Genetic trends of resilience indicators related to recovery capacity and environmental responsiveness in Nelore cattle from different selection lines

Abstract

This study aimed to estimate genetic trends of resilience indicators derived from individual growth curves of Nellore cattle, from birth to yearling weight. Two resilience indicators were calculated from the residuals of the growth curves: first-order autocorrelation (R_auto) and skewness. Data comprised 5,294 animals from three selection lines at the Institute of Animal Science (Sertãozinho, SP, Brazil): NeS (selected for post-weaning weight), NeT (selected for post-weaning weight and feed efficiency), and NeC (under stabilizing selection). It included 38,961 body weight records (1980–2023), pedigree information for 13,351 animals, and genotypes for 3,860 animals with 383,856 SNPs after quality control. Genomic estimated breeding values (GEBVs) were obtained using the single-step genomic best linear unbiased prediction (ssGBLUP) method under a Bayesian framework. Genetic trends were assessed by regressing GEBVs on birth year within each line. Annual means of GEBVs and phenotypic averages were also calculated for two periods (1981–1985 and 2019–2023). Regression models revealed significant differences among herds (P < 0.001). Genetic trends for R_auto were 0.0000184 ± 0.0000164 (NeC), –0.000224 ± 0.0000108 (NeS), and –0.000175 ± 0.00000943 (NeT), suggesting slight improvement in recovery capacity in selected lines. Skewness showed similar trends, with coefficients of 0.000893 ± 0.0000712 (NeC), –0.00126 ± 0.000067 (NeS), and –0.00159 ± 0.0000659 (NeT). Phenotypic differences varied by indicator and line. For R_auto, only NeS showed no significant differences between periods, with values –0.19 ± 0.04 (NeC), –0.04 ± 0.02 (NeS), and –0.12 ± 0.02 (NeT). For skewness, significant differences were observed only in NeC (0.19 ± 0.08), compared to 0.02 ± 0.06 (NeS) and 0.01 ± 0.06 (NeT). These findings indicate that resilience indicators vary genetically and phenotypically among Nellore lines, highlighting that such differences are likely driven by distinct selection criteria, which may influence the genetic potential for resilience through correlated responses.