Estudo genético quantitativo de características morfológicas, produtivas, reprodutivas e de carcaça em bovinos nelore

• Autor(a) principal: Soares, Byanka Bueno
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/11218
• topic: Amostragem de Gibbs; Associação genética; Características morfológicas; Zebuínos; Genetic association; Gibbs sampling; Morphological traits; Zebu; CIENCIAS AGRARIAS::ZOOTECNIA::GENETICA E MELHORAMENTO DOS ANIMAIS DOMESTICOS

The aim of this study was to estimate the genetic parameters of functional biotype indicator traits through the MERCOS methodology as well as the relationship between these and performance, carcass, and reproductive traits, in Nellore cattle using Bayesian Inference. The data set used contained information on 12,060 Nellore cattle born between 2001 and 2020, provided by HoRa Hofig Ramos. Visual scores data set from 4,175 Nellore cattle were used, such as muscling (M), physical structure (PS), racial (R), conformation (C), navel (N), and sacrum bone (SAC). Besides, body weights at 120 (W120), 210 (W210), 365 (W365), and 450 (W450) days of age, rib eye area (REA), backfat thickness (BF), rump fat thickness (RF), scrotal circumference at 365 (SC365) and 450 (SC450) days of age, stayability (STAY), probability of precocious calving (PPC) and age at first calving (AFC). The genealogy information used to compose the kinship matrix was provided by the National Association of Breeders and Researchers. Bi-trait Bayesian analyzes were performed using a linear-threshold model to combine linear and categorical traits, or threshold-threshold, when both traits analyzed, were categorical. The heritability estimates obtained are very wide, varying from low to high magnitude: 0.21; 0.28; 0.25; 0.25; 0.15; 0.18; 0.27; 0.28; 0.34; 0.44; 0.42; 0.46; 0.46; 0.50; 0.53; 0.38; 0.54 and 0.10 for M, BS, R, C, N, SAC, W120, W210, W365, W450, REA, BF, RF, SC365, SC450, STAY, PPC and AFC, respectively. These results indicate genetic selection feasibility and obtaining genetic gains, mainly for growth, carcass, scrotal circumference, STAY, PPC and visual scores as muscling, physical structure, racial and conformation. Still, genetic selection for visual scores is feasible. The maternal heritability estimates for W120 and W210 were: 0.16 and 0.13, respectively, indicating dam genetic effects on the progenies' performance until the weaning, for growth traits. The genetic correlations between visual scores were positive and from moderate to high, ranging from 0.25 to 0.89, except for the estimates obtained between visual scores N and SAC. The genetic correlations between visual scores and growth traits were, in general, moderate to high, except for R with W365 and W450, C with W210 and W450, O with W120, W210, and W450, and SAC with W210, W365, and W450 that were low. The genetic correlations between visual scores and carcass traits were, in general, low, except for REA with PS and SAC, which were moderate. The genetic correlations between visual scores and reproduction traits were generally low, except for M with PPC, PS with STAY, R with SC450, C with SC365, SC450, STAY and AFC, N with STAY and AFC, and SAC with SC365, STAY, and AFC, which were moderate. Estimates of genetic correlation indicate that direct selection for visual score traits may influence body weight and vice versa, and these responses are favorable. Even so, higher genetic gain for visual scores is expected if the selection is carried out directly for them, than selection for growth, reproduction, or carcass traits. However, selection for W365 and W450 may result in higher genetic gains in M and selection for REA in SAC, than direct selection for these traits. The selection of animals with higher scores, mainly for M, PS, and C scores can be used as selection criteria to get genetic gain for growth, sexual precocity, and fertility in Nellore cattle.