Estimation of covariance components for the first four lactations in Holstein cattle according to different models

Abstract

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 w as an independent univariate analysis of milk produ ction for lactation. Model II was a repeatability model where lactation was considered the repeated measurement of the same characteristic. Model III was a multivariate a nalysis in which each lactation was considered an i ndependent characteristic correlated with the rest. The progra m REMLF90 was used for the analyses. The data show that for the Holstein breed under these study conditions, th e estimation of covariance components for milk yiel d in the first four lactations are best carried out using a multivariate animal model.