COMPONENTS OF THE DIET IN THE DRY PERIOD AS RISK-FACTORS FOR PLACENTAL RETENTION IN FRENCH DAIRY HERDS

A survey was conducted from July 1978 to June 1982 in six French regions with farmers and practising veterinarians (79 herds were surveyed for two to four years). Two groups of dairy herds were made up according to their placental retention incidence rate (PRI). The first group included the 10% of the herd-years with the highest PRI (PR + group, n = 24); the second one included the 24 herd-years with the lowest PRI that also matched according to the region and the period. The data concerned: number of feeding days for 13 feedstuffs given to cows during the dry period, six periparturient disease incidences, milk yield, calving number and herd size. Data were retrieved from a database and analysed using barycentric discriminant analysis to find the variables discriminating PR- and PR+ herds. PR+ herds were characterised by a shorter duration of concentrates and a longer one of grass silage feeding compared with PR- herds. These two variables explained 62.7% of the variation. The remaining 22 variables each explained less than 10% of the variation. A high linolenic/linoleic acids ratio in diets, including grass silage without concentrates offered to dry cows, could result in a lack of PgF2α and explain the high PRI in PR+ herds. Such diets could also lead to placental retention through energy deficiency. The relevance of these factors to the etiology of placental retention is discussed. © 1990.