[Descriptive epidemiology of placental retention in intensive dairy herds in Brittany].

The influences of several risk factors (temporal, mechanical, zootechnical and nutritional) on the incidence of placental retention (PR) were tested. The study was conducted in Brittany on 5,240 calvings of Black-Pied females belonging to 47 herds surveyed over a period of four consecutive years. For twin births, the PR-incidence levels were only decreased in the case of calves born alive. Single calvings were associated with PR after more than three artificial inseminations, or when stillbirths, dystocia or shortened gestational periods were observed, but the frequency varied in relation to calving rank. Increased total amounts of concentrate and cake supplied at the end of the gestational period decreased the incidence of PR in heifers. Shorter dry periods and high levels of milk production increased the risk of PR in multiparous cows. The frequency at which PR was observed in both cows and heifers was lower in autumn. Milk production and fertility were decreased in animals having experienced PR. In addition, they were subject to more uterine disorders than other cows during the subsequent lactation, whatever number of calves had been carried. Milk fever in the third lactation and metabolic diseases in the fourth were more frequently observed following PR.