decreased in DNP sheep. Plasma and cerebrospinal fluid (CSF) insulin and plasma leptin concentrations increased in INP but did not change in the SNP and DNP groups. In INP sheep, LH output correlated positively with adiposity and plasma and CSF insulin concentrations and negatively with orexigenic neuropeptide Y gene expression in the hypothalamic arcuate nucleus (ARC). In DNP sheep, LH output correlated positively with adiposity, CSF leptin concentrations, and ARC proopiomelanocortin gene expression and negatively with leptin receptor (OB-Rb) and agouti-related peptide gene expression in the ARC. These data are consistent with the feedback response to an increasing nutritional plane being mediated by increasing circulating insulin entering the brain and stimulating LH via inhibition of hypothalamic neuropeptide Y and the response to a decreasing nutritional plane being mediated by altered hypothalamic leptin signaling brought about by increased OB-Rb expression and decreased melanocortin signaling. Because end point adiposity was similar yet LH output was different, the hypothalamus apparently retains a nutritional memory, based on changes in orexigenic neuropeptide expression, that influences contemporary neuroendocrine responses.
Publisher: CSIRO Publishing
Date: 2011
DOI: 10.1071/RD10150
Abstract: Long-term nutritional background is thought to influence hypothalamic appetite and reproductive neuroendocrine responses to short-term nutritional feedback. In order to investigate this phenomenon, the effects of intracerebroventricular administration of insulin or neuropeptide-Y (NPY) on LH secretion and voluntary food intake (VFI) were examined in sheep that were initially thin and kept on an increasing nutritional plane (INP), or initially fat and kept on a decreasing nutritional plane (DNP), for 10 weeks. Intracerebroventricular insulin stimulated LH secretion and suppressed VFI in INP sheep when initially thin, but not when they became fat, and had no effect on LH in DNP sheep when initially fat, and stimulated LH secretion when they became thin. Intracerebroventricular NPY had no effect on LH or VFI in INP sheep when initially thin, decreased LH secretion and increased VFI when they became fat, and decreased LH secretion in DNP sheep when initially fat but had no effect when they became thin. Therefore, sensitivity to insulin increases with low or decreasing nutritional status and decreases with high or increasing nutritional status, whereas sensitivity to NPY increases with high or increasing nutritional status and decreases with low or decreasing nutritional status. In conclusion, reproductive neuroendocrine and appetite responses to acute changes in nutritional feedback signals depend on the in idual’s longer-term nutritional background.
No related grants have been discovered for David Miller.