[Mortality of dairy cows in an ecopathologic survey in Brittany]

Although rare, natural death in dairy cows represents a serious economical loss. In a sample of intensive dairy farms, the mean yearly mortality rate was estimated to be 0.96%. There were various causes known (metabolic, accidental, calving-related, respiratory) and unknown (1/3 of the cases). No significant annual or seasonal variation was observed, although the beginning of the grazing period seemed to be associated with a higher mortality rate. The cows with a parity of 7 or more had a higher probability of dying (mortality rate: 3.5%). The post-partum period was also associated with a higher number of deaths. The inter-herd variability was significant, with mortality rates running between 0 and 4.24%. Nutritional diseases, digestive disorders and trauma were predisposing factors of natural death.