Efeitos ambientais e genéticos sobre escores visuais e ganho de peso à desmama de animais formadores da raça Brangus

Abstract

RESUMO -Estudaram-se os efeitos da idade da vaca ao parto e da idade do animal à desmama, bem como os efeitos genéticos aditivo direto e materno e da heterozigose individual, sobre os escores visuais de conformação, precocidade e musculatura e ganho de peso do nascimento à desmama, de animais formadores da raça Brangus. Foram analisados 53.683, 45.136, 52.937 e 56.471 dados de conformação, precocidade e musculatura à desmama e ganho de peso do nascimento à desmama, respectivamente, de animais nascidos entre 1986 e 2002, provenientes do arquivo zootécnico da empresa Gensys Consultores Associados S/C Ltda. Os efeitos de ambiente e genéticos sobre as características em estudo foram analisados pelo método de quadrados mínimos usando modelos matemáticos que incluíram grupo de contemporâneos como variável classificatória e a idade da vaca ao parto, a idade do animal à desmama e os efeitos aditivo direto e materno e da heterozigose individual como co-variáveis. Todos os efeitos incluídos nos modelos afetaram significativamente as características avaliadas, com exceção do efeito da idade da vaca ao parto sobre o ganho de peso do nascimento à desmama e do efeito aditivo materno sobre todas as características estudadas. Os efeitos ambientais e genéticos revelaram-se importantes fontes de variação para as características estudadas e devem, pois, ser considerados na distinção e comparação dos animais para seleção.Palavras-chave: características de crescimento, conformação, efeitos de ambiente, heterozigose individual, musculatura, precocidadeEnvironmental and genetic effects on visual scores and average daily weight gain at the weaning of animals used to form the Brangus breed ABSTRACT -The objective of this work was to study the effects of age of cow at calving (IPV) and age of calf at weaning (IDD) as well as the direct additive genetic effects (AD) and maternal (AM), and the individual heterozygosity (HI) on visual scores of conformation (CD), precocity (PD) and musculature (MD) and average daily weight gain from birth to weaning (GND), for animals used to form the Brangus breed. The study analyzed 53,683, 45,136, 52,937 and 56,471 records on CD, PD, MD and GND, respectively for animals born from 1986 to 2002. The data were provided by "Gensys Consultores Associados S/C Ltda". The environmental and genetics effects on these traits were analyzed using the least square method applying mathematical models that included fixed effects of contemporary group (GC) and IPV, IDD, AD, AM and HI as covariates. All environmental effects included in the model showed significant influence on the evaluated traits at weaning, except for IDD on GND and AM on all traits. All traits were significantly influenced by AD and HI. These results indicated that environmental and genetic effects were important sources of variation for these traits and, consequently, they should be considered in genetic evaluations.Key Words: conformation, environmental effects, growth traits, individual heterozygosity, musculature, precocity IntroduçãoCom a competi...

Ganho De Peso E Características De Carcaça De Bovinos Nelore E Meio Sangue Angus-Nelore Em Regime De Suplementação a Pasto

“…Os animais ½ sangue do presente estudo, os quais tiveram interação positiva com a relação genética-ambiente, demonstrando resultados superiores ao grupo Nelore. Segundo Queiroz et al (2009) a genética da raça Nelore impossibilita elevados resultados pré-desmama e animais cruzados são superiores a animais puros devido a expressão da heterose.…”

<b>How the calving order of cows affects the performance of Nellore calves

“…However, according to Queiroz et al (2009), when assessing ADG, the visual scores of conformation, precocity and weaning muscle of Brangus animals, verified that cows that weaned calves with better performance were those aged between eight and 12 years old, and, from that age, there was a decrease in the performance of the calves. This fact is due to a decrease in maternal ability and low milk production as the cow ages.…”

“…However, the expression of this quantitative phenotypic characteristic is not only due to its genes, but also influenced by month of birth, the cow's gestational age, the calf's weaning age, the matrix's maturity weight, the mother's racial composition, the calf's sex, and correlations between these variables (Castro-Pereira, Alencar, & Barbosa, 2007;Bocchi, Oliveira, Ferraz, & Eler, 2008;Queiroz, Costa, Oliveira, & Fries, 2009;Barichello, Alencar, Torres Jr., & Silva, 2011;Fialho et al, 2015).…”

Genetic and environmental effects on scores of conformation, precocity and muscling in long yearling Nellore cattle

“…Conformation (C), precocity (P) and muscle (M) scores estimate the amount of meat produced if the animals were slaughtered at the time of evaluation, the animal's ability to accumulate the minimum amount of fat required for slaughtering without reaching high body weight and muscle mass present in the carcass, respectively (QUEIROZ et al, 2009). The use of scores to evaluate carcass traits in live animals was proposed by Long (1973) as an alternative to the exclusive selection by weight or weight gain, which is not enough to improve the performance and carcass quality of the animal after slaughter (QUEIROZ et al, 2009).…”

“…The use of scores to evaluate carcass traits in live animals was proposed by Long (1973) as an alternative to the exclusive selection by weight or weight gain, which is not enough to improve the performance and carcass quality of the animal after slaughter (QUEIROZ et al, 2009). …”