Ammonia treatment of wheat straw. 2. Efficiency of microbial protein synthesis, rumen microbial protein pool size and turnover, and small intestinal protein digestion in sheep.

Ammonia-treated wheat straw (AWS) was compared with untreated wheat straw (UWS) and untreated wheat straw supplemented with urea (SWS) in an experiment with 6 wether sheep. Microbial protein synthesis increased after ammonia treatment due to the higher intake of rumen degradable organic matter (OM). The efficiency of microbial protein synthesis was low for all diets, averaging 22.1 g N/kg apparently rumen degradable OM and was not significantly affected by ammonia treatment. Estimates of microbial protein synthesis based on diaminopimelic acid or the amino acid profile methods did not differ significantly. The pool of microbial DM (average, 151 g) and N (12 g) in the rumen and the proportion of rumen microorganisms associated with the fluid phase (average, 36%) were not affected by diet, but the clearance rate (%/h) of microorganisms tended (P