The caeca of the domestic fowl and digestion of the crude fibre complex

Abstract

Synopsis Direct methods of investigating caecal function in poultry are presented, involving the use of a caecal fistula. Food materials contained in a porous bag inserted into the caecum via the fistula underwent digestion, as evidenced by weight loss; the extent to which they were digested depended on the nature of the material and the length of time it remained in the caecum. Chemical analysis of bran and hay gave no indication of what classes of compounds were being digested. Caecal contents were removed from the fistula and incubated with food materials, forming an artificial caecum in vitro. Food materials were also introduced into the intact caecum isolated from the bird. Incubation of a carbohydrate substrate with caecal material in these ways led to its breakdown into simpler soluble carbohydrates and then into acidic products, including probably pyruvic and lactic acids. It is possible that the first stage of the breakdown occurs outside the bacteria which are responsible for it, and the later stages take place intracellularly, after the products of the first stage have been absorbed.