Evaluation of alternative schemes for recording body weights in meat-type quails by using random regression

Abstract

ABSTRACT. Data from 8759 meat-type quails from the UFV1 strain and 9128 from the UFV2 strain were used to assess the possibility of reducing the number of body weight records in genetic evaluations. The evaluated animals were weighed weekly since hatching to the 6th week of life, with up to 7 records of body weight for each bird. The data were evaluated by random regression models, with 9 alternative schemes of data recording, which included 4 records for each scheme and their covariance functions for additive and permanent environmental effects of order 3, fitting 4 intervals for residual variance, and a complete scheme, with 7 records, order of fit 6 for additive and permanent environmental effects and 7 intervals for residual variance. Estimates of heritability for body weight at the 6th week varied from 0.45 to 0.53 for the UFV1 strain and from 0.28 to 0.54 for UFV2 strain. The schemes that had more records in points at the final extreme of the age range showed better estimates, which was likely due to certain properties of polynomial regression that led to biased results in the final extreme of the age range when data are unbalanced. The reduction of the number of body weight records taken during the growth phase is feasible, with little change to breeding value estimates, when 4 body weight records are used in random regression models.

Modelos de regressão aleatória na seleção de codornas de corte para produção de ovos

“…Resultados semelhantes foram obtidos por Silva et al (2013), que estudaram o MRA quanto à produção de ovos em codornas e verificaram que a utilização de um modelo com 21 parâmetros e com os polinômios de Legendre de ordem três, para modelar a trajetória fixa, e de ordem quatro, para modelar as trajetórias aleatórias, proporcionaram melhor ajuste quanto à produção de ovos. Teixeira et al (2012) verificaram que o modelo com 33 parâmetros, com K a = 5, para os efeitos genéticos aditivos diretos, e K c = 5, para o ambiente permanente de animal, proporcionou um melhor ajuste para modelar a trajetória de crescimento de codornas de corte do grupo genético UFV1.…”