ORCID Profile
0000-0003-1783-1049
Current Organisation
New South Wales Department of Primary Industries
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Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/AN17141
Abstract: Ruminant livestock contribute to atmospheric methane (CH4) from enteric microbial fermentation of feed in the reticulo-rumen. Our research aimed to increase understanding of how digestive characteristics and rumen anatomy of the host animal contribute to variation in CH4 emissions between in idual sheep. In total, 64 ewes were used in an incomplete block experiment with four experimental test periods (blocks). Ewes were chosen to represent the ersity of phenotypic variation in CH4 emissions: there were at least 10 offspring from each of four sires and a range of liveweights. Throughout the experiment, the ewes were fed equal parts of lucerne and oaten chaff, twice daily, at 1.5 times the maintenance requirements. Daily CH4 emission (g/day) increased significantly (P & 0.001) with an increasing dry-matter intake (DMI) and reticulo-rumen volume (P & 0.001). Lower methane yield (g CH4/kg DMI) was associated with shorter mean retention times of liquid (r = 0.59 P & 0.05) and particle (r = 0.63 P & 0.05) phases of the digesta in the rumen. Significant between sire variation was observed in CH4 emissions and in rumen volume (P = 0.02), the masses of liquids (P = 0.009) and particles (P & 0.03) in the rumen and the proportion of gas in the dorsal sac of the rumen (P = 0.008). The best predictors of variation in CH4 emissions due to the host were DMI, CO2 emissions, rumen volume, liveweight, mean retention time of particles in the rumen, dorsal papillae density and the proportion of liquid in the contents of the rumen compartments.
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/EA02220
Abstract: There is a growing body of evidence that there is genetic variation in beef cattle feed intake relative to their liveweight and weight gain. Difference in feed intake, above and below that expected or predicted on the basis of size and growth, is measured as residual feed intake. Variation in residual feed intake must be underpinned by measurable differences in biological processes. This paper summarises some plausible mechanisms by which variation in efficiency of nutrient use may occur and presents several testable hypotheses for such variation. A� companion paper [Richardson and Herd (2004) Aust. J. Exp. Ag. 44, 431–441] presents results from experiments on cattle following ergent selection for residual feed intake. There were at least 5 major processes identified by which variation in efficiency can arise. These are associated with variation in intake of feed, digestion of feed, metabolism (anabolism and catabolism associated with and including variation in body composition), activity and thermoregulation. The percentage contribution of different mechanisms, to variation in residual feed intake, was: 9% for differences in heat increment of feeding 14% for differences in digestion 5% for differences in body composition and 5% for differences in activity. Together, these mechanisms may be responsible for about one-third of the variation in residual feed intake. The remaining two-thirds were likely to be associated with heat loss due to variation in other processes, such as protein turnover and ion transport. There is no shortage of candidate mechanisms that, singularly or in combination, might contribute to genetic variation in energy utilisation in ruminants. Further research in beef cattle, to better define these mechanisms and enable their incorporation into breeding programmes, may lead not only to cattle which eat less for the same performance, but are superior in other traits as well.
Publisher: Elsevier BV
Date: 2014
Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/AN17447
Abstract: Livestock produce 10% of the total CO2-equivalent greenhouse gases in Australia, predominantly as methane from rumen fermentation. Genetic selection has the potential to reduce emissions and be adopted in Australian grazing systems. Developing a breeding objective for reduced methane emissions requires information about heritability, genetic relationships, when best to measure the trait and knowledge of the annual production of methane. Among- and within-animal variation in methane production, methane yield and associated traits were investigated, so as to determine the optimal time of measurement and the relationship between that measurement and the total production of methane. The present study measured 96 ewes for methane production, liveweight, feed intake, rumen volume and components, and volatile fatty acid (VFA) production and composition. Measurements were recorded at three ages and different physiological states, including growing (12 months), dry and pregnant (21 months) and dry (non-pregnant, non-lactating 28 months of age). The single biggest determinant of methane production was feed intake, but there were additional effects of age, proportion of propionate to (acetate+butyrate) in rumen VFA, total VFA concentration and CO2 flux. Rumen volume and pregnancy status also significantly affected methane production. Methane production, CO2 flux, liveweight, feed intake and rumen volume had high repeatability (& %), but repeatability of methane yield and VFA traits were low (& %). There were no interactions between sire and age (or pregnancy status) for methane traits. This suggests that methane could be measured at any time in the production cycle. However, because MY is reduced during pregnancy, it might be best to measure methane traits in dry ewes (neither pregnant nor lactating).
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/AN14874
Abstract: The overall efficiency of beef production is considered more highly correlated with cow–calf efficiency, viz. maternal productivity (MP), than the efficiency of other segments of the beef production chain. Recently, concerns have been raised that improvements in feedlot and carcass performance have led to a decline in MP due to the uncertainty that surrounds the relationships between production and MP traits. The Beef Cooperative Research Centre ‘Maternal Productivity’ Project examined the impact of cow genotype and nutrient intake on breeding herd productivity. This experiment demonstrated that cow body composition is influenced by genetic differences in rib fat and residual feed intake, as well as nutrient availability. Genetic differences in rib fat were shown to influence heifer pregnancy rates, observed days to calving, MP when nutrient intake is restricted and ME intake by the cow–calf unit. Weaning rate was found to account for a large portion of the variation in MP, while cow genetic background and pre-weaning nutrient availability influenced the postweaning and carcass performance of progeny. These findings demonstrate that although balancing the requirements of MP with those of other traits is not straight forward, it is of critical importance. Incorporating modelling systems into decision-support systems (DSS) offers the opportunity to integrate fragmented knowledge into decision making. Unfortunately, previous DSS have gained little traction and limited adoption due to their perceived complexity, large input-data requirements, and mismatches between outputs and the decision-making styles of producers. The development of the BeefSpecs fat calculator provides an ex le of how producer-measurable inputs and simple user interactions can be combined using modelling systems to develop DSS to improve MP. No single model that addressed all issues affecting MP was found in the literature. Thus, it was concluded that previous modelling systems would need to be combined to develop a suite of DSS that target-specific components of MP, such as heifer pregnancy rates and interactions between the cow herd and the nutritional environment.
Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/AN19229
Abstract: Increased market pressure to improve meat yield and quality require improved methods of predicting body composition in growing animals. Current systems of animal nutrition based on nutrient supply and animal characteristics predict animal growth from nutrient inputs, but, as of yet, do not accurately predict body composition. The present paper explores the evidence and data required to support an existing model of the effects of energy intake on visceral and muscle protein mass and energy expenditure to predict heat production, growth and body composition of sheep. While parameters of the model related to energetic costs of protein in muscle and viscera can be supported by independent studies, parameters associated with energetic costs of protein gain, particularly in viscera, are harder to reconcile with independent measurements. The range of available data on systematic changes in visceral organ mass over time in response to feed intake is limited, which may constrain generalisation of the parameters of the model with regard to the wide range of production situations faced by the sheep and cattle industries. However, sufficient data exist in the literature to test, and if required, revise the current framework.
Publisher: Springer Science and Business Media LLC
Date: 08-11-2007
Publisher: Springer Science and Business Media LLC
Date: 12-2011
Abstract: In livestock populations the genetic contribution to muscling is intensively monitored in the progeny of industry sires and used as a tool in selective breeding programs. The genes and pathways conferring this genetic merit are largely undefined. Genetic variation within a population has potential, amongst other mechanisms, to alter gene expression via cis- or trans-acting mechanisms in a manner that impacts the functional activities of specific pathways that contribute to muscling traits. By integrating sire-based genetic merit information for a muscling trait with progeny-based gene expression data we directly tested the hypothesis that there is genetic structure in the gene expression program in ovine skeletal muscle. The genetic performance of six sires for a well defined muscling trait, longissimus lumborum muscle depth, was measured using extensive progeny testing and expressed as an Estimated Breeding Value by comparison with contemporary sires. Microarray gene expression data were obtained for longissimus lumborum s les taken from forty progeny of the six sires (4-8 progeny/sire). Initial unsupervised hierarchical clustering analysis revealed strong genetic architecture to the gene expression data, which also discriminated the sire-based Estimated Breeding Value for the trait. An integrated systems biology approach was then used to identify the major functional pathways contributing to the genetics of enhanced muscling by using both Estimated Breeding Value weighted gene co-expression network analysis and a differential gene co-expression network analysis. The modules of genes revealed by these analyses were enriched for a number of functional terms summarised as muscle sarcomere organisation and development, protein catabolism (proteosome), RNA processing, mitochondrial function and transcriptional regulation. This study has revealed strong genetic structure in the gene expression program within ovine longissimus lumborum muscle. The balance between muscle protein synthesis, at the levels of both transcription and translation control, and protein catabolism mediated by regulated proteolysis is likely to be the primary determinant of the genetic merit for the muscling trait in this sheep population. There is also evidence that high genetic merit for muscling is associated with a fibre type shift toward fast glycolytic fibres. This study provides insight into mechanisms, presumably subject to strong artificial selection, that underpin enhanced muscling in sheep populations.
Publisher: Oxford University Press (OUP)
Date: 10-2015
Abstract: Emissions of 710 ewes at pasture were measured for 1 h (between 09:00-16:30 h) in batches of 15 sheep in portable accumulation chambers (PAC) after an overnight fast continuing until 2 h before measurement, when the sheep had access to baled hay for 1 h. The test was used to identify a group of 104 low emitters (I-Low) and a group of 103 high emitters (I-Hi) for methane emissions adjusted for liveweight (CHawt). The 207 ewes selected at the initial study were remeasured in 5 repeat tests from 2009 through 2014 at another location. The first repeat used the original measurement protocol. Two modified protocols, each used in 2 yr, drafted unfasted sheep on the morning of the test into a yard or holding paddock until measurement. Emissions of the I-Hi sheep were higher (102-112%) than I-Low sheep in all subsequent PAC tests, with statistical significance ( < 0.05) in 3 tests. Tests without overnight fasting were simpler to conduct and had repeatabilities of 51 to 60% compared with 31 and 43% for the initial and first repeat tests, respectively. After habituation to a diet fed at 20 g/kg liveweight, 160 of the 207 sheep were measured in respiration chambers (RC) 10 high (Hi-10) and 10 low (Low-10) sheep were chosen, representing extremes (top and bottom 6.25%) for methane yield (MY g CH/kg DMI). The Hi-10 group emitted 14% more methane (adjusted for feed intake) in a follow-up RC test, but Low-10 and Hi-10 sheep differed in only 1 of the 5 PAC tests, when Hi-10 sheep emitted less CHawt than Low-10 sheep ( = 0.002) and tended to eat less in the feeding opportunity ( = 0.085). Compared with their weight on good pasture, Low-10 sheep were proportionately lighter than Hi-10 sheep in the relatively poor pasture conditions of the initial test. Sheep identified as low emitters by PAC tests using the initial protocol did not produce less CH (mg/min) when fed a fixed level of intake in RC. Correlations between estimates of an animal's CHawt measured in PAC and CH adjusted for feed intake in RC were quite low ( = 0-19%) and significant ( < 0.05) in only 1 test of unfasted sheep. With moderate repeatability over the 5 yr, PAC tests of CHawt could be a viable way to select for reduced emissions of grazing sheep. As well as exploiting any variation in MY, selecting for reduced CHawt in PAC could result in lower feed intake than expected for the animals' liveweight and might affect the diurnal feeding pattern. Further work is required on these issues.
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/AN15365
Abstract: The methods for estimating methane emissions from cattle as used in the Australian national inventory are based on older data that have now been superseded by a large amount of more recent data. Recent data suggested that the current inventory emissions estimates can be improved. To address this issue, a total of 1034 in idual animal records of daily methane production (MP) was used to reassess the relationship between MP and each of dry matter intake (DMI) and gross energy intake (GEI). Data were restricted to trials conducted in the past 10 years using open-circuit respiration chambers, with cattle fed forage-based diets (forage %). Results from diets considered to inhibit methanogenesis were omitted from the dataset. Records were obtained from dairy cattle fed temperate forages (220 records), beef cattle fed temperate forages (680 records) and beef cattle fed tropical forages (133 records). Relationships were very similar for all three production categories and single relationships for MP on a DMI or GEI basis were proposed for national inventory purposes. These relationships were MP (g/day) = 20.7 (±0.28) × DMI (kg/day) (R2 = 0.92, P 0.001) and MP (MJ/day) = 0.063 (±0.008) × GEI (MJ/day) (R2 = 0.93, P 0.001). If the revised MP (g/day) approach is used to calculate Australia’s national inventory, it will reduce estimates of emissions of forage-fed cattle by 24%. Assuming a global warming potential of 25 for methane, this represents a 12.6 Mt CO2-e reduction in calculated annual emissions from Australian cattle.
Publisher: Oxford University Press (OUP)
Date: 10-2014
Abstract: A total of 2,600 methane (CH4) and 1,847 CO2 measurements of sheep housed for 1 h in portable accumulation chambers (PAC) were recorded at 5 sites from the Australian Sheep CRC Information Nucleus, which was set up to test leading young industry sires for an extensive range of current and novel production traits. The final validated dataset had 2,455 methane records from 2,279 animals, which were the progeny of 187 sires and 1,653 dams with 7,690 animals in the pedigree file. The protocol involved rounding up animals from pasture into a holding paddock before the first measurement on each day and then measuring in groups of up to 16 sheep over the course of the day. Methane emissions declined linearly (with different slopes for each site) with time since the sheep were drafted into the holding area. After log transformation, estimated repeatability (rpt) and heritability (h(2)) of liveweight-adjusted CH4 emissions averaged 25% and 11.7%, respectively, for a single 1-h measurement. Sire × site interactions were small and nonsignificant. Correlations between EBV for methane emissions and Sheep Genetics Australia EBV for production traits were used as approximations to genetic correlations. Apart from small positive correlations with weaning and yearling weights (r = 0.21-0.25, P < 0.05), there were no significant relationships between production trait and methane EBV (calculated from a model adjusting for liveweight by fitting separate slopes for each site). To improve accuracy, future protocols should use the mean of 2 (rpt = 39%, h(2) = 18.6%) or 3 (rpt = 48%, h(2) = 23.2%) PAC measurements. Repeat tests under different pasture conditions and time of year should also be considered, as well as protocols measuring animals directly off pasture instead of rounding them up in the morning. Reducing the time in the PAC from 1 h to 40 min would have a relatively small effect on overall accuracy and partly offset the additional time needed for more tests per animal. Field testing in PAC has the potential to provide accurate comparisons of animal and site methane emissions, with potentially lower cost/increased accuracy compared to alternatives such as SF6 tracers or open path lasers. If similar results are obtained from tests with different protocols/seasonal conditions, use of PAC measurements in a multitrait selection index with production traits could potentially reduce methane emissions from Australian sheep for the same production level.
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.MEATSCI.2013.03.029
Abstract: This study evaluated the effects of the myostatin g+6723G>A mutation on carcass and meat quality traits of lamb (AA: n=5 AG: n=8 GG: n=9). Dressing percentage was positively affected by the mutation with homozygotes for the mutation having the highest yield. Regarding carcass composition, there was a significant increase in the proportional weights of the loin and hindquarter muscles. Objective meat quality traits of the M. longissimus lumborum (LL) and M. semimembranosus (SM) were not significantly affected. For the SM, toughness (shear force and compression) tended to be lowest for homozygotes for the mutation. The myostatin g+6723G>A mutation did not affect sensory meat quality traits of grilled steaks for the LL, but resulted in a significant improvement in eating quality for the SM. Given the number of animals in this study, the robustness of the outcome of this study with regard to the effects on meat quality and its causes requires further investigation.
Publisher: Oxford University Press (OUP)
Date: 10-2016
Abstract: Feed intake (FI), live weight (LW), and ADG were recorded over 31 d in ninety-six 12-month-old ewes (progeny of 4 sires) given ad libitum access to chaffed lucerne/cereal hay. Methane (CH) and CO emissions of each ewe were measured for 40 to 60 min in portable accumulation chambers (PAC) and in respiration chambers (RC) over 22 h. Testing in RC increased the variability of FI on the test day and depressed the amount eaten from an average of 1,384 to 1,062 g/d FI depression increased by 0.63 ± 0.24 percentage points for every kilogram of additional LW. Repeatabilities of PAC measurements were 0.76 (CH) and 0.81 (CO). After adjusting for LW and ADG, repeatabilities were 0.47 (PAC CH) and 0.43 (PAC CO). Daily FI measurements had similar repeatability (0.76 before and 0.42 after adjustment for LW and ADG). The PAC measurements were highly correlated with mean 31-d FI ( = 0.81 for both CH and CO). After adjustment for LW and ADG, PAC measurements were moderately correlated with residual feed intake (RFI = 0.37 for CH, 0.31 for CO). The CH:CO ratio was also significantly correlated with mean 31-d FI ( = 0.52). After most of the ewes had given birth and raised lambs, repeat PAC measurements were available for 91 of the ewes at 2 years of age (with ad libitum access to the same feed). Correlations with the 2012 PAC measurements were 0.64 (CH) and 0.75 (CO). After adjusting 2014 PAC measurements for LW, correlations with RFI in 2012 were 0.34 (CH) and 0.33 (CO), with a clear relationship between sire means for RFI in 2012 and PAC CH adjusted for LW in 2014. These results suggest that PAC tests under similar feeding conditions are repeatable over an extended time period and can provide useful information on FI and feed efficiency as well as methane emissions. Analyses of RC measurements might need to consider FI depression.
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/EA07231
Abstract: Rates of whole-body protein turnover and energy expenditure were measured in two groups of wethers differing in estimated breeding values (EBVs) for wool growth, but with similar EBVs for fibre diameter and liveweight (LW). The sheep were offered a pelleted diet at 1.2 times their metabolisable energy (ME) requirement for maintenance (1.2 M) followed by either 0.8 M or 1.8 M for 5 weeks. In the 5th week, whole-body protein metabolism was estimated by using intravenous injection of 15N-glycine (g N/day) and whole-body energy expenditure rate (EE) was predicted by the CO2 entry rate technique using intravenous injection of NaH13CO3. The higher N intake (8.7 v. 20.4 g N/day, P 0.001) was associated with a higher whole-body protein flux (22.1 v. 34.2 g N/day, P 0.001), and a higher whole-body protein synthesis rate (17.0 v. 25.5 g N/day, P 0.001) and protein degradation rate (15.9 v. 20.7 g N/day, P 0.001). Irrespective of feeding levels, sheep with high-fleece EBVs (F+) synthesised and degraded more body protein N (g N/day) than sheep with low-fleece EBVs (F–), and F+ sheep also retained more ingested protein N (P 0.05) in wool and body tissue than F– sheep, but the significant differences due to genotypes disappeared when whole-body protein flux, synthesis and degradation were expressed as g N/kg LW0.75.day (metabolic weight). Estimates of EE were lower when the sheep were offered 0.8 M than when offered 1.8 M (5.85 v. 7.68 MJ/day, P 0.001) and were higher in F+ than in F– sheep (6.95 v. 6.58 MJ/day P 0.05), but F+ sheep had a significantly lower (P 0.05) EE (MJ/kg LW0.75.day) than F– sheep. F+ animals also retained more energy in wool and wool-free body tissue than F– animals (P 0.05). The present study indicates that genetic selection for wool growth has resulted in increased efficiency of dietary protein and energy use for wool production and body-tissue growth in these sheep. Furthermore, there is no ‘trade off’ between deposition of nutrients in the body and wool in sheep with high EBVs for wool growth.
Publisher: CSIRO Publishing
Date: 10-03-2022
DOI: 10.1071/AN21270
Abstract: Context Genotype by environment interaction or sire re-ranking between measurements of methane emission in different environments or from using different measurement protocols can affect the efficiency of selection strategies to abate methane emission. Aim This study tested the hypothesis that measurements of methane emission from grazing sheep under field conditions, where the feed intake is unknown, are genetically correlated to measurements in a controlled environment where feed intake is known. Methods Data on emission of methane and carbon dioxide and uptake of oxygen were measured using portable accumulation chambers from 499 animals in a controlled environment in New South Wales and 1382 animals in a grazing environment in Western Australia were analysed. Genetic linkage between both environments was provided by 140 sires with progeny in both environments. Multi-variate animal models were used to estimate genetic parameters for the three gas traits corrected for liveweight. Genetic groups were fitted in the models to account for breed differences. Genetic correlations between the field and controlled environments for the three traits were estimated using bivariate models. Key results Animals in the controlled environment had higher methane emission compared to the animals in the field environment (37.0 ± s.d 9.3 and 35.3 ± s.d 9.4 for two protocols vs 12.9 ± s.d 5.1 and 14.6 ± s.d 4.8 mL/min for lambs and ewes (±s.d) P 0.05) but carbon dioxide emission and oxygen uptake did not significantly differ. The heritability estimates for methane emission, carbon dioxide emission and oxygen uptake were 0.15, 0.06 and 0.11 for the controlled environment and 0.17, 0.27 and 0.35 for the field environment. The repeatability for the traits in the controlled environment ranged from 0.51 to 0.59 and from 0.24 to 0.38 in the field environment. Genetic correlations were high (0.85–0.99) but with high standard errors. Conclusion Methane emission phenotypes measured using portable accumulation chambers in grazing sheep can be used in genetic evaluation to estimate breeding values for genetic improvement of emission related traits. The combined measurement protocol-environment did not lead to re-ranking of sires. Implication These results suggest that both phenotypes could be used in selection for reduced methane emission in grazing sheep. However, this needs to be consolidated using a larger number of animals and sires with larger progeny groups in different environments.
Publisher: Oxford University Press (OUP)
Date: 09-2016
Abstract: Estimates of genetic henotypic covariances and economic values for slaughter weight, growth, feed intake and efficiency, and three potential methane traits were compiled to explore the effect of incorporating methane measurements in breeding objectives for cattle and meat sheep. The cost of methane emissions was assumed to be zero (scenario A), A$476/t (based on A$14/t CO equivalent and methane's 100-yr global warming potential [GWP] of 34 scenario B), or A$2,580/t (A$30/t CO equivalent combined with methane's 20-yr GWP of 86 scenario C). Methane traits were methane yield (MY methane production ided by feed intake based on measurements over 1 d in respiration chambers) or short-term measurements of methane production adjusted for live weight (MPadjWt) in grazing animals, e.g., 40-60 min measurements in portable accumulation chambers (PAC) on 1 or 3 occasions, or measurements for 1 wk using a GreenFeed Emissions Monitor (GEM) on 1 or 3 occasions. Feed costs included the cost of maintaining the breeding herd and growth from weaning to slaughter. Sheep were assumed to be grown and finished on pasture (A$50/t DM). Feed costs for cattle included 365 d on pasture for the breeding herd and averages of 200 d postweaning grow-out on pasture and 100 d feedlot finishing. The greatest benefit of including methane in the breeding objective for both sheep and cattle was as a proxy for feed intake. For cattle, 3 GEM measurements were estimated to increase profit from 1 round of selection in scenario A (no payment for methane) by A$6.24/animal (from A$20.69 to A$26.93) because of reduced feed costs relative to gains in slaughter weight and by A$7.16 and A$12.09/animal, respectively, for scenarios B and C, which have payments for reduced methane emissions. For sheep, the improvements were more modest. Returns from 1 round of selection (no methane measurements) were A$5.06 (scenario A), A$4.85 (scenario B), and A$3.89 (scenario C) compared to A$5.26 (scenario A), A$5.12 (scenario B), and A$4.72 (scenario C) for 1 round of selection with 3 PAC measurements. Including MY in the selection index was less profitable because it did not reduce feed costs relative to weight gain. Consequently, for strategies measuring MY but not MPadjWt (and with no estimate of feed intake in the production environment), proportionately greater emphasis was placed on increasing slaughter weight, and as a result, the decreases in methane emissions per animal and per unit of feed intake were smaller than for strategies that measured MPadjWt.
Publisher: CSIRO Publishing
Date: 2001
DOI: 10.1071/EA00029
Abstract: The intrinsic properties (those extant at the time of slaughter) of bovine skeletal muscle as they relate to the subsequent quality attributes of beef are reviewed here. Attributes of bovine skeletal muscle that ultimately affect toughness, colour, fat content, flavour, juiciness, and nutritive value of beef are discussed. The dynamic nature of muscle development, particularly with regard to structure and composition, is highlighted. Variation in development of muscle structure and composition due to inherited (genetic) factors and environment (particularly nutrient supply) are described. Ex les are given of the implications of sources of variation due to animal genotype, age, nutrient supply, and hormonal environment on muscle cellularity and growth, fibre type, connective tissue composition and structure as they affect meat quality attributes. Key intrinsic properties of muscle include muscle type, cellularity, size, myofibre type, connective tissue composition and structure, glycogen and fat content and proteolytic activity. Activity of the calpain system at slaughter is seen as an important attribute. Regulation of myofibrillar and connective tissue proteolysis in vivo are discussed together with implications for subsequent meat quality. Amongst the on-farm environmental factors, nutritional history and developmental pathway are identified as factors that can be responsible for significant variation in the intrinsic properties of muscle that contribute to variation in toughness, colour and fat content, and thus consumer liking of beef.
Publisher: CSIRO Publishing
Date: 17-04-2009
DOI: 10.1071/AN20664
Abstract: Context Mice bred to be genetically different in feed efficiency were used in this experiment designed to help improve our knowledge of the biological basis of variation in feed efficiency between in idual animals. Aims This experiment used mice to explore the metabolic basis of genetic variation in feed efficiency in the growing animal. Methods Mice bred to differ in residual feed intake (RFI) recorded over a postweaning test were used. After 11 generations of ergent selection, mice in groups were tested for RFI from 6 to 8, 8 to 10, and 10 to 12 weeks of age, and measured for traits describing the ability to digest feed, body composition, protein turnover, basal and resting metabolic rate, and level of activity. Key results Compared with the low-RFI (high efficiency) line mice, high-RFI mice consumed 28% more feed per day over their RFI-test, were no heavier, were leaner (16% less total fat per unit of bodyweight), did not differ in the fractional synthesis rate of protein in skeletal muscle or in liver, and had similar basal metabolic rates at 33°C. On an energy basis, the selection lines did not differ in energy retained in body tissue gain, which represented only 1.8% of metabolisable energy intake. The remaining 98.2% was lost as heat. Of the processes measured contributing to the higher feed intake by the high-RFI mice, 47% of the extra feed consumed was lost in faeces and urine, activity was 84% higher and accounted for 24%, the cost of protein gain was 6% higher and accounted for 2%, and the energy cost of digesting and absorbing the extra feed consumed and basal heat production could have accounted for 11 and 15% each. Conclusions Selection for low RFI (high efficiency) in mice was accompanied by an increase in body fat, an improvement in the process of digestion, a lower rate of protein turnover and a much lower level of activity. Selection did not result in major change in basal metabolic rate. Implications This experiment with mice provided new information on the biological basis of genetic differences in feed efficiency. The experiment investigated the relative importance of major energy-consuming metabolic processes and was able to quantify the responses in protein turnover and level of activity, being responses in energy-consuming processes that have proven difficult to quantitatively demonstrate in large farm animals.
Publisher: Oxford University Press (OUP)
Date: 04-2017
Abstract: The objective of this study was to develop a proof of concept for using off-the-shelf Red Green Blue-Depth (RGB-D) Microsoft Kinect cameras to objectively assess P8 rump fat (P8 fat mm) and muscle score (MS) traits in Angus cows and steers. Data from low and high muscled cattle (156 cows and 79 steers) were collected at multiple locations and time points. The following steps were required for the 3-dimensional (3D) image data and subsequent machine learning techniques to learn the traits: 1) reduce the high dimensionality of the point cloud data by extracting features from the input signals to produce a compact and representative feature vector, 2) perform global optimization of the signatures using machine learning algorithms and a parallel genetic algorithm, and 3) train a sensor model using regression-supervised learning techniques on the ultrasound P8 fat and the classified learning techniques for the assessed MS for each animal in the data set. The correlation of estimating hip height (cm) between visually measured and assessed 3D data from RGB-D cameras on cows and steers was 0.75 and 0.90, respectively. The supervised machine learning and global optimization approach correctly classified MS (mean [SD]) 80 (4.7) and 83% [6.6%] for cows and steers, respectively. Kappa tests of MS were 0.74 and 0.79 in cows and steers, respectively, indicating substantial agreement between visual assessment and the learning approaches of RGB-D camera images. A stratified 10-fold cross-validation for P8 fat did not find any differences in the mean bias ( = 0.62 and = 0.42 for cows and steers, respectively). The root mean square error of P8 fat was 1.54 and 1.00 mm for cows and steers, respectively. Additional data is required to strengthen the capacity of machine learning to estimate measured P8 fat and assessed MS. Data sets for and continental cattle are also required to broaden the use of 3D cameras to assess cattle. The results demonstrate the importance of capturing curvature as a form of representing body shape. A data-driven model from shape to trait has established a proof of concept using optimized machine learning techniques to assess P8 fat and MS in Angus cows and steers.
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/AN18383
Abstract: Context Knowledge of genetic and phenotypic variation and the accuracy of different measurement techniques is needed to successfully reduce livestock methane (CH4) emissions. Aims To estimate repeatabilities, heritabilities and genetic correlations of respiration-chamber (RC) and portable accumulation-chamber (PAC) measurements using two different protocols but the same management and feeding conditions. Methods Australian Information Nucleus Flock ewes were measured in seven test-batches. The 510 ewes were removed from pasture and habituated to chaffed alfalfa and cereal hay at 1.5–1.6 times maintenance. Methane was measured in RC for two 22-h periods approximately 14 days apart, and 40 min in PAC, either immediately after removal from in idual pens (with feed as described above, PAC0), or 1-h after withdrawing feed (PAC1). There were up to 48 PAC0 tests per day (at 0930 hours, 1100 hours, 1230 hours, 1400 hours in 12 PAC) and 24 PAC1 tests per day (at 1100 hours and 1300 hours). Test methods (RC, PAC0, PAC1) were analysed as different traits in a multi-trait repeated-measures model. Key results Before adjustment for liveweight (Lwt) or feed intake (FI), CH4 was highly repeatable (RC 78%, PAC0 83%, PAC1 82%), with heritabilities of 39–55%, permanent environmental (PE) animal variances 23–43% of phenotypic variances (Vp), high genetic correlations between methods (98–100%), and lower PE correlations (44–58%). A second PAC test on the same day decreased CH4 by 8–12% compared with the ewe’s first test that day. Heritabilities of FI from 0800 hours until the test was complete (FIOD) were 16–17% (PAC) and 25% (RC) before adjusting for Lwt, with high PE variances (PAC 67–73%, RC 41% of Vp). FI in the previous 24 h was highly heritable and much less variable than was FIOD in the RC, suggesting that testing introduced additional variation by disrupting feeding patterns. After adjusting CH4 for Lwt, FIOD and FI in the previous 24 h and Lwt, some additive genetic variation remained, averaging 17% of Vp. Multivariate models of CH4 and FI, fitting a single animal term (representing genetic+PE variation) showed high animal correlations between FI and CH4, namely, 90–95% before, and 86–95% after adjusting for Lwt. Conclusions PAC measurements are heritable and highly correlated with RC measurements under similar management conditions. The high genetic and animal correlations of PAC CH4 and FI imply that CH4 is a useful proxy for FI of grazing animals.
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/AN13370
Abstract: This study was designed to screen a large number of sheep to identify in iduals with high and low methane (CH4) production, and to estimate repeatability and heritability of CH4 emissions in sheep, utilising portable accumulation chambers (PAC) designed for in-field use. Mature ewes (n = 710) selected from a research flock with known sires had their CH4 production over 1 h measured in PAC [CH4 (g1h)]. In iduals with High (n = 103) or Low (n = 104) CH4 (g1h), adjusted for liveweight (LW), were selected and re-measured on three occasions 1–4 months later, at another site with more abundant and better quality pasture. Mean of the selected (207) ewes CH4 (g1h) emissions were ~50% higher than at the first measurement site (0.66 g vs 0.42 g). LW was a significant correlate of CH4 production (r = 0.47). Correlations between CH4 (g1h) for the three PAC measurements at Site 2, before adjusting for LW ranged from 0.44 to 0.55. After adjusting for the effect of LW, repeatability was 0.33 at the first and 0.43 at the second site. The correlation between estimates of an animal’s emissions at the first and second sites, adjusted for LW, was 0.24. Initial CH4 production of the selected High group was 32% greater than the Low group (P 0.0001). On re-measurement there was still a significant difference (9–15%, P 0.006) between Low and High groups. The initial estimate of heritability of CH4 (g1h), based on variation between the ewes’ sires (0.13), was not maintained across the two sites. This may be due to genotype × environment interactions. We postulate that aspects of rumen physiology, which modulate CH4 production, could be expressed differently in different nutritional environments. Our results indicate that field use of PAC to screen sheep populations for CH4 production is both robust and repeatable. However, further investigations are required into the relationship between CH4 output of in idual animals in PAC compared with the more controlled conditions in respiration chambers.
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/AR02085
Abstract: A total of 7622 cattle were measured for several weight and body composition traits in temperate and tropically adapted breeds. Traits included: liveweight, hip height, body fat score, muscle score, flight time, ultrasound scanned fatness, and eye muscle area. Measurements were taken at 3 stages during the project: post-weaning, start of finishing, and end of finishing (i.e. pre-slaughter). Animals were finished to 3 target market-weight end-points (220, 280, or 340 kg carcass weight), either on pasture or in a feedlot, and in 2 different geographic regions for tropically adapted breeds. These data were used to estimate genetic parameters for the traits at each stage, and also to estimate the effect of market weight and finishing regimes on the phenotypic and genetic expression of each trait measured at the end of finishing stage. Results showed, for all traits, that the magnitude of the phenotypic expression increased across the stages and market-weight end-points for the end of finishing measures. Feedlot finishing decreased the age at slaughter, and increased fatness and muscling compared with pasture-finished animals. Heritabilities ranged from 0.13 to 0.58, with subjectively scored traits generally being lower than objectively measured traits. Additive genetic variances generally increased with stage of measurement, and with increasing market weight. Genetic correlations of the same measure across stages or market weights were all close to unity. Additive genetic variances of the various traits were similar for feedlot versus pasture finish groups, and the genetic correlation between each measure for feedlot and pasture finish was generally greater than 0.80. The effect of finishing geographic region (i.e. temperate versus subtropical environments) for the tropically adapted breeds had little effect on the size of the additive genetic variances or genetic correlations between traits across geographic regions.The results imply that changing the production system had a significant impact on the phenotypic expression of growth and body composition traits but little effect on the underlying genetic expression and subsequent ranking of sires (i.e. no evidence of genotype by production environment interactions). Therefore, these live animal measures could be used as selection criteria in genetic evaluation programs and may also be genetically correlated with abattoir carcass and meat quality traits.
Publisher: Elsevier BV
Date: 12-1998
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/AR02088
Abstract: Beef cattle data from temperate (TEMP, n = 3947) and tropically (TROP, n = 4137) adapted breeds were analysed to compute estimates of genetic and phenotypic correlations between animal, abattoir carcass, and meat quality measures. Live animal traits included: liveweight (S2LWT), scanned subcutaneous rump fat depth (S2P8), scanned eye muscle area (S2EMA), flight time (S1FT), and finishing average daily gain (FADG). Carcass traits included: hot carcass weight (CWT), retail beef yield percentage (RBY), intramuscular fat percentage (IMF), subcutaneous rump fat depth (P8), eye muscle length by width (ELW), and meat colour score (MEATC). Meat quality measures taken on 2 muscles [M. longissimus thoracis et lumborum (LTL) and M. semitendinosus (ST)] included: shear force of LTL (LTL_SF) and ST (ST_SF) compression of the ST (ST_C) cooking loss % of the LTL (LTL_CL%) and ST (ST_CL%) Minolta LTL L* (LTL_L*), a* (LTL_a*), ST a* (ST_a*) and consumer-assessed LTL tenderness score (LTL_TEND). Genetic and phenotypic correlations between animal measures and related carcass traits were moderate to very high for TEMP and TROP. Genetic correlations between S2LWT and CWT were 0.89 and 0.82, between S2P8 and P8 0.80 and 0.88, and between S2EMA and ELW 0.62 and 0.68, for TEMP and TROP, respectively. Genetic correlations between animal measures and other carcass traits varied moderate genetic correlations were estimated between S2P8 and RBY (–0.57, –0.19 for TEMP, TROP) and S2P8 and IMF (0.39, 0.23 for TEMP, TROP). Genetic correlations between animal and meat quality measures were moderate to low. For TEMP, moderate genetic correlations were estimated between S2P8 and LTL_TEND (0.38), FADG and ST_a* (–0.49), and FADG and LTL_TEND (0.45) and for TROP, S1FT and LTL_SF (–0.54), and S2EMA and LTL_L* (–0.46). Phenotypic correlations between animal and meat quality were generally low and close to zero. Several moderate to high genetic correlations existed between carcass and meat quality traits. In general, fatness measures were genetically correlated with tenderness (e.g. IMF and LTL_TEND 0.61, 0.31 for TEMP, TROP). CWT was genetically correlated with meat colour (CWT and LTL_L* 0.66, 0.60 for TEMP, TROP) and objective tenderness measures (CWT and ST_C –0.52, –0.22 for TEMP, TROP). Once again phenotypic correlations between carcass and meat quality were low, indicating that few phenotypic predictors of meat quality traits were identified. Several of the genetic correlations show that both animal and abattoir carcass traits may be of use as indirect measures for carcass and meat quality traits in multiple trait genetic evaluation systems.
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/AN14222
Abstract: For accurate calculation of reductions in greenhouse-gas (GHG) emissions, methodologies under the Australian Government’s Carbon Farming Initiative (CFI) depend on a valid assessment of the baseline and project emissions. Life-cycle assessments (LCAs) clearly show that enteric methane emitted from the rumen of cattle and sheep is the major source of GHG emissions from livestock enterprises. Where a historic baseline for a CFI methodology for livestock is required, the use of simulated data for cow–calf enterprises at six sites in southern Australia demonstrated that a 5-year rolling emission average will provide an acceptable trade off in terms of accuracy and stability, but this is a much shorter time period than typically used for LCA. For many CFI livestock methodologies, comparative or pair-wise baselines are potentially more appropriate than historic baselines. A case study of lipid supplementation of beef cows over winter is presented. The case study of a control herd of 250 cows used a comparative baseline derived from simple data on livestock numbers and class of livestock to quantify the emission abatement. Compared with the control herd, lipid supplementation to cows over winter increased livestock productivity, total livestock production and enterprise GHG emissions from 990 t CO2-e to 1022 t CO2-e. Energy embodied in the supplement and extra diesel used in transporting the supplement diminished the enteric-methane abatement benefit of lipid supplementation. Reducing the cow herd to 238 cows maintained the level of livestock production of the control herd and reduced enterprise emissions to 938 t CO2-e, but was not cost effective under the assumptions of this case study.
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/AN14319
Abstract: Sheep selected for high wool growth were previously shown to exhibit higher microbial protein outflow from the rumen and higher uptake of amino nitrogen in portal blood than those selected for low wool growth. This suggests that genetic selection for wool growth may induce changes in foregut physiology. This study was undertaken to determine whether differences in digesta kinetics, especially mean retention mime (MRT), are associated with differences in fleece production between sheep with low or high estimated breeding values (EBVs) for fleece weight. Twenty mature Merino wethers with uniform EBVs for liveweight were allocated to two groups of 10 animals on the basis of high or low EBVs for yearling fleece weight. Five sheep with low-EBVs and five sheep with high-EBVs for fleece weight groups were allocated in a crossover design to low and high feeding-level treatments, which comprised a blended hay diet fed at maintenance or 1.5 times maintenance. All sheep were given single doses of chromium-mordanted fibre and cobalt-EDTA as inert, non-digestible markers. Digesta kinetics was determined by analysis of the faecal marker excretion patterns using a compartmental model. Higher feed intakes from animals fed 1.5 times maintenance were associated with higher rates of wool growth and higher masses of indigestible fibre in the gut, but reduced MRT of digesta. Although sheep with higher EBVs for fleece weight had higher wool growth rates, there was no indication that these wool growth differences were associated with differences in digesta kinetics. The lack of interaction between feeding level and genotype suggests that MRT did not contribute to genotype differences in wool growth in sheep fed restricted intakes. The differences in wool growth among commercial Merino sheep with ergent fleece weight EBVs achieved by multi-trait selection are not attributable to differences in digesta kinetics, at least when feed is not available ad libitum.
Publisher: Cambridge University Press (CUP)
Date: 08-10-2014
DOI: 10.1017/S0007114513002936
Abstract: In the present study, following the measurement of methane emissions from 160 mature ewes three times, a subset of twenty ewes was selected for further emission and physiological studies. Ewes were selected on the basis of methane yield (MY g CH 4 /kg DM intake) being low (Low MY: sd below the mean n 10) or high (High MY: sd above the mean n 10) when fed a blended chaff ration at a fixed feeding level (1·2-fold maintenance energy requirements). The difference between the Low- and High-MY groups observed at the time of selection was maintained ( P = 0·001) when remeasured 1–7 months later during digesta kinetics studies. Low MY was associated with a shorter mean retention time of particulate ( P 0·01) and liquid ( P 0·001) digesta, less amounts of rumen particulate contents ( P 0·01) and a smaller rumen volume ( P 0·05), but not apparent DM digestibility ( P = 0·27) or urinary allantoin excretion ( P = 0·89). Computer tomography scanning of the sheep's rumens after an overnight fast revealed a trend towards the Low-MY sheep having more clearly demarcated rumen gas and liquid phases ( P = 0·10). These findings indicate that the selection of ruminants for low MY may have important consequences for an animal's nutritional physiology.
Publisher: Elsevier BV
Date: 03-2019
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-06-2014
Abstract: Sheep-specific genetic changes underlie differences in lipid metabolism between sheep and other mammals, and may have contributed to the production of wool. Jiang et al. sequenced the genome of two Texel sheep, a breed that produces high-value meat, milk, and wool. The genome information will provide an important resource for livestock production and aid in the understanding of mammalian evolution. Science , this issue p. 1168
Location: United Kingdom of Great Britain and Northern Ireland
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