EFECTO DE INCORPORAR LA RAZA JERSEY A TRAVES DE CRUZAMIENTOS SOBRE PRODUCCIÓN Y COMPOSICIÓN DE LECHE

Abstract

Effect of incorporating the Jersey breed through crossbreeding on milk production and composition.
A total of 523 lactations of three genotype categories were compared: 0, 50 and 75% Jersey. Black and White or Red and White Friesian cows were indistinctly used as control group, after the similarity between the two breeds types in the population was determined statistically (P> 0.05). Lactation length was standardized to 305 days and comparisons were made among cows with the same number of calvings and calving period. Lactation milk production was 11.5% and 6.3% (avg. 8.3%) greater in Friesians compared to 50% and 75% Jersey groups, respectively, however, no differences were found among groups in terms of milk production (corrected to 4% fat)0. Lactation outputs of milk fat and milk energy were greater in crossbreds compared to the controls with no difference between crossbred groups; the protein yield however, was greater in the 75% Jersey group (P< 0.05). Differences were greater in terms of milk composition than in yield of milk or its components. Jersey crossbreds produced on average 13% more milk fat, however milk fat content was 27% higher. Similarly, differences in yield and concentration of both protein and energy for 50% Jerseys and 75% Jerseys with respect to Friesians, were: 5.2%, 16.2% and 4.1%, 15.5%, respectively. Considering the existing differences in terms of feeding, management and environment among farms, the results show the strong influence of genetic component on milk output and composition.