Dorothy Robinson - Academia.edu (original) (raw)
Papers by Dorothy Robinson
Journal of Animal Science, 2015
Emissions of 710 ewes at pasture were measured for 1 h (between 09:00-16:30 h) in batches of 15 s... more 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.
Journal of Animal Science, 2013
Data from 2 previously published experiments, New South Wales (NSW; n = 161) and Western Australi... more Data from 2 previously published experiments, New South Wales (NSW; n = 161) and Western Australia (WA; n = 135), were used to test molecular value predictions (MVP), generated from commercially available gene markers, on economically important traits of Bos indicus (Brahman) cattle. Favorable tenderness MVP scores were associated with reduced shear force values of strip loin (LM) steaks aged 7 d from Achilles-hung carcasses (P ≤ 0.06), as well as steaks aged 1 (P ≤ 0.08) or 7 d (P ≤ 0.07) from carcasses hung from the pelvis (tenderstretch). Favorable tenderness MVP scores were also associated with improved consumer tenderness ratings for strip loin steaks aged 7 d and either Achilles hung (P ≤ 0.006) or tenderstretched (P ≤ 0.07). Similar results were observed in NSW for rump (top butt; gluteus medius) steaks, with favorable tenderness MVP scores associated with more tender (P = 0.006) and acceptable (P = 0.008) beef. Favorable marbling MVP scores were associated with improved (P ≤ 0.021) marbling scores and intramuscular fat (IMF) content in the NSW experiment, despite low variation in marbling in the Brahman cattle. For the WA experiment, however, there were no (P ≥ 0.71) relationships between marbling MVP and marbling scores or IMF content. Although residual (net) feed intake (RFI) was not associated (P = 0.63) with the RFI (feed efficiency) MVP, the RFI MVP was adversely associated with LM tenderness and acceptability of 7-d-aged Achilles-hung carcasses in NSW (P ≤ 0.031) and WA (P ≤ 0.037). Some other relationships and trends were noted between the MVP and the other traits, but few reached statistical significance, and none were evident in both experiments. Results from this study provide evidence to support the use of the tenderness MVP. The value of the marbling MVP, which was associated with marbling in only 1 herd, warrants further evaluation; however, there appears to be no evidence to support use of the RFI MVP in Brahman cattle.
Livestock Science, 2008
Investigations by Robinson [Robinson, D.L., 2007. Days to calving in artificially inseminated cat... more Investigations by Robinson [Robinson, D.L., 2007. Days to calving in artificially inseminated cattle: comparison of potential traits. Livestock Science 110, 174-180] concluded that the most useful trait for assessing fertility of artificially inseminated (AI) beef cows is AI days to calving (AIDC), a trait that mimics days to calving for naturally mated cows. Various fixed and random effects were fitted to AIDC to determine the best way of modelling lactation status of the cow, the effect of service sire, using smaller contemporary groups and lowering the penalty value for non-calvers. Fitting the time interval between calving and the start of mating either as a 10-level factor or a cubic spline function explained considerably more variation than fitting the standard 2level factor (wet or dry). Estimated permanent environmental effects of the cow were considerably reduced. This suggests that, if a cow calves late in the season (less than 60 days before she is inseminated), her fertility is reduced. Models should therefore account for this effect. If fitted, service sire explained 1.6% of phenotypic variation, compared to a much larger sire × contemporary group interaction (3% of phenotypic variation). It is therefore important to account for sire × contemporary group interactions. When the fertility of service sires is not being evaluated, service sires could be incorporated into the definition of contemporary groups. Ideally, breeders should be encouraged to formally record contemporary (or mating) groups. Reducing the size of contemporary groups (inferred from the data) by limiting the time interval between first and last inseminations from 120 to 60 days had only a marginal effect as did reducing the penalty for non-calvers from 21 to 10 days.
Australian Journal of Experimental Agriculture, 2001
Analyses were performed to test the relationship between retail beef yield percentage (RBY) and r... more Analyses were performed to test the relationship between retail beef yield percentage (RBY) and real time ultrasound measurements taken at weaning, entry to finishing and preslaughter for animals finished under pasture and feedlot conditions to meet domestic, Korean and Japanese market specifications. The first analysis tested the power of live animal measurements (scanned P8 fat depth, scanned eye muscle area and liveweight) to predict RBY and contrasted this with a model containing these live animal measurements plus a term (HERD × KILL ) which accounted for all known classification variables. This indicated that scanned P8 fat depth, measured at slaughter, was the most useful predictor of retail beef yield, accounting for 52% of the variation in RBY for the equation containing live animal measurements alone. The power of live animal measurements to predict RBY decreased as the time between scanning and slaughter increased. Models which included HERD × KILL predicted RBY accuratel...
Journal of Animal Science, 2016
Nitrate supplementation has been shown to be effective in reducing enteric methane emission from ... more Nitrate supplementation has been shown to be effective in reducing enteric methane emission from ruminants, but there have been few large-scale studies assessing the effects of level of nitrate supplementation on feed intake, animal growth, or carcass and meat quality attributes of beef cattle. A feedlot study was conducted to assess the effects of supplementing 0.25 or 0.45% NPN in dietary DM as either urea (Ur) or calcium nitrate (CaN) on DMI, ADG, G:F, and carcass attributes of feedlot steers ( = 383). The levels of NPN inclusion were selected as those at which nitrate has previously achieved measurable mitigation of enteric methane. The higher level of NPN inclusion reduced ADG as did replacement of Ur with CaN ( < 0.01). A combined analysis of DMI for 139 steers with individual animal intake data and pen-average intakes for 244 bunk-fed steers showed a significant interaction between NPN source and level ( = 0.02) with steers on the high-CaN diet eating less than those on the other 3 diets ( < 0.001). Neither level nor NPN source significantly affected cattle G:F. There was a tendency ( = 0.05) for nitrate-supplemented cattle to have a slower rate of eating (g DMI/min) than Ur-supplemented cattle. When adjusted for BW, neither NPN source nor inclusion level affected cross-sectional area of the LM or fatness measured on the live animal. Similarly, there were no significant main effects of treatments on dressing percentage or fat depth or muscling attributes of the carcass after adjustment for HCW ( > 0.05). Analysis of composited meat samples showed no detectable nitrates or nitrosamines in raw or cooked meat, and the level of nitrate detected in meat from nitrate-supplemented cattle was no higher than for Ur-fed cattle ( > 0.05). We conclude that increasing NPN inclusion from 0.25 to 0.45% NPN in dietary DM and replacing Ur with CaN decreased ADG in feedlot cattle without improving G:F.
Livestock Production Science, 1996
Simulated data were used to explore the consequences for genetic parameter estimates of effects s... more Simulated data were used to explore the consequences for genetic parameter estimates of effects such as negative dam-offspring covariances or additional sire or sire X year variation not accounted for in the estimation models. Extra variation between sires may result from the importation of superior genetic material, favouritism towards the offspring of certain sires or failure to randomise mating groups. The presence of additional sire or sire X year variation equivalent to 6% of the phenotypic variation resulted in negative estimates of approx.-0.5 for the correlation between direct and maternal genetic effects (ram). A similar value of ram was obtained from data generated as offspring = genetic + environmental terms-0.2 *(dam phenotype). This equation's final term has variance 0.04 * Var(dam phenotype), i.e., 4% of the phenotypic variation, but resulted in significant estimates of the permanent environmental effect of dam of the order of 8%. Fitting the dam's phenotypic value as a covariate reduced, but did not always eliminate, the negative estimates of ram, showing the extent to which an effect mediated by dam phenotype is necessarily confounded with genetic effects. If fitted, covariate coefficient estimates for dam phenotype were positive in datasets where no phenotypic dam-offspring relationship was simulated and otherwise negative, but biased.
Accident Analysis & Prevention, 2007
Animal Production Science, 2020
Context Knowledge of genetic and phenotypic variation and the accuracy of different measurement t... more 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 individual 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)....
Animal Production Science, 2019
Ruminant livestock contribute to atmospheric methane (CH4) from enteric microbial fermentation of... more 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 individual sheep. In total, 64 ewes were used in an incomplete block experiment with four experimental test periods (blocks). Ewes were chosen to represent the diversity 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) ...
Australian Journal of Agricultural Research, 2003
A total of 7622 cattle were measured for several weight and body composition traits in temperate ... more 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 fi...
Australian Journal of Agricultural Research, 2003
A total of 7622 cattle were measured for several weight and body composition traits in temperate ... more 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 fi...
Journal of animal science, 2016
Feed intake (FI), live weight (LW), and ADG were recorded over 31 d in ninety-six 12-month-old ew... more 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...
Journal of Animal Science, 2016
Medical Journal of Australia, Feb 6, 2006
A common-sense approach to reducing exposure to polluted air is required.
Road & Transport Research, 1998
Journal of Animal Science, 2015
Emissions of 710 ewes at pasture were measured for 1 h (between 09:00-16:30 h) in batches of 15 s... more 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.
Journal of Animal Science, 2013
Data from 2 previously published experiments, New South Wales (NSW; n = 161) and Western Australi... more Data from 2 previously published experiments, New South Wales (NSW; n = 161) and Western Australia (WA; n = 135), were used to test molecular value predictions (MVP), generated from commercially available gene markers, on economically important traits of Bos indicus (Brahman) cattle. Favorable tenderness MVP scores were associated with reduced shear force values of strip loin (LM) steaks aged 7 d from Achilles-hung carcasses (P ≤ 0.06), as well as steaks aged 1 (P ≤ 0.08) or 7 d (P ≤ 0.07) from carcasses hung from the pelvis (tenderstretch). Favorable tenderness MVP scores were also associated with improved consumer tenderness ratings for strip loin steaks aged 7 d and either Achilles hung (P ≤ 0.006) or tenderstretched (P ≤ 0.07). Similar results were observed in NSW for rump (top butt; gluteus medius) steaks, with favorable tenderness MVP scores associated with more tender (P = 0.006) and acceptable (P = 0.008) beef. Favorable marbling MVP scores were associated with improved (P ≤ 0.021) marbling scores and intramuscular fat (IMF) content in the NSW experiment, despite low variation in marbling in the Brahman cattle. For the WA experiment, however, there were no (P ≥ 0.71) relationships between marbling MVP and marbling scores or IMF content. Although residual (net) feed intake (RFI) was not associated (P = 0.63) with the RFI (feed efficiency) MVP, the RFI MVP was adversely associated with LM tenderness and acceptability of 7-d-aged Achilles-hung carcasses in NSW (P ≤ 0.031) and WA (P ≤ 0.037). Some other relationships and trends were noted between the MVP and the other traits, but few reached statistical significance, and none were evident in both experiments. Results from this study provide evidence to support the use of the tenderness MVP. The value of the marbling MVP, which was associated with marbling in only 1 herd, warrants further evaluation; however, there appears to be no evidence to support use of the RFI MVP in Brahman cattle.
Livestock Science, 2008
Investigations by Robinson [Robinson, D.L., 2007. Days to calving in artificially inseminated cat... more Investigations by Robinson [Robinson, D.L., 2007. Days to calving in artificially inseminated cattle: comparison of potential traits. Livestock Science 110, 174-180] concluded that the most useful trait for assessing fertility of artificially inseminated (AI) beef cows is AI days to calving (AIDC), a trait that mimics days to calving for naturally mated cows. Various fixed and random effects were fitted to AIDC to determine the best way of modelling lactation status of the cow, the effect of service sire, using smaller contemporary groups and lowering the penalty value for non-calvers. Fitting the time interval between calving and the start of mating either as a 10-level factor or a cubic spline function explained considerably more variation than fitting the standard 2level factor (wet or dry). Estimated permanent environmental effects of the cow were considerably reduced. This suggests that, if a cow calves late in the season (less than 60 days before she is inseminated), her fertility is reduced. Models should therefore account for this effect. If fitted, service sire explained 1.6% of phenotypic variation, compared to a much larger sire × contemporary group interaction (3% of phenotypic variation). It is therefore important to account for sire × contemporary group interactions. When the fertility of service sires is not being evaluated, service sires could be incorporated into the definition of contemporary groups. Ideally, breeders should be encouraged to formally record contemporary (or mating) groups. Reducing the size of contemporary groups (inferred from the data) by limiting the time interval between first and last inseminations from 120 to 60 days had only a marginal effect as did reducing the penalty for non-calvers from 21 to 10 days.
Australian Journal of Experimental Agriculture, 2001
Analyses were performed to test the relationship between retail beef yield percentage (RBY) and r... more Analyses were performed to test the relationship between retail beef yield percentage (RBY) and real time ultrasound measurements taken at weaning, entry to finishing and preslaughter for animals finished under pasture and feedlot conditions to meet domestic, Korean and Japanese market specifications. The first analysis tested the power of live animal measurements (scanned P8 fat depth, scanned eye muscle area and liveweight) to predict RBY and contrasted this with a model containing these live animal measurements plus a term (HERD × KILL ) which accounted for all known classification variables. This indicated that scanned P8 fat depth, measured at slaughter, was the most useful predictor of retail beef yield, accounting for 52% of the variation in RBY for the equation containing live animal measurements alone. The power of live animal measurements to predict RBY decreased as the time between scanning and slaughter increased. Models which included HERD × KILL predicted RBY accuratel...
Journal of Animal Science, 2016
Nitrate supplementation has been shown to be effective in reducing enteric methane emission from ... more Nitrate supplementation has been shown to be effective in reducing enteric methane emission from ruminants, but there have been few large-scale studies assessing the effects of level of nitrate supplementation on feed intake, animal growth, or carcass and meat quality attributes of beef cattle. A feedlot study was conducted to assess the effects of supplementing 0.25 or 0.45% NPN in dietary DM as either urea (Ur) or calcium nitrate (CaN) on DMI, ADG, G:F, and carcass attributes of feedlot steers ( = 383). The levels of NPN inclusion were selected as those at which nitrate has previously achieved measurable mitigation of enteric methane. The higher level of NPN inclusion reduced ADG as did replacement of Ur with CaN ( < 0.01). A combined analysis of DMI for 139 steers with individual animal intake data and pen-average intakes for 244 bunk-fed steers showed a significant interaction between NPN source and level ( = 0.02) with steers on the high-CaN diet eating less than those on the other 3 diets ( < 0.001). Neither level nor NPN source significantly affected cattle G:F. There was a tendency ( = 0.05) for nitrate-supplemented cattle to have a slower rate of eating (g DMI/min) than Ur-supplemented cattle. When adjusted for BW, neither NPN source nor inclusion level affected cross-sectional area of the LM or fatness measured on the live animal. Similarly, there were no significant main effects of treatments on dressing percentage or fat depth or muscling attributes of the carcass after adjustment for HCW ( > 0.05). Analysis of composited meat samples showed no detectable nitrates or nitrosamines in raw or cooked meat, and the level of nitrate detected in meat from nitrate-supplemented cattle was no higher than for Ur-fed cattle ( > 0.05). We conclude that increasing NPN inclusion from 0.25 to 0.45% NPN in dietary DM and replacing Ur with CaN decreased ADG in feedlot cattle without improving G:F.
Livestock Production Science, 1996
Simulated data were used to explore the consequences for genetic parameter estimates of effects s... more Simulated data were used to explore the consequences for genetic parameter estimates of effects such as negative dam-offspring covariances or additional sire or sire X year variation not accounted for in the estimation models. Extra variation between sires may result from the importation of superior genetic material, favouritism towards the offspring of certain sires or failure to randomise mating groups. The presence of additional sire or sire X year variation equivalent to 6% of the phenotypic variation resulted in negative estimates of approx.-0.5 for the correlation between direct and maternal genetic effects (ram). A similar value of ram was obtained from data generated as offspring = genetic + environmental terms-0.2 *(dam phenotype). This equation's final term has variance 0.04 * Var(dam phenotype), i.e., 4% of the phenotypic variation, but resulted in significant estimates of the permanent environmental effect of dam of the order of 8%. Fitting the dam's phenotypic value as a covariate reduced, but did not always eliminate, the negative estimates of ram, showing the extent to which an effect mediated by dam phenotype is necessarily confounded with genetic effects. If fitted, covariate coefficient estimates for dam phenotype were positive in datasets where no phenotypic dam-offspring relationship was simulated and otherwise negative, but biased.
Accident Analysis & Prevention, 2007
Animal Production Science, 2020
Context Knowledge of genetic and phenotypic variation and the accuracy of different measurement t... more 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 individual 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)....
Animal Production Science, 2019
Ruminant livestock contribute to atmospheric methane (CH4) from enteric microbial fermentation of... more 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 individual sheep. In total, 64 ewes were used in an incomplete block experiment with four experimental test periods (blocks). Ewes were chosen to represent the diversity 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) ...
Australian Journal of Agricultural Research, 2003
A total of 7622 cattle were measured for several weight and body composition traits in temperate ... more 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 fi...
Australian Journal of Agricultural Research, 2003
A total of 7622 cattle were measured for several weight and body composition traits in temperate ... more 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 fi...
Journal of animal science, 2016
Feed intake (FI), live weight (LW), and ADG were recorded over 31 d in ninety-six 12-month-old ew... more 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...
Journal of Animal Science, 2016
Medical Journal of Australia, Feb 6, 2006
A common-sense approach to reducing exposure to polluted air is required.
Road & Transport Research, 1998