Estimation of genetic parameters for test-day milk yield in Girolando cows using a random regression model

ABSTRACT The objective of this study was to estimate the components variance and genetic parameters test-day milk yield in first lactation Girolando cows, using a random regression model. A total 126,892 (TDMY) records 15,351 first-parity Holstein, Gyr, breed cows were used, obtained from Associação Brasileira dos Criadores de Girolando. To (co) variance, additive functions permanent environmental covariance estimated by three functions: Wilmink, Legendre Polynomials (third order) Linear spline (three knots). polynomial function showed better fit quality. environment variances for TDMY ranged 2.67 5.14 9.31 12.04, respectively. Heritability estimates gradually increased beginning (0.13) mid-lactation (0.19). correlations between days control 0.37 1.00. followed same trend as correlations. use polynomials via model can be considered good tool estimating records.