Genetic Relationships between Milk Yield, Somatic Cell Count, Mastitis, Milkability and Leakage in Finnish Dairy Cattle Population

Heritabilities and genetic and phenotypic correlations were estimated for subjectively scored milkability and leakage, clinically recorded mastitis, somatic cell score (SCS) and milk production using data from Finnish sire sampling program, health and milk recording system. Four sets of data were analyzed using multi-trait REML included in DMU-package with sire model. The data consisted of 23,854 Finnish Ayrshire (FAY) and 10,720 Finnish Hostein-Friesian (FHF) cows. Records of clinically recorded mastitis, SCS and milk production for three first lactation were used. Observations of milkability and leakage were collected from first calving cows. The estimated heritabilities for clinically recorded mastitis were low (0.01 0.02). The heritability estimate of leakage was 0.08. For milkability, heritability estimates were 0.24 for FAY and 0.16 for FHF. The heritabilities of SCS varied between 0.14 and 0.23. The phenotypic correlations were low (-0.11 0.29). The genetic correlations between milkability, leakage and SCS were from moderate to high positive (0.22 0.89). Genetic correlations between milkability and clinically recorded mastitis were negative or almost zero (-0.50 0.02). The genetic correlation among udder health traits was moderatly (0.31 0.49). The milkability and leakage were not genetically correlated with milk production. The clinically recorded mastitis had an antagonistic relationship with milk production (rg = 0.31 0.49). In general, these results indicate that milkability is an optimum trait, because selection for faster milking cows increases leakage and SCS and selection for slower milking cows increases clinical mastitis. In addition milkabililty is not correlated with milk production. ________________________________________________________________________________