Genetic parameters of somatic cell score and lactose content in goat’s milk

The aim of the study was to estimate the heritability and repeatability of somatic cell score (SCS) and lactose content, and also the genetic correlation between those and other dairy production traits. Milk yield, fat, protein and lactose content, and somatic cell count were recorded once a month for 11 years in a single herd, resulting in 4 417 records from 282 does. The number of animals in pedigree was 11 659. An animal multiple-trait model accounted for breed, day of milking (Legendre polynomial regression on standardized days-in-milk), year of birth, year of milking, kidding season, litter size and parity. Variance components were estimated with the REML method using the DMU software. The highest content of lactose was found in the milk of primiparous goats which gave birth to one kid. The youngest goats had the lowest SCS. The heritabilities for SCS and lactose content were 0.21 and 0.27, while repeatabilities were 0.31 and 0.55, respectively. The genetic correlation between milk yield and lactose content was -0.46, while between milk yield and SCS was 0.59. The genetic correlations between lactose content and fat and protein contents were 0.62 and 0.54, respectively. No correlations between SCS and protein, fat and lactose contents were found. Lactose content and SCS in goat’s milk proved to be highly heritable which facilitates efficient inclusion of these traits in the breeding objective.