W Pitchford1, M Hebart1, S Lee1
1University Of Adelaide
Data from 12 different data sets totalling 6997 animals from 433 sires across four breeds (Angus, Charolais, Hereford, and Limousin), and 3 finishing regimes (Pasture, Short Fed and Long Fed) were analysed. Carcass traits were regressed on BREEDPLAN sire estimated breeding values (EBVs) to examine the extent to which the Meat Standards Australian (MSA) index of commercial animals is related to BREEDPLAN EBVs. Sire variance components were estimated for each dataset to determine whether the genetic variance in MSA index and its indicator traits changed with carcass weight.
The sire variation in carcass traits differed between feeding regimes for all carcass traits except ossification. The largest difference between finishing systems was for intramuscular fat (IMF) where there was a 5.5-fold increase in the sire standard deviation for the Long fed versus Pasture finishing systems. Furthermore, in the 4 Regional Combination datasets the genetic (sire) correlation between Pasture and Short Fed steers for IMF was only 0.58, indicating there was a significant genotype by environment interaction.
Michelle has a PhD in quantitative genetics from the University of Adelaide. She has over 20 years experience working in animal science on various projects ranging from the genetics of lamb survival and sustainable grazing of saline land, to maternal productivity in cattle. She is currently a lecturer in research methodology at the University of Adelaide.