Non-starch polysaccharides and enzyme application influence the net energy value of broiler diets

The apparent metabolisable energy (AME) assay is a default system of energy estimation in the poultry industry, but the system is not capable of accounting for losses of chemical energy in the solid, liquid and gaseous excreta or as heat (Pirgozliev and Rose, 1999). Measuring energy lost to account for heat increment (HI) and excreta volatile fatty acids (VFA), and thus calculating the net energy (NE) of the diet, should better explain the negative influence of non-starch polysaccharides (NSP) and benefits of their breakdown by xylanases. Four groups of day-old mixed broiler birds (Cobb strain), each consisting of 2 randomly selected birds of similar weights, were selected from 2 different batches. On d 17 birds were transferred to 4 closed circuit respiration chambers (2 per cage) in a climate-controlled room (25 ± 2°C) under continuous fluorescent lighting. On d 4 and 5, the birds were deprived of feed to establish their basal metabolism and fasting heat (FH). During d 6-9, they were fed a wheat-based diet containing 4% soluble NSP, and that diet with a xylanase product (250 mg Ronozyme WX), followed by collection of excreta collection for determination of AME, as well as measures for respiratory quotient (RQ), heat production (HP) and HI during d 10-14. On d 14 after the last collection, all the birds were sacrificed, and intestinal contents were collected for digesta viscosity (data not shown) and VFA analysis.