Critères de constitution des lots de vaches dans des troupeaux bovins allaitants Limousins et Charolais

Abstract

In beef cattle herds, the reproductive cows are assigned to different batches, which are modified troughout the year. The only rule available to manage batches concern the calving period, during winter. The rule is that cows have to be assigned to batches according to their physiological state. The diet is then offered to fit the average nutrient requirement level in each batch. The analysis of surveys performed in 81 farms (Limousine and Charoalais areas) showed that 11 different criteria are used by farmers to assign cows to the different batches: calving date, genetic, culling, age of cows, sex of calves, " quality " of cows, weaning, batch’ size and a last category for " miscellaneous ". The number of batches have been studied according to the season, with respect to the number of criteria used suimultaneously. The physiological state of the cows is the main batching criterion only for wintering, but this concerns less than one quarter of the total number of batches identified throughout the year. The turn-out-tograss is the period involving most criteria. When several criteria are used simultaneously, the duration of batches is twice as when only one criterion is used. In the latter case, batches are uselly modified during the grazing period.