Factores que afectan la curva de lactancia de vacas Bos taurus x Bos indicus en un sistema de doble propósito en el trópico húmedo de Tabasco, México

Abstract

The objectives were to describe the lactation curves of Holstein x Zebu (HZ) and Holstein x Sahiwal (HS) cows in a dual-purpose cattle system in Tabasco, Mexico, to determine the effect of some environmental factors on the parameters of the lactation curves and to estimate their repeatabilities (re). The parameters of the lactation curve: a=milk production at the beginning of lactation, b=slope of the lactation curve up to the peak of milk production (PMP) and c=slope after the PMP, were estimated using the Wood model. The coefficient a and the PMP were influenced for all the factors studied and the persistency of production by year and season of calving. The coefficients b and c were influenced by year of calving. The coefficients a, b and c for the lactations of the HC and HS cows were: 7.49, 0.178 and 0.0037 and 6.70, 0.196 and 0.0036, respectively. Cows calving en the wet season had lower PMP values than those calving in the dry or rainy seasons. First parity cows had lower a and PMP values than cows with two or more lactations. The moderate re values of a (0.35), PMP (0.42) and their phenotypic correlation with milk yield during the whole lactation, suggest that they can be used as criteria for culling cows.