On caecal synthesis and absorption of amino acids and their importance for nitrogen recycling in willow ptarmigan (Lagopus lagopus lagopus).

The willow ptarmigan has two large caeca housing dense populations of microorganisms. Urine, containing uric acid, is transported from the cloaca into the caeca when these are filled. Here the uric acid is rapidly broken down, suggesting that the caeca take part in a recycling of excretory nitrogen. In this work it is shown that ammonia produced by the uric acid decomposition is incorporated into new amino acids in a glutamic dehydrogenase catalyzed reaction. We have, however, not been able to detect any absorption of amino acids from the caeca, indicating that nitrogen recycling via the amino acid route does not occur.