INCREASED PERINATAL FRENCH DAIRY CALF MORTALITY ASSOCIATED WITH FRESH RAPE IN THE PREPARTUM DIET

Seventy-nine French dairy herds were surveyed over 2-4 years. Two groups of herd-years were made up according to their perinatal calf mortality rate (PCMR) in order to detect risk factors for the disease in the prepartum diet of the dams. The first group included the 10% of the herd-years with the highest PCMR (PCM+ group, n = 24). The second group included the 24 herd-years with the lowest PCM (PCM- group) and with the same number of herd-years for each region and each annual period. The herd data concerned: seven disease incidences in the cows, herd size, breed, housing system, milk yield and composition, calving number, calving season, dry period length, number of feeding days for 15 feedstuffs given to cows during the last 90 days of gestation and administration of vitamins A, D and E to pregnant dams. Data were analysed using a barycentric discriminant analysis to find the variables which discriminate between PCM- and PCM+ herd-years. PCM+ herd-years were characterised by longer durations of feeding cows with fresh rape (Brassica napus) during the late gestation period and by higher difficult calving incidences. These two variables explained 43% of the total variation. None of the remaining 27 variables explained more than 10% of the variation. The relevance of the nutritional risk factor (B. napus forage in the precalving diet) to the actiology of perinatal mortality in the calf is discussed with reference to potential antithyroid and hepatotoxic effects of rape.