112. Genetic and environmental influences on maternal calving difficulty in South African Holstein cattle

Abstract

Calving difficulty is an important trait in dairy production, as it affects profitability and animal welfare. Environmental factors and genetic parameters on maternal calving difficulty (MCD) were estimated for South African Holstein cattle using data from the National Milk Recording Scheme. The original data set comprised of calving records of 10,495,603 of cows 192,052, in 14 herds that calved between 1949 and 2018. Environmental effects were tested by the General Linear Models (GLM) procedure of the Statistical Analysis System. Maternal heritability for calving difficulty in the first three lactations was estimated by the ASReml software, using linear animal and repeatability animal models. Sex of calf, parity, herd-year-season and age of dam at calving had significant effects (P <0.05) on MCD. Heritability estimates for MCD were low, ranging from 0.04±0.09 in second parity to 0.12±0.10 in third parity. Both estimates of heritability and repeatability of MCD across parities were the same in magnitude (0.04±0.04). Despite the low heritability estimates, these results provide the basis for developing genetic prediction models for MCD in South African Holstein cattle.