MEASUREMENT OF BIOAVAILABLE ENERGY IN POULTRY FEEDINGSTUFFS: A REVIEW

The importance of knowing the bioavailable energy (BE) content of poultry feedingstuffs is discussed in terms of economics, feed intake and the environment. The partition of ingested dietary energy is described and the effects of nutrient intake and of the microflora of the alimentary canal are outlined. Indirect biological, physical and chemical assays for BE are described and appraised. Procedures common to several direct bioassays for BE are discussed and points to consider in choosing between total excreta collection and the use of an indicator are presented. Assays for digestible energy, apparent metabolizable energy, true metabolizable energy and net energy are described. Variables affecting estimates of BE such as bird type, assay environment, assay diet and intake, assay design, the nitrogen correction, and metabolic plus endogenous losses are considered and a bioassay is recommended. The review concludes with brief speculation about future developments in the field of feedingstuff evaluation. Key words: Review, Energy, Assays, Methodology, Bioavailable