Curvas de lactação em cabras Saanen, Alpinas e cruzadas

Mestrado em Engenharia Zootécnica - Produção Animal - Instituto Superior de Agronomia / Faculdade de Medicina VeterináriaMilk yield records from 3993 lactations by 1948 goats of the Alpine and Saanen breeds, as well as their crosses were used in this study. Different productive traits (total milk yield, daily milk yield, yield up to 305 days of lactation and lactation length) and reproductive traits (age at first kidding and prolificacy) were analyzed as a function of different factors that affect milk production, such as year and season of kidding, breed, lactation number and litter size. All the factors had a significant effect on the productive and reproductive traits, including the interaction between breed and number of lactation, such that Saanen goats had the highest yield in the first lactation and dropped afterwards, while in the Alpine breed the reduction in milk yield was only observed in the fourth lactation. Crossbred goats had better results for all traits except prolificacy, with an estimated heterosis of 5 to 8% for milk production. Lactation curves were estimated with grafted polynomials (splines) as a function of the different factors studied. The estimated curves showed a good adjustment and their variability with the levels of the different factors studied was small