EFFECT OF COLOSTOMY ON THE OCCURRENCE OF DIETARY [N-15]UREA IN INTESTINAL CONTENTS, BLOOD, URINE AND TISSUES IN CHICKENS FED A LOW-PROTEIN DIET PLUS UREA

1. The occurrence of N-15 was examined in excreta for 10 h, and in intestinal contents, blood and tissues at 10 h after [N-15]urea was fed to conventional and colostomised cockerels. 2. Total-N-15 excretion and N-15-balance in control chickens were 18.88 and 44.79 mg/kg body weight/10 h), respectively. The former was increased and the latter was decreased by colostomy by 10.75 mg (P < 0.01). 3. Amounts of [N-15]urea, [N-15]ammonia and [N-15]uric acid excreted by control birds were 13.78, 3.90 and 0.18 mg/kg body weight/10 h or 0.73, 0.21 and 0.01 of the total-N-15 excreted respectively. 4. The [N-15]urea, [N-15]uric acid and total-N-15 excreted were all increased after colostomy but [N-15]ammonia was decreased (uric acid P < 0.05, others P < 0.01). The increase in total-N-15 was mostly accounted for by [N-15]urea. 5. Colostomy resulted in significantly less total-N-15 in the contents of the whole intestine (P < 0.01), less total-N-15, [N-15]ammonia and [N-15]urea in the contents of the colo-rectum (P < 0.01) and less total-N-15 and [N-15]urea in the contents of the upper intestine (P < 0.05); it did not affect any in caecal contents. 6. [N-15]Urea in blood, liver and kidney (blood P < 0.01, others P < 0.05), and [N-15]glutamine amide (P < 0.05) and [N-15]uric acid (P < 0.01) in blood were significantly decreased after colostomy. 7. The results support the hypothesis that most of the dietary urea is utilised as the result of a back-flow of ureteral urea into the caeca where it is rapidly converted into ammonia which is then metabolised to other compounds.