Resumo

PALACIOS ESPINOSA, Alejandro et al. Estimation of covariance components for the first four lactations in Holstein cattle according to different models. Zootecnia Trop. [online]. 2007, vol.25, n.1, pp.9-17. ISSN 0798-7269.

Milk production of Cuban Holstein cows was analyzed. There were 15415 lactation records of 9382 cows, which gave birth to the calves of 482 sires. Three models were established to study the milk production for 305 days during each of the first four lactations. Model I was an independent univariate analysis of milk production for lactation. Model II was a repeatability model where lactation was considered the repeated measurement of the same characteristic. Model III was a multivariate analysis in which each lactation was considered an independent characteristic correlated with the rest. The program REMLF90 was used for the analyses. The data show that for the Holstein breed under these study conditions, the estimation of covariance components for milk yield in the first four lactations are best carried out using a multivariate animal model.

Palavras-chave : covariance; heritability; correlations; Cuban Holstein.