The value of recording live animal and carcase scan traits for the genetic selection of lean meat yield in lamb

Abstract

The value of a carcase is highly influenced by its saleable meat yield. Direct measures of lean meat yield (LMY) are currently not commercially available due to the high cost of measurement through the 'gold standard' of computed tomography (CT). Therefore, the objective of this study was to assess the use of post-weaning scan traits, carcase traits, and a dual-energy x-ray absorptiometry (DEXA)-derived lean, as indicator traits for selection to improve LMY in lamb. DEXA-derived lean was strongly genetically correlated to CT lean (r_g = 0.75). This suggests that DEXA (which can be recorded under commercial processing conditions) has value as an indicator trait for CT lean. However, there are different implications for predicted genetic gains for ram breeding and progeny testing situations due to availability of records from different classes on animals. Since a ram breeder sells most animals as breeding stock and there is limited access to slaughter records, only 50% of potential genetic gains (compared to selection for CT lean) could be achieved through DEXA alone. The addition of post-weaning traits increased potential genetic gains to 67%. Therefore, the ram breeding industry will still need to rely on the correlated trait measured on the live animals and the rate of genetic gain will be slower. As seedstock producers will struggle to record DEXA and CT traits in sufficient numbers, resource populations such as the Information Nucleus Flock will continue to be required to validate the parameters presented in this study and improve the ability for ram breeders to make effective selection decisions for LMY improvement. Furthermore, since there are unfavourable associations between LMY and eating quality, genetic improvement of LMY will need to be managed, and eating quality included in the breeding objective for Australian lamb breeders.