Sire Type Research Articles

Carcase weight and dressing percentage are increased using Australian Sheep Breeding Values for increased weight and muscling and reduced fat depth

Pre-slaughter live weight, dressing percentage, and hot standard carcase weight (HCWT) from the 2007, 2008, 2009 and 2010 birth-years of the Information Nucleus Flock Lambs (n=7325) were analysed using linear mixed effects models. Increasing the sire breeding value for post-weaning weight (PWWT), and c-site eye muscle depth (PEMD), and reducing the sire breeding value for fat depth (PFAT) all had positive impacts on HCWT. The magnitude of the PWWT effect was greater in pure bred Merinos compared to Maternal and Terminal sired progeny. The improved HCWT resulting from increased PEMD was entirely due to its impact on improving dressing percentage, given that it had no impact on pre-slaughter live weight. There were marked differences between sire types and dam breeds, with pure-bred Merinos having lower pre-slaughter weight, reduced dressing percentage, and lower HCWT than progeny from Terminal and Maternal sired lambs or progeny from Maternal (1st cross) dams.

Effects of service sire on prenatal mortality and prolificacy in ewes.

Ability to select service sires that minimize partial or complete losses of pregnancy could have major economic impacts in sheep production systems. This study tested the null hypothesis that survival of potential progeny did not vary with breed type of service sire or among individual rams. Data included 980 ewes on 10 farms; each ewe was pregnant to 1 of 67 rams of 12 breeds. Number of conceptuses was estimated once during pregnancy by ultrasonography, either transrectal (embryos) or transabdominal (fetuses), and was compared with number of lambs born to estimate losses. Data were examined first for number of lambs born and second for documented losses. Individual service sires affected number born (P < 0.001), which varied from 0.70 to 2.45 lambs per pregnant ewe. The main effects of breed type on lambs born were not significant, but breed types of both service sires (P < 0.0002) and ewes (P < 0.001) interacted with diagnosed number of conceptuses. Lambs born varied with ewe age (P < 0.0001) and among farms (P < 0.0001), and statistically, farms interacted with number of diagnosed conceptuses (P < 0.0001); season had no effect. In documented losses, there were both main effects of individual service sire and a service sire × number of diagnosed embryos interaction (P < 0.005). Thus, ewes bred to some rams were more apt to lose single pregnancies, whereas ewes bred to other rams were more apt to lose 1 or more embryos or fetuses from multiple pregnancies. Breed type of service sire affected (P < 0.05) prenatal death. Complete losses of single conceptuses tended to be greater in ewes bred to black-faced or hair-type rams (service sire breed type × number of diagnosed conceptuses; P < 0.09). Breed type of ewes also varied in incidence of complete losses (P < 0.05); hair-type ewes (46%) lost more (P < 0.02) documented conceptuses from examination to birth than black-faced (27%), white-faced (20%), or dairy-type (25%) ewes. Greater losses of singles than of multiples occurred in black-faced (37% vs. 18%) and hair-type (64% vs. 27%) ewes than in other breeds (ewe breed type × number of conceptuses; P < 0.03) per ewe. Surprisingly, purebred conceptuses were lost less often (24%) than crossbreds (36.4%; P < 0.002). Selection of rams based on records of prenatal losses in ewes they serviced may be a method to decrease embryonic and fetal wastage. However, further study to determine repeatability of differences among service sires from year to year will be required.

Nutritional background, sire type and dam type affect saturated and monounsaturated (oleic) fatty acid concentration of lambs reared for meat production in Australia

This study investigated the effect of finishing diet, sire type and dam type on major saturated (C12:0, 14:0, 16 : 0 and 18:0) and monounsaturated (oleic; C18:1cis) fatty acid concentrations in meat from lambs grown at eight production locations across Australia. Sires were selected from Merino, maternal and terminal meat breeds; while the dams consisted of ~80% pure Merino and 20% crossbred (Border Leicester × Merino) types. Lambs were generally maintained under extensive pasture conditions, but were fed grain, hay or feedlot pellets when the pasture supply was limited. Lambs were slaughtered over 3 consecutive years (2008–10), with 28–30 slaughter days per year. At 24 h post-mortem, 20-g muscle samples (longissimus lumborum: LL) were taken for fatty acid determination. Lambs from Hamilton, Katanning and Kirby had a higher (P &lt; 0.001) concentration of major saturated (palmitic and stearic) and oleic acids in meat that is proposed to be associated with those lambs being fed diets higher in cereal grain content. Saturated fatty acids, except lauric acid, were lower (P &lt; 0.02) in lambs sired by Merino or terminal type than lambs sired by maternal type. The use of Merino as the sire or dam reduced (P &lt; 0.001) the major saturated fatty acids in LL. Crossbred dam type increased (P &lt; 0.01) the oleic acid concentration in the LL, but sire type had no effect. The results demonstrate that the finishing diet type or sire type or dam type can significantly influence the concentration of major saturated (palmitic, stearic) and/or oleic acids in meat from lambs produced under different production systems in Australia.

Sire and liveweight affect feed intake and methane emissions of sheep confined in respiration chambers

Daily methane production and feed intake were measured on 160 adult ewes, which were the progeny of 20 sires and 3 sire types (Merino, dual-purpose and terminal) from a genetically diverse flock. All animals were housed in individual pens and fed a 50/50 mix of chaffed lucerne and oaten hays at 20 g/kg liveweight (LW), with feed refusals measured for at least 10 days before the first of three 22-h measurements in respiration chambers (RC). Feed was withdrawn at 1600 h on the day before each RC test to encourage the ewes to eat the entire ration provided for them in the RC. After the first 1-day RC test, the sheep were returned to their pens for a day, then given a second 1-day RC test, followed by another day in their pens, then a third RC test. After all animals had been tested, they were ranked according to methane emissions adjusted for feed intake in the RC and on the previous day, enabling 10 low and 10 high methane animals to be chosen for repeat measurement. No variation between sires nor consistent effects of LW on feed eaten (%FE, expressed as per cent of feed offered) was evident in the 10 days before the first RC measurement. However, significant differences between sires (equivalent to an estimated heritability of 41%) were identified for %FE during the 2nd and 3rd days of RC testing (2 and 4 days after the initial RC test). The analysis of all data showed that methane emissions in the RC were related to feed intake on the day of testing and the two previous days (all P<0.0005). Before correcting for feed intake on previous days, there was some variation between sires in methane yield, equivalent to an estimated heritability of 9%. Correction for feed intake on the 2 previous days halved the residual variation, allowing other effects to be detected, including effects of LW, twins reared as singles, test batch, RC and test-day effects, but estimated sire variation fell to zero. In order to avoid potential biases, statistical models of methane emissions in the RC need to consider potential confounding factors, such as those identified as significant in this study.

Increasing weight gain during pregnancy results in similar increases in lamb birthweights and weaning weights in Merino and non-Merino ewes regardless of sire type

Birthweight is the single largest determinant of survival in lambs and can be predicted from ewe liveweight at conception and liveweight changes during pregnancy. These prediction equations are known for Merino ewes, but it is unknown if they are applicable to non-Merino breeds. We tested the hypothesis that increasing conception weights of ewes will increase the birthweights, survival to weaning and weaning weights of their lambs, irrespective of ewe or sire breed, but that non-Merino lamb birthweights would be less responsive than Merino lamb birthweights, to changes in ewe liveweights during pregnancy. Ewe liveweight, lamb birth and weaning weight records from Merino sires mated to Merino ewes (MM), Border Leicester Merino (Maternal) sires mated to Merino ewes, Poll Dorset or Suffolk (Terminal) sires mated to Merino ewes (TM), and Terminal sires mated to Border Leicester Merino ewes (TMAT) were analysed from the 2007 to 2011 lambings of eight information nucleus flocks. Lamb birthweights increased by 0.032 ± 0.0012 kg from MM ewes and 0.024 ± 0.0026 kg from TMAT ewes with every 1-kg increase in conception weight (P &lt; 0.001). Irrespective of breed, for every 1-kg increase in liveweight change during early and late pregnancy, lamb birthweights increased by 0.021 ± 0.0019 kg and 0.034 ± 0.0019 kg and weaning weights by 0.26 ± 0.013 kg and 0.09 ± 0.011 kg, respectively (P &lt; 0.001). Survival to weaning of single, twin and triplet lambs was highest for lambs from TMAT ewes (89.3% ± 1.25, 84.6% ± 1.49 and 73.4% ± 2.35) and lowest for TM ewes (80.2% ± 1.89, 72.8% ± 2.09 and 57.4% ± 2.98; P &lt; 0.001). Coefficients relating ewe liveweight change during pregnancy to lamb birthweights are similar for Merino and Maternal ewes, however conception weights of Maternal ewes are significantly heavier than Merino ewes when run together, and lamb birthweights from Maternal ewes are less responsive to ewe conception weights. The coefficients reported in this paper will enable development of optimum management guidelines for single-, twin- and triple-bearing Maternal ewes.

Factors affecting the colour of lamb meat from the longissimus muscle during display: The influence of muscle weight and muscle oxidative capacity

Spectrophotometric measures were used to determine the redness:browness (R630/R580) of 4238 lamb longissimus muscle after 3days under simulated display. The results were analysed using linear mixed effects models. Environmental factors represented by effects such as kill group and site of production produced the greatest variation of up to 2.76 units in R630/R580. Isocitrate dehydrogenase activity, reflecting muscle oxidative capacity, reduced R630/R580 by 0.5 units. Selection for high muscling sires increased R630/R580 by 0.27 units, likely due to changes in muscle oxidative capacity. Lamb carcass weight also increased R630/R580 by 0.5 units. Analysis of genotypic factors influencing lamb size and growth rate such as sire type and dam breed further supported that increased growth rate improves meat R630/R580. Our findings suggest that breeding for increased growth rate and increased muscle weight could result in Australian lamb meat retaining its red colour for extended periods whilst on display.

Reproductive performance in the Sheep CRC Information Nucleus using artificial insemination across different sheep-production environments in southern Australia

The present paper covers reproductive performance in an artificial-insemination (AI) program of the Sheep CRC Information Nucleus with 24 699 lambs born at eight locations in southern Australia across five lambings between 2007 and 2011. Results from AI with frozen semen compared well with industry standards for natural mating. Conception rates averaged 72%, and 1.45 lambs were born per ewe pregnant for Merino ewes and 1.67 for crossbreds. Lamb deaths averaged 21% for Merino ewes and 15% for crossbreds and 19%, 22% and 20% for lambs from ewes that were mated to terminal, Merino and maternal sire types, respectively. Net reproductive rates were 82% for Merino ewes and 102% for crossbreds. From 3198 necropsies across 4 years, dystocia and starvation-mismothering accounted for 72% of lamb deaths within 5 days of lambing. Major risk factors for lamb mortality were birth type (single, twin or higher order), birthweight and dam breed. Losses were higher for twin and triplet lambs than for singles and there was greater mortality at relatively lighter and heavier birthweights. We conclude that reproductive rate in this AI program compared favourably with natural mating. Lamb birthweight for optimum survival was in the 4–8-kg range. Crossbred ewes had greater reproductive efficiency than did Merinos.

Intramuscular fat in the longissimus muscle is reduced in lambs from sires selected for leanness

Selection for lean growth through Australian Sheep Breeding Values (ASBVs) for post weaning weight (PWWT), eye muscle depth (PEMD) and c-site fat depth (PFAT) raises concerns regarding declining intramuscular fat (IMF) levels. Reducing PFAT decreased IMF by 0.84% for Terminal sired lambs. PEMD decreased IMF by 0.18% across all sire types. Female lambs had higher IMF levels and this was unexplained by total carcass fatness. The negative phenotypic association between measures of muscling (shortloin muscle weight, eye muscle area) and IMF, and positive association between fatness and IMF, was consistent with other literature. Hot carcass weight increased IMF by 2.08% between 12 and 40kg, reflective of development of IMF as lambs approach maturity. Selection objectives with low PFAT sires will reduce IMF, however the lower impact of PEMD and absence of a PWWT effect, will enable continued selection for lean growth without influencing IMF. Alternatively, the negative impact of PFAT could be off-set by inclusion of an IMF ASBV.

Discovery and trait association of single nucleotide polymorphisms from gene regions of influence on meat tenderness and long-chain omega-3 fatty acid content in Australian lamb

Whole genome association studies in humans have shown a strong relationship between omega-3 levels in plasma and single nucleotide polymorphisms (SNP) located close to genes whose protein products are involved in the biosynthesis of long-chain omega-3 fatty acids. In sheep and other livestock species, the calpain/calpastatin system is the principal influence on natural variation in meat tenderness between animals. Using targeted next generation sequencing, we sequenced the fatty acid desaturase locus (FADS1/2/3), ELOVL2 and SLC26A10 and the calpain/calpastatin (CAPN1/2/3 and CAST) gene loci of 35 industry sires from the Australian flock. A total of 753 SNP were identified and 182 of these SNP were selected for incorporation onto a research SNP panel that represented the genetic variation across the nine genes. A total of 1252 animals were genotyped from the Australian Sheep CRC Information Nucleus Flock for these SNP and the genomic association was calculated for omega-3 fatty acid content and objective meat tenderness in lamb. Six SNP within CAST and CAPN2 showed association with shear force at Day 5 post-mortem at a significance level of P ≤ 0.01. When these were fitted simultaneously in a mixed-model analysis with fixed effects and covariates, three SNP remained significant. These SNP each had an unfavourable effect on shear force of between 1.1 and 1.8 N, with a combined effect of 4.1 N. The frequency of the favourable alleles in the progeny measured indicates that these SNP hold good potential for improving the management of meat tenderness across Merino, Border Leicester and Terminal sire types. No SNP within the FADS1/2/3, ELOVL2 and SLC26A10 gene regions were associated with lamb muscle omega-3 levels. This indicates that genetic variation in the long-chain omega-3 biosynthesis pathway genes analysed here may not be important for omega-3 content in lamb within the Information Nucleus Flock population.

Evaluation of whole body and subregional DXA precision

Selection for lean growth through Australian Sheep Breeding Values (ASBVs) for post weaning weight (PWWT), eye muscle depth (PEMD) and c-site fat depth (PFAT) raises concerns regarding declining intramuscular fat (IMF) levels. Reducing PFAT decreased IMF by 0.84% for Terminal sired lambs. PEMD decreased IMF by 0.18% across all sire types. Female lambs had higher IMF levels and this was unexplained by total carcass fatness. The negative phenotypic association between measures of muscling (shortloin muscle weight, eye muscle area) and IMF, and positive association between fatness and IMF, was consistent with other literature. Hot carcass weight increased IMF by 2.08% between 12 and 40 kg, reflective of development of IMF as lambs approach maturity. Selection objectives with low PFAT sires will reduce IMF, however the lower impact of PEMD and absence of a PWWT effect, will enable continued selection for lean growth without influencing IMF. Alternatively, the negative impact of PFAT could be off-set by inclusion of an IMF ASBV.

Can a herb and white clover mix improve the performance of multiple-bearing ewes and their lambs to weaning?

The productive performance of highly fecund ewes and their progeny on ryegrass-based swards is limited in late pregnancy and lactation. Alternative herbages, such as chicory, plantain and red and white clover, have the potential to improve performance levels. In the present study, 49 twin- and 42 triplet-bearing Romney composite ewes bred to either Suffolk or Romney rams were allocated to one of three nutritional treatments from Day 131 of pregnancy [19 twin ewes on a ryegrass–white clover sward mix (Rye/WC); 16 twin ewes on a plantain–ryegrass sward mix (Plant/Rye); 14 twin ewes on a chicory–plantain–red and white clover sward mix (Herb); 13 triplet ewes on Rye/WC; 16 triplet ewes on Plant/Rye; and 13 triplet ewes on Herb] and remained on these sward treatments with their lambs until 75 days after the midpoint of the lambing period (L75). Nutritional treatment had no effect (P &gt; 0.05) on ewe liveweight, body condition score (BCS) or non-esterified fatty acid and β-hydroxybutyrate concentrations on Day 145 of pregnancy. At L75, ewes on the Herb treatment sward were heavier than ewes on Plant/Rye (70.75 ± 1.31 v. 61.43 ± 1.28 kg, respectively) and had a higher BCS than ewes on either Plant/Rye or Rye/WC (2.7 ± 0.1, 2.2 ± 0.1 and 2.3 ± 0.1, respectively). Sire type and nutritional treatment had no affect (P &gt; 0.05) on lamb birthweight or weight at L75. At L20, lambs born to ewes on the Herb sward treatment were heavier than those on the Rye/WC and Plant/Rye treatments (8.74 ± 0.23 v. 7.98 ± 0.23 and 7.79 ± 0.22 kg, respectively; P &lt; 0.05). Neither birth rank, sire type nor ewe treatment had any effect (P &gt; 0.05) on maximum heat production on a per kg liveweight basis or total heat production. Romney-sired lambs on the Herb sward treatment had higher (P &lt; 0.05) survival rates than those on the Rye/WC sward treatment (97.8% v. 61.7%, respectively). However, no such relationship was observed in lambs born to Suffolk sires (79.8% v. 84.8%, respectively). The survival response resulted in greater (P &lt; 0.05) total liveweight of Romney-sired lambs at L75 per ewe on the Herb nutritional treatment than on the Rye/WC treatment (61.6 ± 5.0 v. 36.7 ± 4.6 kg, respectively) a relationship not observed (P &gt; 0.05) in Suffolk-sired lambs. In conclusion, the present study indicates that there is the potential to improve the productive performance of multiple-bearing ewes and their lambs by grazing on a Herb sward mix.

Effects of growth path, sire type, calving time and sex on growth and carcass characteristics of beef cattle in the agricultural area of Western Australia

Growth, carcass characteristics and meat quality of the steer and heifer progeny of autumn (AC: March–April) and winter (WC: June–July) calving cows following weaning in January in each of 3 years (2003–05) were measured. The cows were mated to sires with a high estimated breeding value for either retail beef yield (RBY), intramuscular fat (IMF) or both RBY and IMF. After weaning, the progeny entered one of three growth paths until slaughter at an average steer liveweight of 500 kg: (i) fast – fast growth from weaning on a high concentrate feedlot diet; (ii) slow – slow growth from weaning (~0.6 kg/day) to 400 kg liveweight followed by growth at over 1 kg/day on high quality pasture; or (iii) comp. – 10% weaning weight loss, immediately after weaning followed by compensatory or rapid growth of over 1 kg/day on high quality pasture. Steers on the fast growth path had higher (P &lt; 0.001) P8 fat thickness than those on the slow or comp. growth paths whereas heifers on the fast growth path only had higher (P &lt; 0.001) P8 fat thickness than those on the slow growth path. Animals on the fast growth treatment had higher (P &lt; 0.001) levels of IMF% than the slow animals which were higher (P &lt; 0.001) than the comp. growth treatment. AUS-MEAT and US marbling scores were not different among growth paths. Animals finished on the fast growth path had a lower (P &lt; 0.001) RBY% than those on either the slow or comp. growth paths. The RBY-sired progeny had higher (P &lt; 0.001) finishing liveweight and hot standard carcass weight than either RBY and IMF or IMF-sired animals. IMF-sired progeny had higher (P &lt; 0.01) rib fat thickness than either RBY or RBY- and IMF-sired animals. There was also a similar trend for P8 fat thickness but the effects were not significant. The RBY-sired animals had lower AUS-MEAT marbling scores (P &lt; 0.01), US marbling scores (P &lt; 0.001) and levels of IMF% (P &lt; 0.01) than either of the other two sire treatments. RBY-sired animals also had higher (P &lt; 0.001) estimated RBY% than those from the IMF sires while those by RBY and IMF sires were intermediate and not significantly different from either. Calving time had little influence on most carcass characteristics. However, WC animals tended to be fatter and have higher marbling scores than AC animals. The IMF% was higher (P &lt; 0.01) in WC animals from RBY and IMF sires than in the corresponding AC animals. Heifers had lighter slaughter liveweight, carcass weight, were fatter and had higher marbling scores than steers. Heifers also had lower (P &lt; 0.001) RBY% than the steers. Ossification scores for heifers were higher (P &lt; 0.001) than for steers by ~30 units in AC calves and by 20 units in WC calves. The results of this experiment confirm the effectiveness of using sires with high estimated breeding value for the required characteristics in producing the desired improvements in the progeny. The absence of any interactions of sire type with growth path indicates that differences between sire types will be similar regardless of environmental conditions. Animals raised on a faster growth path after weaning produce carcasses with more fat and more IMF% than those grown on slower growth paths.

Performance of steer progeny of sires differing in genetic potential for fatness and meat yield following postweaning growth at different rates. 2. Carcass traits

The steer progeny of sires genetically diverse for fatness and meat yield were grown at different rates from weaning to feedlot entry and effects on growth, carcass and meat-quality traits were examined. The present paper, the second of a series, reports the effects of genetic and growth treatments on carcass traits. A total of 43 sires, within three ‘carcass class’ categories, defined as high potential for meat yield, marbling or both traits, was used. Where available, estimated breeding values for the carcass traits of retail beef yield (RBY%) and intramuscular fat (IMF%) were used in selection of the sires, which were drawn from Angus, Charolais, Limousin, Black Wagyu and Red Wagyu breeds, to provide a range of carcass sire types across the three carcass classes. Steer progeny of Hereford dams were grown at either conventional (slow: ~0.5 kg/day) or accelerated (fast: ~0.7 kg/day) rates from weaning to feedlot entry weight, with group means of ~400 kg. Accelerated and conventionally grown groups from successive calvings were managed to enter the feedlot at similar mean feedlot entry weights at the same time for the 100-day finish under identical conditions. Faster-backgrounded groups had greater fat levels in the carcass than did slower-backgrounded groups. Dressing percentages and fat colour were unaffected by growth treatment, whereas differences in ossification score and meat colour were explained by age at slaughter. There were significant effects of sire type for virtually all carcass traits measured in the progeny. Differences in hot standard carcass weight showed a clear advantage to European types, with variable outcomes for the Angus and Wagyu progeny. Sire selection by estimated breeding values (within the Angus breed) for yield and/or fat traits resulted in expected differences in the progeny for those traits. There were large differences in both meat yield and fatness among the types of greatest divergence in genetic potential for those traits, with the Black Wagyu and the Angus IMF clearly superior for IMF%, and the European types for RBY%. The Angus IMF progeny performed as well as that of the Black Wagyu for all fatness traits. Differences in RBY% among types were generally reflected by similar differences in eye muscle area. Results here provide guidelines for selecting sire types to target carcass traits for specific markets. The absence of interactions between growth and genetic treatments ensures that consistent responses can be expected across varying management and production systems.

Performance of steer progeny of sires differing in genetic potential for fatness and meat yield following post-weaning growth at different rates. 1. Growth and live-animal composition

The present experiment, ‘Regional Combinations’, examined growth, and carcass- and meat-quality traits in the progeny of sires genetically diverse for fatness and meat yield when grown at different rates from weaning to feedlot entry. The present paper is the first of several papers describing results from the New South Wales site, one of four in the project. It reports the effects on growth and body composition of steers during backgrounding and feedlot finishing phases. A total of 43 sires within three carcass-class categories, defined as high potential for meat yield, for marbling or for both traits, was used, based on estimated breeding values for retail beef yield and intramuscular fat. Sires were drawn from Angus, Charolais, Limousin, Black Wagyu and Red Wagyu breeds, providing a range of carcass sire types across the three carcass classes. Matings were by artificial insemination to Hereford dams from a single herd. Steer progeny were grown at conventional (slow: ~0.5 kg/day) or accelerated (fast: ~0.7 kg/day) rates from weaning to feedlot entry weight, targeting group means of 400 kg. Accelerated and conventionally grown groups from successive calvings entered the feedlot at similar entry liveweights at the same time, then having identical management during the 100-day finishing phase before slaughter. Within finishing cohorts, fast backgrounding growth resulted in increased subcutaneous fatness at feedlot entry in steers of all carcass types. Slow growth during backgrounding resulted in faster (compensatory) growth in the feedlot in all classes and sire types. This increased the deposition of fat in slow-backgrounded steers compared with that in fast-backgrounded steers during feedlotting, and thus reduced the difference between the groups in P8 and rib fat at feedlot exit. However, there did appear to be an advantage in the level of compensation in the feedlot in favour of those sire types with a genetic propensity for faster growth. Backgrounding growth rate affected body composition and the rate of weight gain during finishing. Faster growth produced more subcutaneous fat during both backgrounding and finishing. Steer progeny groups clearly showed the expected responses in growth and body composition, on the basis of the genetic potential of their sires.

Erratum to: Performance of steer progeny of sires differing in genetic potential for fatness and meat yield following postweaning growth at different rates. 2. Carcass traits

The steer progeny of sires genetically diverse for fatness and meat yield were grown at different rates from weaning to feedlot entry and effects on growth, carcass and meat-quality traits were examined. The present paper, the second of a series, reports the effects of genetic and growth treatments on carcass traits. A total of 43 sires, within three 'carcass class' categories, defined as high potential for meat yield, marbling or both traits, was used. Where available, estimated breeding values for the carcass traits of retail beef yield (RBY%) and intramuscular fat (IMF%) were used in selection of the sires, which were drawn from Angus, Charolais, Limousin, Black Wagyu and Red Wagyu breeds, to provide a range of carcass sire types across the three carcass classes. Steer progeny of Hereford dams were grown at either conventional (slow: ~0.5 kg/day) or accelerated (fast: ~0.7 kg/day) rates from weaning to feedlot entry weight, with group means of ~400 kg. Accelerated and conventionally grown groups from successive calvings were managed to enter the feedlot at similar mean feedlot entry weights at the same time for the 100-day finish under identical conditions. Faster-backgrounded groups had greater fat levels in the carcass than did slower-backgrounded groups. Dressing percentages and fat colour were unaffected by growth treatment, whereas differences in ossification score and meat colour were explained by age at slaughter. There were significant effects of sire type for virtually all carcass traits measured in the progeny. Differences in hot standard carcass weight showed a clear advantage to European types, with variable outcomes for the Angus and Wagyu progeny. Sire selection by estimated breeding values (within the Angus breed) for yield and/or fat traits resulted in expected differences in the progeny for those traits. There were large differences in both meat yield and fatness among the types of greatest divergence in genetic potential for those traits, with the Black Wagyu and the Angus IMF clearly superior for IMF%, and the European types for RBY%. The Angus IMF progeny performed as well as that of the Black Wagyu for all fatness traits. Differences in RBY% among types were generally reflected by similar differences in eye muscle area. Results here provide guidelines for selecting sire types to target carcass traits for specific markets. The absence of interactions between growth and genetic treatments ensures that consistent responses can be expected across varying management and production systems.

Growth implants reduced tenderness of steaks from steers and heifers with different genetic potentials for growth and marbling1

The objective of this study was to evaluate the effect of growth implants on the carcass characteristics and tenderness of steers and heifers with different genetic potentials for growth, lean meat yield production, and marbling. Two experiments were conducted. Experiment 1 evaluated Angus steers sired by bulls with high EPD for retail product yield or marbling. Implant treatment was imposed randomly within sire groups. Loins (Institutional Meat Purchasing Specifications 180) were collected from each carcass and cut into three 2.54-cm steaks aged for 7, 14 and 21 d to evaluate tenderness. The second experiment evaluated steers and heifers of British and Continental breed descent. Steers and heifers were slaughtered after 120 d on feed. Loin sections were collected, and one 2.54-cm steak aged 7 d was used for tenderness analysis. When implants were used in Angus steers, HCW and LM area increased, whereas internal fat and marbling decreased (P < 0.01). In Angus steers, sire type did not affect shear force values of steaks; however, implant use significantly increased shear force values (P < 0.01). Carcasses from cattle of Continental breed descent were significantly heavier than carcasses of British breed descent with larger LM area, slightly less fat, and a reduced yield grade (P < 0.01). Also, steer carcasses were heavier than heifer carcasses with larger LM (P < 0.05), but no effect of sex on fat depth, internal fat, yield grade or marbling was observed. No significant interactions were seen between growth implant and breed or between growth implant and sex for shear force values. Shear force values were significantly less for steaks from steers and heifers of British decent compared with steers and heifers of Continental descent (P < 0.01). Steaks from implanted steers and heifers had significantly (P < 0.01) greater shear force values than steaks from steers and heifers not implanted. Use of growth implants in growing cattle resulted in significantly heavier carcass weights, larger LM area, and reduced internal fat. However, implant use also reduced the amount of marbling along with contributing to reduced tenderness. Complicating the tenderness issue is the increased shear force values reported for heifers as well as steers of Continental breed descent. Use of implants may contribute to tenderness variability because of different animal responses to implants.

Predicting tissue distribution and partitioning in terminal sire sheep using x-ray computed tomography1

The utility of x-ray computed tomography (CT) scanning in predicting carcass tissue distribution and fat partitioning in vivo in terminal sire sheep was examined using data from 160 lambs representing combinations of 3 breeds (Charollais, Suffolk, and Texel), 3 genetic lines, and both sexes. One-fifth of the lambs were slaughtered at each of 14, 18, and 22 wk of age, and the remaining two-fifths at 26 wk of age. The left side of each carcass was dissected into 8 joints with each joint dissected into fat (intermuscular and subcutaneous), lean, and bone. Chemical fat content of the LM was measured. Tissue distribution was described by proportions of total carcass tissue and lean weight contained within the leg, loin, and shoulder regions of the carcass and within the higher-priced joints. Fat partitioning variables included proportion of total carcass fat contained in the subcutaneous depot and intramuscular fat content of the LM. Before slaughter, all lambs were CT scanned at 7 anatomical positions (ischium, midshaft of femur, hip, second and fifth lumbar vertebrae, sixth and eighth thoracic vertebrae). Areas of fat, lean, and bone (mm(2)) and average fat and lean density (Hounsfield units) were measured from each cross-sectional scan. Areas of intermuscular and subcutaneous fat were measured on 2 scans (ischium and eighth thoracic vertebra). Intramuscular fat content was predicted with moderate accuracy (R(2) = 56.6) using information from only 2 CT scans. Four measures of carcass tissue distribution were predicted with moderate to high accuracy: the proportion of total carcass (R(2) = 54.7) and lean (R(2) = 46.2) weight contained in the higher-priced joints and the proportion of total carcass (R(2) = 77.7) and lean (R(2) = 55.0) weight in the leg region. Including BW in the predictions did not improve their accuracy (P > 0.05). Although breed-line-sex combination significantly affected fit of the regression for some tissue distribution variables, the values predicted were changed only trivially. Within terminal sire type animals, using a common set of prediction equations is justified. Tissue distribution and fat partitioning affect eating satisfaction and efficiency of production and processing; therefore, including such carcass quality measures in selection programs is increasingly important, and CT scanning appears to provide opportunities to do so.

Evaluation of reciprocal differences in Bos indicus × Bos taurus backcross calves produced through embryo transfer: II. Postweaning, carcass, and meat traits1

Angus (A) x Bos indicus (B; Brahman or Nellore) reciprocal backcross, embryo transfer calves belonging to 28 full-sib families were evaluated for differences in feedyard initial BW, feedyard final BW, carcass weight, LM area, adjusted fat thickness, intramuscular fat, and Warner-Bratzler shear force. Two methods of analysis were investigated; method I made no distinction between how the F(1) parents were produced, whereas method II distinguished the 2 types of F(1) parents (AB vs. BA, corresponding to A x B vs. B x A, respectively). No significant reciprocal differences for these weight and carcass traits were detected under method I analyses, although the same trend existed for subsequent BW rankings as for birth weight and weaning weight. For each weight phase, the cross that involved a larger proportion of B in the sire in relation to the amount in the dam (F(1) x A and B x F(1)) ranked heavier than the respective reciprocal cross (A x F(1) and F(1) x B). As a whole, A backcross calves had larger (P < 0.001) LM area, more (P < 0.001) marbling, and lower (P < 0.001) Warner-Bratzler shear force than B back-cross calves, but no consistent trends were detected between reciprocal crosses for any of these traits, in contrast with the trends observed for the weight traits. Furthermore, males were heavier than females entering (P < 0.001) and leaving (P < 0.001) the feedyard, produced a heavier carcass (P < 0.001), and had larger LM area (P < 0.05) with less adjusted fat (P < 0.001). No difference existed between the sexes for Warner-Bratzler shear force or marbling. No interactions involving sex, sire type, and dam type were observed for any of these traits. The results were similar under methods I and II analyses, with the exception that a significant sire type x dam type interaction was observed for initial feedyard BW. Results from this study suggest that for weight-related traits, both the breed constitution of the embryo transfer calf and the cross that produces the calf play an important role in its ultimate performance for B crossbred calves. For body composition and meat-related traits, it appears that the breed makeup of the embryo transfer calf itself is more important to animal performance than the specific cross used to produce the calf.

Voluntary food intake, live-weight gain, carcass quality and food conversion in contrasting genotypes of weaned suckler-bred bulls finished intensively on a cereal-based diet

AbstractA bull beef finishing experiment was conducted with the objective of comparing physical performance of constrasting genotypes of suckler-bred bull beef animals finished intensively on a cereal-based diet at approximately 12 to 13 months of age. Nine bulls per genotype were drawn from weaned, bull calves born to one of two dam types (Belgian Blue×Holstein/Friesian (BB) or Simmental×Holstein/Friesian (SIM)) and which had been sired by one of two contrasting sire types (Aberdeen Angus (AA) or Charolais (CH)). Bull calves were weaned at approximately 8 months of age and the finishing experiment ran from approximately 9 months of age until slaughter at 12 to 13 months of age. Cereal-based concentrate diets were offered to all bulls on an ad libitum basis throughout the experimental finishing period. Dry matter intake (DMI), live-weight gain (LWG), food conversion ratio (FCR), and carcass slaughter characteristics were quantified.Average daily LWG was 2·07, 2·11, 2·34 and 2·65 kg/day, average FCR was 5·14, 5·06, 4·70 and 4·12 kg DMI per kg LWG and average age at slaughter was 387, 381, 374 and 366 days for the AA/BB, AA/SIM, CH/BB and CH/SIM bulls respectively. These figures showed that CH sired bulls grew faster ( P&lt;0·001), finished at an earlier age ( P&lt;0·01) and had better food conversion ratios ( P&lt;0·01) than AA sired bulls. CH sired bulls also produced heavier carcasses (P&lt;0·001) with better conformation ( P&lt;0·001) than AA sired bulls. Average cold carcass weights (CCW) at slaughter were 309, 318, 348 and 365 kg and average conformation scores (15-point scale) at slaughter were 9·28, 10·28, 12·39 and 12·75 for the AA/BB, AA/SIM, CH/BB and CH/SIM bulls respectively. Finished bulls from SIM dams had higher LWGs (P&lt;0·01) and produced heavier carcasses (P&lt;0·05) than bulls from BB dams. No statistically significant differences in fat score (15-point scale) were seen between any of the breed combinations with fat scores of 7·50, 7·25, 6·75 and 6·75 for the AA/BB, AA/SIM, CH/BB and CH/SIM bulls respectively. No significant differences in average daily food intake were observed between breed combinations in the experiment with average daily DMI being 10·6, 10·6, 11·0 and 10·9 kg/day for AA/BB, AA/SIM, CH/BB and CH/SIM bulls respectively.Overall, there was little evidence to suggest that the rate of bull LWG declined to bring about any meaningful reduction in productivity as average bull live weight increased from approximately 9 months of age until slaughter at 12 to 13 months of age. When finished on a nutrient-rich, cereal-based concentrate diet, excellent animal performance and commercially acceptable carcasses can be produced from the UK suckler herd using genetically superior sires of either traditional UK or continental beef cattle breeds. Results from this study indicate that CH sired bulls out-performed AA sired bulls, especially when produced from SIM cows.

Variation in protein abundance profiles in the M. semitendinosus of lambs bred from sires selected on the basis of growth and muscling potential

Relative abundance of proteins localised in the nuclear-enriched, total cell membrane and cytosolic fractions of the semitendinosus muscle was compared between lambs bred from control (C), high muscling (M), and high growth rate (G) sires. In total, 31 proteins were identified whose abundance was differentially regulated between sire type. Differences in hind-limb muscle development between M lambs and C and G lambs were reflected in levels of proteins that regulate or function in cellular mechanisms of protein and energy metabolism. Despite no apparent difference in hind-limb muscle growth in G lambs compared to C, G lambs exhibited marked differences in proteins involved in regulation and function of energy metabolism. These results detail pathways that can be specifically targeted to enhance muscle accretion and growth in lambs. The development of means to manipulate these cellular mechanisms may yield greater gains in muscle accretion and growth rate than breeding on the basis for genetic capacity alone.