ABSTRACT
The aim of this study was to estimate the (co)variance components and breeding values for birthweight (BW) in Nellore cattle by considering or not identical weights that exhibit a high frequency within the contemporary group (CG). A total of 175,258 BW records of Nellore cattle born between 2002 and 2018 were used. The CG was formed by farm, year of birth, sex and feeding regime at birth. CGs with more than 16% of identical BW values were eliminated, generating a data file called BWd. Another file was created without removing these animals (BWt). A mixed linear model was used for statistical analysis, which included fixed and random effects. In both data files analysed, single-trait analysis was performed by Bayesian inference. The mean direct and maternal heritability for BW and the correlation between direct and maternal effects were 0.27, 0.07 and -0.07 for BWt, respectively, and 0.30, 0.093 and -0.07 for BWd. This method should affect the estimation of genetic merits of animals for BW, providing greater safety in the choice of sires.
Subject(s)
Birth Weight/genetics , Cattle/genetics , Animals , Bayes Theorem , Brazil , Breeding , Data Accuracy , Diet/veterinary , Female , Linear Models , Male , Maternal InheritanceABSTRACT
Dados de pesos aos 205 (P205) e 365 (P365) dias de idade, de 28.946 animais Tabapuã, provenientes de 152 fazendas dos diversos estados brasileiros, nascidos no período de 1976 a 1995, foram utilizados nesta análise. Foram avaliadas as interações genótipo-ambiente, bem como estimadas herdabilidades direta e materna pelo método de máxima verossimilhança restrita em modelo estatístico, que incluiu efeitos fixos de grupo contemporâneo, idade da vaca ao parto (covariável) e efeitos aleatórios genéticos direto e materno. As estimativas de herdabilidade direta e materna para P205 nas regiões Sul (R1), Sudeste (R2), Centro-Oeste (R3) e Nordeste (R4) foram: 0,02 e 0,31 (R1), 0,17 e 0,19 (R2), 0,20 e 0,09 (R3) e 0,06 e 0,16 (R4). Para P365, foram 0,05 e 0,03 (R1), 0,20 e 0,03 (R2), 0,51 e 0,62 (R3) e 0,15 e 0,05 (R4). As correlações genéticas encontradas para as características P205 e P365, ambas consideradas características distintas nas regiões R1, R2, R3 e R4, foram: 1,00 e 0,99, 0,84 e 0,99, -0,86 e 0,73, 0,98 e 0,93, 0,51 e 0,45, 1,00 e 0,12 para R1/R2, R1/R3, R1/R4, R2/R3, R2/R4 e R3/R4, respectivamente. Esses resultados indicam que, na desmama (P205), o efeito da interação genótipo x ambiente foi observado somente nas combinações que envolveram a região Nordeste (R4) e as regiões Sul (R1) e Sudeste (R2). Para pesos pós-desmama (P365), o efeito dessa interação foi evidenciado em todas as combinações que incluíram a região Nordeste.(AU)
Body weight records at 205 (205BW) and 365 (365BW) days of age of 28,946 Tabapuã animals born during the 1976-1995 period from 152 Tabapuã herds of several states of Brazil, were used to evaluate genotype by environment interactions and to estimate genetic and maternal heritability by restricted maximum likelihood methodology. The statistical model included the fixed effects of contemporary group and age of cow (covariate), and the random additive genetic and maternal effects. Maternal and genetic heritability estimates for BW205 considered as different traits in each of the South (R1), Southeast (R2), Central West (R3), Northeast (R4) regions were .02 and .31, .17 and .19, .20 and .09 and .06 and .16, respectively, and for BW365 they were .05 and .03 (R1), .20 and .03 (R2), .51 and .62 (R3) and .15 and .05 (R4). The genetic correlation for 205BW and 365BW both considered as different traits in each of the South (R1), Southeast (R2), Central West (R3), Northeast (R4) regions were, respectively, 1.00 and .99, .84 and .99, -.86 and .73, .98 and .93, .51 and .45, 1.00 and .12 for BW205 and BW365 in R1/R2, R1/R3, R1/R4, R2/R3, R2/R4 e R3/R4, respectively, indicating a significant genotype by environment interaction for 205BW only for the combination between Northeast and the South and Southeast regions. For the 365BW there was a significant genotype by environment interaction for all combinations involving the Northeast region.(AU)