Effect of diet on protein degrading activity in the sheep rumen.

Abstract

AbstractComparative studies on the effect of diet on ruminal protein degrading activity were made with sheep fed either maize or timothy and with sheep fed either barley or lucerne. In both studies the levels of proteolytic activity and deaminase activity in the rumen, measured as non‐protein nitrogen and ammonia production, respectively, during in‐vitro incubation of rumen liquor and casein, were higher when cereal was given than when forage was given. The rate of casein degradation after intra‐ruminal infusion was also higher with the cereal diets, whereas outflow rate from the rumen was lower. However, with all diets the fractional hydrolysis rate of casein was considerably greater than its fractional outflow rate and the calculated proportion of protein escaping ruminal breakdown was low. The effect of diet on the degradation of the protein of natural feedstuffs was examined by measuring N disappearance when samples of the four feeds and of three protein supplements (soya bean meal, groundnut meal and fish‐meal) were incubated in dacron bags in the rumen. In contrast to the findings with casein, the rate of N disappearance for all feedstuffs, except maize which was similar on the two types of diet, was lower when sheep were given cereal than when given forage.