Genetic analysis of body condition score in the Israeli Holstein dairy cattle population

The objectives of the current study were to estimate genetic parameters of BCS as a function of lactation stage to investigate the genetic relationship between BCS, metabolic disease traits, and other traits under selection in Israel, as well as to consider the consequence of inclusion of some measure of BCS in the Israeli breeding index. The basic dataset included records on 236,350 Israeli Holstein cows with at least 1 BCS record during first parity. Heritabilities in parities 1 to 3 for BCS near calving, peak milk production, and drying-off ranged from 0.27 to 0.36 and were highest for second parity. All coefficients of genetic correlations within parities were >0.7. All coefficients of genetic correlations between parities were >0.65. Heritability was 0.45 for the mean BCS near calving, at peak milk production, and near drying-off. Heritabilities for 5 metabolic disease traits (left displaced abomasum, milk fever, ketosis, metritis, and retained placenta), dystocia, and twinning rate were all <0.1. The highest h² was for metritis in first parity, at 0.07. High BCS near calving and at peak were genetically correlated with lower incidences of milk fever, metritis, and retained placenta. These correlations were consistent across the first 3 parities. The coefficient of genetic correlation with the largest absolute value between BCS and disease traits was that for the correlation between BCS at peak production and retained placenta in first parity, at -0.39. Based on the genetic correlations between BCS and the traits included in the breeding index, inclusion of BCS in the index should result in lower genetic gain for milk, fat, and protein production and slight economic gains for female fertility, SCS, and herd-life.