02193naa a2200289 a 450000100080000000500110000800800410001902400510006010000210011124501350013226000090026752012550027665000110153165000180154265000250156065000250158565300270161065300240163765300180166165300280167965300330170770000180174070000140175870000180177270000230179077300900181321334972021-12-29       2021    bl uuuu     u00u1 u    #d7 ahttp://dx.doi.org/10.1590/1678-4162-120712DOI1 aSANTOS, E. P. B.  aEstimation of genetic parameters for test-day milk yield in Girolando cows using a random regression model.h[electronic resource]  c2021  aThe objective of this study was to estimate the components of variance and genetic parameters of test-day milk yield in first lactation Girolando cows, using a random regression model. A total of 126,892 test-day milk yield (TDMY) records of 15,351 first-parity Holstein, Gyr, and Girolando breed cows were used, obtained from the Associação Brasileira dos Criadores de Girolando. To estimate the components of (co) variance, the additive genetic functions and permanent environmental covariance were estimated by random regression in three functions: Wilmink, Legendre Polynomials (third order) and Linear spline Polynomials (three knots). The Legendre polynomial function showed better fit quality. The genetic and permanent environment variances for TDMY ranged from 2.67 to 5.14 and from 9.31 to 12.04, respectively. Heritability estimates gradually increased from the beginning (0.13) to mid-lactation (0.19). The genetic correlations between the days of the control ranged from 0.37 to 1.00. The correlations of permanent environment followed the same trend as genetic correlations. The use of Legendre polynomials via random regression model can be considered as a good tool for estimating genetic parameters for test-day milk yield records.  aBovino  aGado Leiteiro  aParâmetro Genético  aVariação Genética  aCorrelação genética  aFunção de Wilmink  aHerdabilidade  aPolinômios de Legendre  aPolinômios splines lineares1 aFELTES, G. L.1 aNEGRI, R.1 aCOBUCI, J. A.1 aSILVA, M. V. G. B.  tArquivo Brasileiro de Medicina Veterinária e Zootecniagv. 73, n. 1, p. 18-24, 2021.