90. Genetic Evaluation of Feed Efficiency Traits in Brazilian Angus Cattle.

Abstract

Feed efficiency is a critical component of sustainable animal production, influencing economic viability, environmental impact, and biological performance. As feed constitutes the largest expense in beef production, even minor improvements in feed efficiency can yield substantial economic benefits. The goal of this study was to estimate the genetic parameters for key feed efficiency traits in Brazilian Angus cattle, to assess their potential for genetic improvement and to understand the genetic relationship among the different traits. The statistical model used in this study was similar to the model currently used by the Brazilian Angus Association in their official genetic evaluation, which includes dry matter intake (DMI), residual feed intake (RFI), and residual average daily gain (RADG) in a three-trait animal model based on the pedigree relationship matrix. Phenotypic records from 641 purebred Brazilian Angus beef cattle were used in this study. The number of observations after quality control were 600 for RFI, 553 for RADG, and 573 for DMI. The tested group had an average age of 474 (±131) days. Fixed effects included in the statistical model were test age and contemporary group (defined as the concatenation of feed efficiency test group and feed efficiency test ID). Genetic parameters were estimated using the mentioned three-traits model under Bayesian framework, using the GIBBSF90+ software. Moderate heritabilities were estimated for RFI (h² = 0.29, 95% HPD 0.09 to 0.49), DMI (h² = 0.41, 95% HPD 0.17 to 0.63), and RADG (h² = 0.23, 95% HPD 0.043 to 0.41), suggesting that genetic selection could lead to meaningful improvement in these traits. In addition, genetic correlations were estimated among the traits. For instance, RADG had a moderate negative correlation with RFI (rg= -0.68, 95% HPD -0.99 to -0.27), indicating that animals with higher growth efficiency for a given intake tend to have lower feed consumption and better digestive efficiency. The DMI and RFI traits had a strong positive genetic correlation (rg = 0.92, 95% HPD 0.7 to 1) meaning that animals consuming more feed tend to have larger residual feed intake. The genetic correlation estimated between RADG and DMI (rg= -0.47, 95% HPD -0.96 to 0.052) was not statistically different from zero, suggesting that selection for RADG may not result in a consistent correlated response in DMI. In conclusion, to our knowledge, this study provides the first estimates of genetic parameters for feed efficiency traits in this Brazilian Angus population, demonstrating the feasibility of genetic selection for improving feed efficiency in this population. Future work will include GWAS for these three traits to identify the associated genomic regions, as well as estimate the genetic correlation of these feed efficiency traits with other economically important traits.