Failure of 25-hydroxycholecalciferol to prevent milk fever in dairy cows

An intramuscular injection of 4 mg of 25-hydroxycholecalciferol [25(OH)D 3 ] in corn oil was administered 3-10 days before calving to 123 cows of third or subsequent lactation on 6 dairy farms. There were no significant differences in the prevalence and severity of milk fever or in the level of plasma calcium within 24 h of calving between the injected cows and paired control animals. Cows with milk fever were significantly older than those without, but were no different in circulating 25(OH)D 3 levels or in condition score. The prevalence of milk fever in the selected cows in each herd ranged from 0 to 26% and was correlated with the calcium content of the hay supplement fed prior to parturition.