Live animal measurements, carcass composition and plasma hormone and metabolite concentrations in male progeny of sires differing in genetic merit for beef production

Abstract

In genetic improvement programmes for beef cattle, the effect of selecting for a given trait or index on other economically important traits, or their predictors, must be quantified to ensure no deleterious consequential effects go unnoticed. The objective was to compare live animal measurements, carcass composition and plasma hormone and metabolite concentrations of male progeny of sires selected on an economic index in Ireland. This beef carcass index (BCI) is expressed in euros and based on weaning weight, feed intake, carcass weight and carcass conformation and fat scores. The index is used to aid in the genetic comparison of animals for the expected profitability of their progeny at slaughter. A total of 107 progeny from beef sires of high (n 5 11) or low (n 5 11) genetic merit for the BCI were compared in either a bull (slaughtered at 16 months of age) or steer (slaughtered at 24 months of age) production system, following purchase after weaning (8 months of age) from commercial beef herds. Data were analysed as a 2 3 2 factorial design (two levels of genetic merit by two production systems). Progeny of high BCI sires had heavier carcasses, greater ( P , 0.01) muscularity scores after weaning, greater ( P , 0.05) skeletal scores and scanned muscle depth pre-slaughter, higher ( P , 0.05) plasma insulin concentrations and greater ( P , 0.01) animal value (obtained by multiplying carcass weight by carcass value, which was based on the weight of meat in each cut by its commercial value) than progeny of low BCI sires. Regression of progeny performance on sire genetic merit was also undertaken across the entire data set. In steers, the effect of BCI on carcass meat proportion, calculated carcass value (c/kg) and animal value was positive ( P , 0.01), while a negative association was observed for scanned fat depth pre-slaughter and carcass fat proportion ( P , 0.01), but there was no effect in bulls. The effect of sire expected progeny difference (EPD) for carcass weight followed the same trends as BCI. Muscularity scores, carcass meat proportion and calculated carcass value increased, whereas scanned fat depth, carcass fat and bone proportions decreased with increasing sire EPD for conformation score. The opposite association was observed for sire EPD for fat score. Results from this study show that selection using the BCI had positive effects on live animal muscularity, carcass meat proportion, proportions of high-value cuts and carcass value in steer progeny, which are desirable traits in beef production.

Genetic differences based on a beef terminal index are reflected in future phenotypic performance differences in commercial beef cattle

“…Therefore, the close to unity regression coefficient of phenotypic performance for a trait on its respective EBV across all data (Table 2) was expected. Such conclusions are corroborated by previously documented regression coefficients that related genetic merit to phenotypic performance using both national (McHugh et al, 2014) and experimental data (Clarke et al, 2009a). The genetic standard deviation of carcass weight in the national genetic evaluation is 25 kg.…”

“…The impact of animal genetic differences for performance traits on subsequent phenotypic performance has been documented in controlled experiments that compared animals divergent in genetic merit for an individual trait (Crews et al, 2006;Keane and Diskin, 2007;Campion et al, 2009) or a combination (i.e. index) of traits (Clarke et al, 2009a). Such controlled experiments (Crews et al, 2006;Campion et al, 2009;Clarke et al, 2009a), however have been limited in population size and diversity in production systems represented.…”

“…index) of traits (Clarke et al, 2009a). Such controlled experiments (Crews et al, 2006;Campion et al, 2009;Clarke et al, 2009a), however have been limited in population size and diversity in production systems represented. Genotype-by-environment (G × E) interactions have been documented in some controlled studies (Campion et al, 2009) but not others (Clarke et al, 2009a).…”

“…Such controlled experiments (Crews et al, 2006;Campion et al, 2009;Clarke et al, 2009a), however have been limited in population size and diversity in production systems represented. Genotype-by-environment (G × E) interactions have been documented in some controlled studies (Campion et al, 2009) but not others (Clarke et al, 2009a). The robustness of genetic evaluations for terminal traits across contrasting production systems, representative of what exist in commercial herds, has therefore not been thoroughly elucidated.…”

Intake, growth and carcass traits in male progeny of sires differing in genetic merit for beef production

“…The phenotypic traits investigated in the present study include all of those actually included in the BCI. Analysis on the effect of BCI on live animal muscular and skeletal scores, scanned muscle and fat depth, carcass composition and carcass value (based on commercial value of meat cuts obtained in carcass dissection work) is discussed elsewhere (Clarke et al, 2009). …”