Ammonia and amino acids modulates enzymes associated with ammonia assimilation pathway by ruminal microbiota in vitro

The objective of this study was to evaluate the effects of ammonia and amino acids (AA) supplementation on activities of ruminal enzymes involved in ammonia assimilation. In addition, the temporal changes of ruminal bacterial populations and enzyme activities during in vitro incubation were investigated. Rumen fluid from four ruminally fistulated goats was used in a 3×3 factorial arrangement of treatments with ammonia equivalent to 1, 4, and 15 mM ammonium chloride (NH4Cl), and with an added AA mixture (containing 992 g casein acid hydrolysate plus 1.4 g l -cysteine plus 8.68 g l -tryptophan) at 0, 1, and 15.5 g/L in the in vitro culture solution. Both ammonia and AA supplementation increased (P