Effect of colostomy on the occurrence of dietary [15N]urea in intestinal contents, blood, urine and tissues in chickens fed a low protein diet plus urea

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Abstract
1. The occurrence of 15N was examined in excreta for 10 h, and in intestinal contents, blood and tissues at 10 h after [15N]urea was fed to conventional and colostomised cockerels. 2. Total‐15N excretion and 15N‐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 (P15N]urea, [15N]ammonia and [15N]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‐15N excreted respectively. 4. The [15N]urea, [15N]uric acid and total‐15N excreted were all increased after colostomy but [15N]ammonia was decreased (uric acid PP15N was mostly accounted for by [15N]urea. 5. Colostomy resulted in significantly less total‐15N in the contents of the whole intestine (P15N, [15N]ammonia and [15N]urea in the contents of the co!o‐rectum (P15N and [15N]urea in the contents of the upper intestine (P< 0.05); it did not affect any in caecal contents. 6. [15N]Urea in blood, liver and kidney (blood PP< 0.05), and [15N]glutamine amide (P< 0.05) and [15N]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.