Análise das relações da curva de crescimento e eficiência produtiva de vacas da raça Holandesa

Abstract

The objective of this study was to analyze the relationships between previously estimated individual growth curve parameters (mature weight and maturing rate) and measures of productive efficiency of 333 Holstein-Friesian cows, born from 1992 to 2002. Data on age at first calving, first lactation milk yield, first lactation length, first calving interval and milk yield per day of first calving interval were analyzed using a generalized linear model with the fixed effect for age group (year-season of birth), the random effects of sire and error and the linear and quadratic effects of mature weight and maturing rate. In the analyses of longevity and productive life, the fixed effect of culling reason was also included in the model. There were significant linear and quadratic effects of maturing rate on most of the traits analyzed, except on first calving interval and milk yield per day of first calving interval. The estimates of optimum maturing rates varied from 0.0896 to 0.1187 kg/ kg of liveweight/month. There were both linear and quadratic effects of mature weight on longevity. The optimum combination was a mature weight of 701 kg and a maturing rate of 0.0934 kg/kg of liveweight/month. Mature weight showed a significant and unfavourable correlation with first lactation length (-0.11). Significant correlation coefficients were obtained between maturing rate and age at first calving (-0.22), first lactation milk yield (0.18), first lactation length (0.18) and longevity (0.14), confirming the hypothesis that cows with faster maturing rates have higher productive efficiency. © 2009 Sociedade Brasileira de Zootecnia.