AMMONIA TREATMENT OF WHEAT-STRAW .1. VOLUNTARY INTAKE, CHEWING BEHAVIOR, RUMEN POOL SIZE AND TURNOVER AND PARTITION OF DIGESTION ALONG THE GASTROINTESTINAL-TRACT OF SHEEP

The impact of ammonia treatment of wheat straw on intake and digestion and passage kinetics was studied with 6 wether sheep. Ammoniated wheat straw (AWS) was compared with untreated wheat straw (UWS) and untreated wheat straw supplemented with urea (SWS). Ammonia treatment increased intake and whole tract digestion without affecting rumen pool size and rate of passage significantly. The increased cell wall intake due to ammonia treatment could for 91 % be attributed to a higher rumen degradation of cell walls. No significant effects of ammonia treatment on concentration, molar composition or rate of absorption of volatile fatty acids were observed. The rate of passage in the hindgut and the contribution of the hindgut to whole tract digestion were not significantly affected by ammonia treatment. Rumination and eating time and daily number of rumen contractions did not differ between rations, but AWS showed a lower rumination time per kg NDF ingested than the control rations. Whole tract digestion and rumen degradation of hemicellulose increased more due to ammonia treatment than those of cellulose. The effects of ammonia treatment could not be attributed to N supplementation, since no effect of urea supplementation on any parameter, except rumen ammonia-N concentration was observed.