Influence of exogenous xylanase supplementation on apparent metabolisable energy and amino acid digestibility in wheat for broiler chickens

The influence of two commercial xylanase preparations on the apparent metabolisable energy (AME) and, ileal and excreta amino acid digestibilities in wheat for broilers was investigated. The following three dietary treatments were tested: a basal diet containing 918 g kg^?1 wheat, basal diet plus enzyme 1 and basal diet plus enzyme 2. Each diet was offered ad libitum to four pens (four birds/pen) from day 35 to day 42 post-hatching. Total collection of excreta was carried out during the last 4 days. All birds were euthanatised on day 42 and the contents of the lower half of the ileum were collected. Apparent ileal and excreta amino acid digestibilities were calculated using acid-insoluble ash as the indigestible marker. The AME values of wheat were markedly improved by exogenous enzymes. Addition of enzymes 1 and 2 improved the AME values by 12.6% and 18.6%, respectively. Supplementation of enzymes resulted in significant (p<0.05) improvements in ileal and excreta amino acid digestibilities in wheat. Mean excreta digestibility coefficients of the 15 amino acids in wheat, wheat plus enzyme 1 and wheat plus enzyme 2 were 0.70, 0.78 and 0.79, respectively. The corresponding values at the ileal level were 0.78, 0.84 and 0.85, respectively. Excreta digestibility of amino acids, with the exception of tyrosine, were found to be consistently lower than the ileal estimates. In the case of unsupplemented wheat, apparent digestibilities of individual amino acids measured in excreta were 5–22% units lower (p<0.10–0.01) than those measured at the terminal ileum. The ileal-excreta differences were generally lowered by the addition of enzymes.