Effects of Xylanase on Performance, Blood Parameters, Intestinal Morphology, Microflora and Digestive Enzyme Activities of Broilers Fed Wheat-Based Diets (Report‪)‬

INTRODUCTION Although wheat is becoming an important source of energy in poultry diets, its high level of xylans, the principal water-soluble non-starch polysaccharides (NSP), limits its use. The presence of xylans increases the viscosity of the digesta, impeding the digestion and absorption of nutrients and causing poor performance (Almirall et al., 1995; Choct et al., 1995). There is considerable evidence that negative effects of NSP in poultry diets are related to the gut microflora of broilers, as supplementation of antibiotics to diets increases their nutritive value (Annison and Choct, 1991). Diet composition may produce microscopic alterations in the intestinal mucosa (Yamauchi, 2002) and it is possible that the change in morphology of the gastrointestinal tract (GIT) may be associated with dietary NSP levels. NSP also alters digestive functions and, in particular, digestive enzyme activities. It has been demonstrated in rats that there may be an attempt to compensate for the inefficiency of digestion and absorption with hyperplasia and hypertrophy of digestive organs and an increased secretion of digestive juice, although nutrient digestibility does not improve (Ikegami et al., 1990).