INFLUENCE OF HAY TYPE ON DAIRY-COWS PERFO RMANCE

Data from 27 dairy cows (Abundance breed) in a 2-yr experiment were us ed to examine the fill value of different hays from native mountain gr assland (northern alps) and the modifications in the cows' performance when the type of hay was changed. Cows were fed ad libitum with 8 dif ferent types of hay (table I). The amount of concentrate was adjusted to meet the nutritive requirements and was not modified when the type of hay was changed. Fill values of the different types of hay calculat ed from cows' performance varied between 0.96 and 1.21 UEL/kg DM. Thes e values were lower than those of other natural grassland hays (lowlan d or upland) with the same energy value (fig 1). Immediate variations in milk production (-1.8 to + 1.0 kg/d) and protein content (-1.9 to 1.6 g/kg) when the type of hay was changed were higher than fat conte nt variations (-1.0 to + 1.4 g/kg) (fig 2). After 1 or 2 wk adaptation , these variations in performance from one type of hay to another were low. Protein content variations were significantly related to corresp onding energy supply variations (R = 0.80, P < 0.05) (fig 3). Netherth eless, some types of hay seem to have a specific effect on milk produc tion or milk composition. These results have to be confirmed on a larg er range of hay types.