Within-breed selection is sufficient to improve terminal crossbred beef marbling: a review of reciprocal recurrent genomic selection

Reciprocal recurrent selection is the selection of purebreds for crossbred performance and takes advantage of additive and non-additive variance by using pedigreed progeny performance records. Developed in maize, the adoption of this approach in livestock breeding has been limited to the pork and poultry industries; genomic selection may facilitate its extension into the beef industry by replacing pedigree. The literature regarding the relative importance of additive versus non-additive variance and reciprocal recurrent genomic selection models was reviewed. The potential for using reciprocal recurrent genomic selection in a terminal Wagyu × Angus cross scenario was examined. Non-additive variance is more important for fitness traits and accounts for a small proportion of variance related to production traits such as marbling. In general, reciprocal recurrent selection was not significantly better at improving performance of crossbreds than was traditional selection within parental breeds using only additive variance in the studies examined. Simulation studies showed benefits of including dominance or breed-specific allele effects in prediction models but advantages were small as more realistic simulations were examined. On the basis of the evidence, it is likely that in a terminal two-way cross-beef scenario utilising Wagyu sires and Angus dams, where selection emphasis is on marbling, selection of purebreds on the basis of additive variance will allow substantial progress to be realised.

Genomic analysis of purebred and crossbred Angus cattle demonstrates opportunity for multi-breed evaluation

Context Overseas studies have quantified production differences of Hereford Angus crossbreds compared with purebred Angus for a range of traits including growth, carcass and reproductive traits. Aim This study aimed to quantify breed and heterosis effects using genomics. Methods Thirty Hereford and 30 Angus sires were mated to 1100 Angus cows and heifers in a large commercial herd run on pasture at Musselroe Bay, Tasmania. Approximately 1650 calves were born. Steers (743) were grown for an average of 23 months and then slaughtered. Results Heterozygosity effects were significant for birth, weaning and carcass weight and also loin eye-muscle area. On average, higher-quality (percentile) Hereford than Angus bulls were used. Breeding values were calculated for sires and could be compared with a common base given they also had BREEDPLAN breeding values published. Conclusions When heterozygosity was accounted for and when compared on a common base, progeny of average Angus sires were superior to progeny of Hereford sires for birthweight, carcass weight, eye-muscle area and intramuscular fat. Implications The method of benchmarking breeds using crossbred cattle and genomics provides a model for rapid adoption of multi-breed estimated breeding values, which is desirable for commercial beef producers.