NR 33. Effect of phenolic compounds release from straw by ammonia treatment on fibrolytic microbial activity

Abstract

The effect of release of phenolic compounds promoted by ammonia treatment of straw on rumen microbial action over structural polysaccharides was studied. Samples of barley straw (PC) and ammoniated straw (PT) were incubated in the rumen of sheep fed on either untreated straw plus urea (PU) or PT. Phenolics were solubilized in a higher extent from PT than from PC. Microbial adhesion was higher in PT as substrate (P<.001), and also with PT diet (P<.05), showing that phenolics had little influence on attachment mechanisms. Total polysaccharidase activity was higher in PT as substrate, but there was a fermentation lag between 4 and 8 h, until phenolics become metabolised. Total and specific enzymatic activity were higher in PU diet, showing that phenolic release inhibits enzyme synthesis and hydrolytic activity.