[Continuing eco-pathological survey: 10. Variation of pathological frequency in dairy cow stock as a function of season, year and number of lactations].

The distribution of main herd diseases in course of time is studied with the season, the year and number of lactation. There is a seasonal effect for retained placenta, spring and summer being a favorable time for the increase of their frequency. Milk fever is also more frequent during summer. Out-calving pathologies are more frequent during housing time, but we do not observe any monthly variation for ovarian pathology. The age is a risk factor for milk fever and retained placenta. On the contrary, dystocia and stillbirth are more common on heifers. All the metabolic disorders and infectious diseases (mastitis-metritis) seem to be more frequent on old cows. The variations between years are interpretable with difficulty because they depend on the regularity in the quality of collected data. More, the necessity for the breeders to observe conscientiously their animals is a favouring factor for the improvement of the health status of the herd.