Components of (co)variance of the days open in Siboney dairy cows

Abstract

The records of 63,406 calvings of Siboney dairy cows (5/8 Holstein 3/8 Cuban Zebu) were used to estimate the components of covariance of the days open (DO). Five models were used: of repeatability; univariate; bivariate; of random regression with Legendre polynomials and the parity number as predicting variable; and a model of random regression with Legendre polynomials and heterogeneity of the residual variance. The heritability obtained with the univariate model was 0.09 in the first calving and decreased to 0.05 in the fifth. A higher estimate of heritability (0.12) was obtained with the repeatability model. When the model of random regression with heterogeneity of the residual variance was used, the heritability was higher than the values estimated with the previous models. The genetic correlations among the DO in different calvings, estimated with the models of random regression with and without heterogeneity of the residual variance, were close to 1.0. It is concluded that the estimates of heritability increased with the use of the random regression models. The genetic correlations among the DO of different calvings indicated that in the first three, the DO are regulated for the most part by the same genes. Keywords

Eigenvector index for two female fertility traits based in random regression coefficients matrix in Holstein cows

“…Menéndez-Buxadera et al (2013) also found that the quadratic Legendre polynomial provided a better fit than the linear polynomial when analyzing DO and other fertility traits in the Holstein cattle population of Spain. In other studies dealing with fertility traits analyzed with random regressions, Nishida et al (2006) used a quadratic polynomial for NSC in one herd of Japanese black cattle and Gutierrez (2010) and González-Peña et al (2010) employed a linear polynomial for an experimental US Holstein cattle and for Siboney dairy cattle in Cuba. Because the quadratic fit was the model with the best goodness of fit, results for the covariance functions and eigendecomposition are only shown for this model.…”