Repeatability and heritability of lactational occurrence of reproductive disorders in dairy cows

Abstract

The repeatability and heritability of reproductive disorders were estimated using data from 28 277 Finnish Ayrshire cows. A four-trait linear model including effects of community-year, calving age and month, birth year of the sire, and random sire was used. The number of sires was 339. Variance components were estimated using a method of restricted maximum likelihood. The disease traits were analyzed also with a categorical model including the same effects except that community and year were included as two separate factors. Variance components were estimated with the method of marginal maximum likelihood. Genetic relationships between sires were included in both models. The phenotypic correlation between the first and second lactation was defined as a repeatability of the trait. The lactational incidence risk of reproductive disorders was 0.16 in the first lactation and 0.15 in the second. The risk of ovulatory disorder (anestrus and subestrus, 41%; cyst, 46%; other infertility, 13%) and metritis (early, 63%; late, 37%) were 0.13 and 0.04 in the first lactation and 0.13 and 0.03 in the second lactation, respectively. Average milk production was 4956 (6095 as 3.5% fat corrected milk (FCM)) kg in the first and 5547 (6805 as 3.5% FCM) kg in the second lactation. Estimates of heritabilities in the first lactation were 0.03 and 0.04 (0.03 and 0.02 in the second lactation) for ovulatory disorder and for metritis, respectively. Genetic correlations between the first and the second lactation recordings were 0.60 for ovulatory disorder, −0.58 for metritis and 0.94 for milk yield. Repeatabilities between subsequent lactations were 0.33 for ovulatory disorder, 0.24 for metritis, and 0.67 for milk yield. In the first lactation, the genetic relationship between milk yield and ovulatory disorder and between milk yield and metritis were large and unfavorable. Also in the second lactation, the genetic correlation between milk yield and ovulatory disorder was large, but the correlation between milk yield and metritis was zero.