Body condition score, health, yield and fertility in diary cows.

The effects of body condition score at drying off and after calving and the rate of loss of body condition score during the dry period on the performance of 2162 cows in eight commercial Israeli Holstein herds were evaluated. The relationships between health, fertility and yield and body condition score were examined by using multiple logistic regressions for measurements with only two outcomes and general linear models for the continuous variables. Herds, parity, season, length of dry period, postparturient diseases, twinning, stillbirth, induction of calving and high somatic cell counts were used as confounding and other exposure variables. Multiparous cows that were underconditioned at calving were culled and exhibited more postparturient uterine diseases. The risk of retained placenta was greater for cows that were underconditioned at drying off, whereas cows that lost more body condition during the dry period suffered more from both retained placenta and metritis; the two effects being independent of each other. An apparent increase in the risk of ketosis associated with over-conditioning at calving could be partly attributed to long dry periods. Cows with a higher condition score at calving were less prone to anoestrus but did not conceive more successfully to first service. A reduction of six open days in primiparous cows was estimated for each additional unit of body condition score at calving. Multiparous cows that lost more body condition during the dry period suffered more from inactive ovaries and were more likely to be open 150 days after calving in the next lactation. Cows calving in a higher body condition score produced more milk, fat and protein in the first 90 days of lactation, the effect being most pronounced on milk fat content.