INHIBITORY EFFECT OF PENICILLIN ON CECAL UREASE ACTIVITY IN CHICKENS FED ON A LOW-PROTEIN DIET PLUS UREA

1. The effects of dietary penicillin on the urease activities of small intestine, large intestine, caecum and their contents, liver and kidn ey in chickens fed a diet containing 5 g/kg protein plus urea were exa mined. 2. About 0.88 of the total urease activity determined was obser ved in intestinal contents, of which 0.95 of the activity was accounte d for by caecal contents, 0.05 by colo-rectal contents and none by sma ll intestinal contents. Intestinal tissues (caecum included), liver an d kidney accounted for 0.03, 0.06 and 0.02, respectively, of the total urease activity. 3. Dietary penicillin decreased urease activity to 0 .17 in caecal contents and to 0.05 in colo-rectal contents of the corr esponding control values (P < 0.01). The urease activity of caecal tis sue was lowered by penicillin to half that of control activity (P < 0. 05) but none of the activities of other tissues were affected. 4. It i s concluded that, even when the urease activity is stimulated by dieta ry urea, 20 mg/kg dietary penicillin can strikingly lower it in the ca ecum, where most of the urease activity in the chicken body is to be f ound.