Stayability and consecutive rebreeding ability associated to carcass and growth traits in Brazilian Nellore cattle: A Bayesian framework

Abstract

Stayability(STAY) plays a substantial role in Nellore breeding programs in Brazil, but it does not differentiate cows with different rebreeding successes. Thus, we propose consecutive rebreeding ability (CRA) as a new multi-categorical trait related to the capacity of consecutive parturitions at calving intervals of less than 14 months. The heritability for CRA and its genetic correlations with stayability at 52 (STAY52) and 76 (STAY76) months, rib eye area (REA), subcutaneous backfat thickness (BF), age at first calving (AFC), post-yearling scrotal circumference (PSC), and post-yearling weight (PW) were estimated. The pedigree information provided a genealogical relationship matrix that contained 2,042,151 animals. The genetic parameters were estimated by multiple-trait Bayesian inference using the THRGIBBS1F90 software. The heritability estimates (posterior means and posterior standard deviations) for CRA, STAY52, STAY76, REA, BF, PW, AFC and PSC were, respectively, 0.11 (0.036), 0.092 (0.009), 0.15 (0.013), 0.35 (0.015), 0.13 (0.013), 0.34 (0.012), 0.17 (0.005) and 0.41 (0.021). In general, for a proposed trait (such as CRA) be considered as a replacement for existing ones, then it must be able to significantly increase the rate of genetic progress, that is a function of genetic variation, selection intensity and generation interval. Thus, the current STAY76 remains the most appropriate criterion for Nellore breeding programs. In this context, STAY76 still being recommended as a simple and practical trait for long-term Nellore cow selection. Additionally, the genetic association for CRA would not have a negative genetic impact on subcutaneous backfat thickness (BF), age at first calving (AFC) and post-yearling scrotal circumference (PSC).