INFLUENCE OF EXOGENOUS XYLANASE SUPPLEMENTATION ON APPARENT METABOLIZABLE 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 digestibi lities in wheat for broilers was investigated. The following three die tary treatments were tested: a basal diet containing 918 g kg(-1) whea t, basal diet plus enzyme 1 and basal diet plus enzyme 2. Each diet wa s 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 t he 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 exc reta amino acid digestibilities were calculated using acid-insoluble a sh as the indigestible marker. The AME values of wheat were markedly i mproved by exogenous enzymes. Addition of enzymes 1 and 2 improved the AME values by 12.6% and 1 8.6%, respectively. Supplementation of enzy mes resulted in significant (p<0.05) improvements hi ileal and excreta amino acid digestibilities in wheat. Mean excreta digestibility coeff icients 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 correspondi ng values at the ileal level were 0.78, 0.84 and 0.85, respectively. E xcreta digestibility of amino acids, with the exception of tyrosine, w ere found to be consistently lower than the ileal estimates. In the ca se of unsupplemented wheat, apparent digestibilities of individual ami no 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 w ere generally lowered by the addition of enzymes. (C) 1998 Elsevier Sc ience B.V.