A large proportion of genetic variation in cow and ewe body composition is independent of yearling composition

Abstract

Commercial beef and sheep producers have adopted using condition score for management of cows and ewes to maximise productivity. Significant premiums are being paid for bulls and rams with higher-fat breeding values based on young animal measurements, with the aim of increased resilience in adult female progeny. Aims. The aim of this study was to quantify the relationship between adult body condition score and young muscle and fat and also the genetic variation in condition that is independent of yearling traits. Methods. Published genetic parameters for four large data sets from Angus and tropically adapted cattle, and composite and Merino sheep were used to partition genetic variation in adult condition that is associated with, or independent of, young composition measures. Key results. One genetic standard deviation in young muscle or fat was associated with approximately just 0.1 adult body condition scores. Approximately ¾ of the genetic variation in adult body condition score (BCS) is independent of genetic variation in young weight and composition traits. Conclusions and implications. Producers need to be careful with premiums paid for bulls and rams with superior yearling composition traits with the aim of changing adult BCS. The best way to achieve this is for seedstock breeders to record and report breeding values for cow and ewe BCS.