Análisis productivo y reproductivo de vacas lecheras Holstein, Pardo Suizo y sus cruzas en un sistema a pastoreo

Abstract

This work aims to conduct a comparative analysis of productive and reproductive aspects of cows belonging to three dairy genotypes, in a grazing system with supplement in Entre Ríos, Argentina. Retrospective data were analyzed for the 2007-2013 period considering lactations of primiparous and multiparous cows from two dairy breeds and their first crosses: Holstein (H), Brown Swiss (P) and F1 (Brown Swiss cows x Holstein bulls). Primiparous cows had different birth weights considering genotype, but multiparous did not. The age at first calving was lower for F1 cows compared to H, without difference with P. F1 was the genotype with lowest birth-conception interval (ipc) while P showed the highest. The number of services per pregnancy and lactation days accompanied ipc trend, with high variability within each genotype. Milk production was above 6,000 liters in primiparous and over 7,000 liters in multiparous, achieving the genotype H 8,207 liters. Productions of butirose fat, total protein and total solids were very similar among genotypes. For this system and the considered lactations, the variations among each genotype do not allow to adequately explain the response to the environment and managing system, although at the first birth H cows were higher and heavier and produced more milk, while F1 in the first lactation showed better reproductive response, with similar fat, protein and total solids to those of pure breed. For this system it can be stated that F1 cows have an acceptable milk production, specially considering total solids, with better reproductive responses. It is necessary to analyze information about higher number of lactations and / or animals to select adequately the genotypes better adapted to this environment and productive system.