Genetic control of uniformity of yearling weight in Nellore cattle

In livestock breeding, genetic canalization is studied because of the interest to improve uniformity of production and to increase resilience. Several studies have confirmed the existence of genetic canalization characterized by genetic variation in the size of the environmental variance. In beef cattle, we have found evidence for genetic variation in environmental variance of body weight at 550 days of age, i.e. yearling weight (YW). However, a limited number of investigations have been done to elucidate genes controlling environmental variance. The aim of our study was identify genomic regions controlling environmental variance of YW through a genome-wide association study (GWAS). As response variable, we used the log-transformed variance of estimated residuals for each paternal half-sib family (n=423) from the mean model of YW of a double hierarchical generalized linear model (DHGLM). The GWAS was performed using a Bayesian variable selection method (BayesC) and 333,877 single nucleotide polymorphisms (SNP). In total, four SNPs on chromosomes 2, 5, 8 and 10 were strongly associated with environmental variance of YW (Bayes Factor > 20). Together, they explained less than 5% of the genetic variance, indicating that the environmental variance is a complex trait determined by several genes with small effects, like body weight itself. Within these regions, promising genes involved in metabolism (LPL, ATP6V1B2, OSBPL8, GLI2) and response to stress (SLC18A1, HIF1A, BBS10) were found. Our findings show that studying the genetics of environmental variance of body weight reveals not only metabolic genes, but also genes related to response to stress and adaptation.