Carbohydrate fermentation in the avian ceca: a review

Poultry diets are primarily based on plant proteins, with carbohydrates serving as the principal source of energy. There is usually no problem digesting most of the sugars as well as starch in the poultry gastrointestinal tract (GIT). However, some carbohydrate fractions, such as dietary fibre (DF), are not hydrolyzed by avian gastrointestinal enzymes but are fermented by the resident anaerobic microflora. Unfortunately, problems can occur with the feeding of dietary fibre due to the physicochemical properties (i.e. viscosity) of the non-starch polysaccharides (NSPs). It has been shown that components of NSPs, including pentosans (arabinoxylans), pectins, and β-glucans have negative effects in the poultry gastrointestinal tract. The anti-nutritive nature of NSPs in poultry diets has been well documented, but data regarding the fermentation of these and other carbohydrates by cecal microorganisms are limited. Concentrations of short-chain fatty acids (SCFA) are highest in the cecum compared with other areas of the avian gastrointestinal tract. It has been suggested that the short-chain fatty acids may inhibit the growth of pathogenic bacteria whilst in addition providing some energy-yielding substrates to the host animal after absorption. The objective of the current paper is to provide an overview of carbohydrate fermentation in the avian ceca as well as to focus on some potential advantages to the bird of this fermentation.