Valorisation des rations alimentaires dans les troupeaux laitiers : états des lieux et facteurs explicatifs des différences entre production théorique et production observée

The observations in the field show that milk production of dairy herds is consistent with the composition of the rations distributed, but that there is nevertheless a high degree of variability between farms. In order to understand this variability, French (Avenir Conseil Elevage) and Belgian (Inagro) datasets, set up within the INTERREG PROTECOW project, were used (n = 1604). These datasets contain data on milk production (production and contents) in relation to diets distributed (centesimal composition) in the French-Belgian crossborder area. The use efficiency of the diet was calculated as the ratio between the observed milk production and the expected milk production, estimated according to the composition of the distributed ration. A principal component analysis completed by clustering was used to create four homogeneous groups. Each group differed from the others in terms of milk production level, milk composition (fat and protein contents), type of diet (proportions of forages, concentrates, type of forages) and its use efficiency, the latter being different between each group (P < 0,001). Thus, the first group was characterised by silage maize rations, the second by milk production based on concentrates, the third by rations based on pasture and the fourth by mixed rations. While the use efficiency of the diet reached 120,0% in the silage maize group, it varied from 85,3% to 95,0% in the other three groups. The analysis of the productions observed in practical conditions shows that there is room for improvement in the adaptation and utilisation of dairy cow diets and that, based on the current feeding system, the type of ration has an influence on the observed vs expected milk production ratio.