Factors Affecting Body Weight and Its Association with Milk Production Traits in Finnish Ayrshire and Friesian Cows

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Abstract
Data from the Finnish milk recording system consisting of records for the first three parities from a total of 66 554 Ayrshire and 9664 Friesian cows were analysed using REML methodology and sire model. Factors with statistically significant effects on body weight were: year, age and season of calving and lactation stage. The influence of the random herd effect was also evident. Within-herd herit-abilities for body weight in the first three parities were from 0.29 to 0.41 in Ayrshires and from 0.21 to 0.34 in Friesians. Genetic correlations between body weight and 305-day milk, fat and protein yields varied from +0.09 to +0.34 in the Ayrshire data and from -0.06 to +0.28 in the Friesian. Phenotypic correlations were slightly larger and positive in both breeds. Genetic correlations between body weight and fat and protein percentages were negative and phenotypic correlations were near zero.