Genetic evaluation of selected Holstein population with an animal model for milk production

Milk production of Holstein cow records were examined. Final data consisted of records for 8 331 lactations of 3 830 Holstein cows in 137 herds. Breeding values were obtained with an animal model including herd-year-season, calving numbers, age classes and duration of lactation as fixed effects and additive genetic and permanent environmental random effects. Average annual milk production was 4 335.79 kg (s = 1 203.11) with average length of lactation 294 days. The breeding values ranged from -965.67 to 1 469.17 with average value 4.40. The accuracy ranged from 47.15 to 99.71%. The average breeding value of males was 46.54 (s = 168.30) and females 1.11 (s = 192.10). The annual genetic trend from 1983 to 1991 estimated by regression coefficient of individual breeding values on year of birth was + 10 kg per year (P less than or equal to 0.0001). The environmental trend was negative and highly significant (b = - 98 kg per year). Heritability of milk production was 0.19 and repeatability 0.34.