Function and nutritional roles of the avian caeca: a review

The role of the avian caeca in the maintenance of gut health, fermentation of undigested nutrients, re-cycling of nitrogen from urine, and modulation of the gut microflora is not well understood. Thus, this review details the function of the avian caeca from anatomical, physiological, microbial and nutritional points of view in the context of poultry production. Due to anatomical and physiological adaptations, only small and/or soluble particles will be refluxed into the caeca together with urine and digestive fluids. Here, salts and water will be reabsorbed, and uric acid and carbohydrates will be fermented by the abundant microflora to ammonia and volatile fatty acids. Thus, the caeca may play a role for the nutritional status of the bird, although the quantitative significance for high-yielding domesticated poultry remains to be elucidated.