Estimates of repeatability and heritability of productive and reproductivetraits in a herd of Jersey cattle

Estimates of the repeatability and heritability of 19 measures of performan ce in Jersey cows were obtained using an animal model with a relationship m atrix and a derivative-free restricted maximum likelihood algorithm. The da ta consisted of 935 records for 374 cows by 69 sires over the period 1969-1 987. The estimates were similar to those obtained by ordinary least squares methods reported for the same data set and in other studies, hut had small er error variances. A likelihood ratio test showed agreement between these heritability estimates and those in the literature. The heritability estima tes of milk, fat, protein, lactose-mineral, solids-not-fat, and total solid s yields were about 0.25; for the corresponding percentages, and for the pr otein to fat and solids-not-fat to fat ratios, the estimates were 0.50. Her itability estimates were 0.10 or less for the time from parturition to firs t breeding and for three measures of somatic cell counts. These estimates o f heritability in a dairy cattle population in a subtropical environment we re not different from those of populations in temperate climates.