Effects of inbreeding on production traits and genetic evaluations in Guzerá beef cattle raised under tropical conditions.

The objectives of this study were to evaluate the influence of inbreeding on growth traits and body measurements, as well as on the estimation of genetic parameters and genetic trends in Guzerá cattle. Phenotypic records of 4,212 animals selected for postweaning weight from Guzerá Breeding Program of Advanced Beef Cattle Research Center were utilized. The pedigree file contained records from 7,213 animals born from 1928 to 2019. The traits analyzed were: birth weight (BW), weights adjusted to 210, 378 and 550 days of age (W210, W378 and W550, respectively), chest girth at 378 and 550 days of age (CG378 and CG550), scrotal circumference (SC), and hip height at 378 and 550 days of age (HH378 and H550). Linear regression was used to evaluate the effects of inbreeding on traits. Genetic parameters were obtained using models including or not the effect of inbreeding as a covariate. Inbreeding had negative effects (P ≤ 0.01) on BW (-0.09 kg), W378 (-2.86 kg), W550 (-2.95 kg), HH378 (-0.10 cm), and H550 (-0.29 cm). The lowest and highest heritability estimates were obtained for W210 (0.21 ± 0.07) and HH550 (0.57 ± 0.06), respectively. The genetic correlations were strong and positive between all traits, ranging from 0.44 ± 0.08 (SC x HH) to 0.99 ± 0.01 (W378 x W550). Spearman correlations between EBVs obtained with or without inbreeding effect ranged from 0.968 to 0.995 (P < 0.01). The results indicate loss of productive performance in inbred animals. However, the inclusion of inbreeding coefficient in genetic evaluation models did not alter the magnitude of genetic parameters or genetic trends for the traits studied.

Spatialization of breeding values of Brangus animals associated with climatic, physical, and socio-economic factors.

This study was realized to analyze the combinations of climatic, physical, and socio-economic variables on distribution of breeding values for performance characteristics and scrotal circumference of Brangus cattle. Records of 84,703 Brangus animals, born from 2000 to 2010 distributed in 65 farms in Brazil were used. The characteristics analyzed were average daily gain from birth to weaning and from weaning to yearling (WW and YW), visual scores of conformations (WC and YC), muscle score (WM and YM), precocity score (WP and YS), and size score (WS and YS) at weaning and yearling and scrotal circumference (SC) at yearling. Components of (co)variance estimated through the animal model employing methodology to AIREML. Mean estimates of direct heritability obtained for visual scores at weaning (WC 0.16, WM 0.16, WP 0.19, and WS 0.22) were lower than those obtained at yearling (YC 0.28, YM 0.26, YP 0.24, and YS 0.40). WW had heritability greater than YW (0.27 and 0.12) and a heritability of 0.36 obtained for SC. Canonical, discriminant, and cluster analyses were performed in the SAS® 9.4 program. Three clusters of genetic values averages per farm were formed according to climatic, physical, and socio-economic variables. Brangus animals are from states of RS, PR, SP, MG, GO, MG, and MS. The highest breeding values were strongly related to thermal amplitude and municipality area. Spatial distribution of the breeding value of Brangus animals can help in the development of environmental indices, genetic evaluations, and the choice of animals for certain environments.

Reatividade e desempenho em cordeiros cruzados Suffolk x Île-de-France / Reactivity and performance in Suffolk x Île-de-France crossbred lambs

Objetivou-se estimar as correlações fenotípicas (r) entre os escores comportamentais de reatividade aplicados durante e após a pesagem e os ganhos médios diários de peso (GMD) de cordeiros cruzados Suffolk x Île-de-France, aos 30, 60 e 90 dias de idade, bem como estudar o efeito da habituação dos animais ao manejo. As variáveis avaliadas por meio de escores foram: interferência do avaliador para o animal entrar na balança (INT), vocalização (VOC), movimentação (MOV), tensão (TEN), movimentos exploratórios (ME), postura de orelhas (ORE) e o teste de tipos de marcha (TM). Os resultados das correlações de Spearman obtidos entre os escores indicam que VOC, MOV e TEN podem ser consideradas como características importantes na expressão da reatividade de ovinos em ambiente de restrição. Já o GMD parece não estar associado com a reatividade dos cordeiros avaliados. Por fim, aos 90 dias de idade, os cordeiros apresentaram-se menos reativos, em função do aprendizado por habituação.

The aim of this study was to estimate the phenotypic correlations (r) between behavioral reactivity scores obtained during and after weighing, and the average daily weight gains (ADG) of Suffolk x Île-de-France cross lambs, at 30, 60 and 90 days of age, as well as to study the effect of habituation towards handling. The variables assessed through scores were: interference of the observer for the animal to enter the weighing crate (INT), vocalization (VOC), movement (MOV), tension (TEN), exploratory movements (EM), ears posture (EP) and the gait speed test (qualitative flight time test) (GS). The results of the Spearman correlations indicate that VOC, MOV and TEN may be considered important traits in the expression of reactivity in sheep assessed while restrained. On the contrary, ADG does not seem to be correlated with reactivity. Finally, at 90 days of age, the lambs were less reactive, due to learning by habituation.