INFLUENCE OF INCREASING LEVEL OF CONCENTR ATE ON THE CHEWING TIME OF THE RATION IN DAIRY-COW

Four different diets, made up of a grass silage and four concentrate s upplies (0, 3, 6, 9 kg) were fed, in a latin square design, to eight d airy cows. Average dry matter (DM) intake of the animals was 14.5 kg f or silage and 3.9 kg for concentrate. Animals had a live weight of 636 kg and their production was 15.8 kg fat-corrected milk. The total tim e of chewing was not significantly different between the treatments (a verage 940 min/day). After calculation, it possible to estimate the un itary chewing time of concentrate to 10 min/kg DM and that of forage t o 62.5 min/kg DM; this last value is not influenced by the proportion of concentrate in the diet. This trial confirm that, for proportions o f concentrate under 40%, the unitary chewing time of forage can be con sidered as constant.