FACTORS INFLUENCING RUMINAL BACTERIAL-ACTIVITY .1. EFFECT OF ENDPRODUCT CONCENTRATION ON PROTEOLYTIC ACTIVITY

The influence of the concentration of ammonia, volatile fatty acids (V FA; a 70:20:10 mixture of acetate, propionate and butyrate) and free a mino acids (a mixture containing equal amounts of alanine, aspartic ac id, isoleucine, lysine, methionine and tyrosine) on the casein-degradi ng capacity of washed rumen bacteria was studied in an in vitro experi ment. The end-products of the ruminal proteolysis were applied at the following range of concentrations: 0-47.0 mM ammonia, 0-500.0 mM VFAs and 0-60 mM free amino acids. Ammonia reduced the amount of degraded p rotein only when the ammonia occured in a relatively high concentratio n (above 19 mM; y = 28.0 - 0.01x; correlations coefficient r = -0.86). At concentrations higher than 133 mM, VFAs increased the activity of proteases (y = 0.056x + 16.57; correlations coefficient r = 0.999) at a considerable rate (125-182% of control value was established). At th e same time, the amino acid mixtures reduced protease activity in a co ncentration-dependent manner (y = -0.63x + 38.93; correlations coeffic ient r = 0.99).