[Continuous ecopathological survey. 2. Typology of dairy cattle farms with high and low fertility]

Management characteristics were analysed in two groups of dairy herds (20 to 60 cows per herd) during a continuous eco-pathological survey, in relation to high and low fertility. 59.8% of the cows from the eleven high fertility herds were successfully inseminated at first service and 11.4% of the cows inseminated for the first time more than 40 days post-partum required 3 or more services. The corresponding values were 51.1 and 25.6% for the ten low fertility herds. Other reproductive criteria (calving-first service interval, disturbed oestrus cycles), which more depend on the reproduction management, were not different between the two groups. Feeding system greatly varied in the low fertility group. Frequent changes in diet composition, a longer period of "green" forages distribution (crucifers, grass silage) as well as less utilisation of concentrates are some of the reasons which can explain the low fertility. Calving occurred mainly from February to April in low fertility herds, at the transition from winter diets to grazing. Milk production was lower, 4 580 kg per cow and per year vs 5 520 kg for high fertility group. Milk production falls were more frequent and Holstein semen was less used. Tied housing conditions, and higher incidence of Fasciola hepatica and abomasal mematodes characterised low fertility herds; inversely, the clinical pathology appeared to be less frequent in this group. Soil manganese concentration was lower (16.3 ppm) in the low fertility group as compared to the other group (30.9 ppm); this could be explained by less schistose rocks where the low fertility farms are localized. In conclusion, the risk factors associated with low fertility may be attributed to: the composite system of feeding in addition to the use of "green" forages, a lack of proper programming with regards to the season of calving, and the high frequency of parasitic infestations, with special reference to liver fluke.