INTAKE, RUMEN VOLUME, RETENTION TIME AND DIGESTIBILITY OF DIETS BASED ON POULTRY LITTER AND WHEAT-STRAW IN BEEF-COWS BEFORE AND AFTER CALVING

Beef cows in the 14 weeks before calving and during the first 12 weeks after calving were fed one of three diets based on 15, 30 and 45 % broilers poultry litter (PL), 20 % maize grain (MG) and 65, 50 and 35 % wheat straw (WS) on a DM basis, respectively. They were housed from June to November in individual open pens. Four weeks before and 9 weeks after calving, in vivo digestibility, fibre and fluid mean retention time (MRT) were measured. The intake of all diets before calving was low. Nine weeks after calving the intake of DM increased 2.1 times on the 15 % PL diet, and 1.6 times on the two other diets. The in vivo digestibility of the 15 % PL diets was lower than that of the two other diets before calving, and increased after calving, in spite of the doubling of its intake, while that of the 45 % PL diet decreased. The mean retention time of fibre in the digestive tract was not affected by the increase in DM intake after calving on the 15 % PL diet and was shortened on the two other diets. It seems that the combination of the volume taken up by the gravid uterus and the bulkiness of the 15 % PL diets (65 % WS) reduced the intake and impaired the digestibility of that diet before calving. After calving, the fibre pool increased considerably and consequently both intake and digestibility were increased.