Ammonia absorption from different parts of chicken intestine and its quantitative evaluation in situ

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

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 (P < 0.01). 3. Amounts of [15N]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 P < 0.05, others P < 0.01). The increase in total-15N was mostly accounted for by [15N]urea. 5. Colostomy resulted in significantly less total-15N in the contents of the whole intestine (P < 0.01), less total-15N, [15N]ammonia and [15N]urea in the contents of the colo-rectum (P < 0.01) and less total-15N 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 P < 0.01, others P < 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.

Ammonia production from uric acid and its absorption from the caecum of the cockerel

1. Experiments were done in vitro and in situ in the caeca to measure ammonia production from uric acid and its absorption. 2. When uric acid was introduced into a caecal sac containing mixed caecal micro-organisms 0.77 disappeared in 1 h, with the concomitant appearance of ammonia. 3. Amounts of ammonia produced from added [15N] uric acid in the caeca in situ after 30 min and in caecal medium in vitro after 10 h, were 0.28 and 0.25 respectively of the added 15N. 4. About 0.92 of the ammonia introduced into a caecal sac disappeared from the lumen fluid in 30 min. 5. It is concluded that ammonia is produced from uric acid by caecal micro-organisms and rapidly absorbed.