Evaluation of body weight and hip height in Nellore cows in a tropical environment

• Published in: Livestock science Vol. 233; p. 103953
• Main Authors: Portes, Juliana Varchaki, Cyrillo, Joslaine Noely dos Santos Gonçalves, Faro, Lenira El, Mercadante, Maria Eugênia Zerlotti, Teixeira, Rodrigo de Almeida, Dias, Laila Talarito
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2020
• Subjects: Beef cattle; Heritability; Longitudinal data, Mature size; Beef cattle; Heritability; Longitudinal data, Mature size
• ISSN: 1871-1413; 1878-0490
• DOI: 10.1016/j.livsci.2020.103953

•It is essential to model the heterogeneity of residual variance when studying body weight in Nelore cows, but not for hip height, which can be properly modeled by assuming a homogeneous residual variance.•A model with Legendre polynomials of order k = 3,6 for the direct additive genetic and animal permanent environmental effects, respectively, and a linear polynomial for the maternal permanent environmental effect is suitable to model body weight in Nelore cows.•A model with Legendre polynomials of order k = 4,3 for the direct additive genetic and animal permanent environmental effects, respectively, is sufficient to model hip height in Nelore cows.•The high heritability and correlations estimates between weights and hip height at different ages suggest the selection on these traits results in genetic gain and can be used to monitor the adult size of the animals. The aim of this study was to evaluate random regression models to estimate genetic parameters for body weight and hip height in Nellore females and identify the best time to select these characteristics for adult size control. The dataset comprised 33,569 body weight and 31,804 height records from 3,860 and 3,487 females, respectively. Contemporary group and physiological state (for body weight analysis) were modeled as fixed effects, whereas age at birth (both linear and quadratic effects) and Legendre polynomials of age at (k = 4) as covariates. Random effects, including the additive genetic effects, and the animal permanent environment effect and the dam (for body weight analysis), were also included in the model. Random effects were modeled by Legendre polynomials of degree k in [3, 6], while residues were considered to be homogeneous or heterogeneous. The best model for body weight included heterogeneous residual variance with 21 classes and Legendre polynomials of degree k = 3, k = 6 and k = 1 for the additive genetic effects, animal and maternal permanent environment effects, respectively. The best model for hip height included homogeneous residual variance and Legendre polynomials of degree k = 4 and k = 3 for the additive genetic effects and animal permanent environment effect, respectively. Heritability estimates were moderate to high and suggest the studied characteristics could be used for maintaining cow size, being the selection at 3 years sufficient to get the desired size.