Mestrado em Engenharia Zootécnica - Produção Animal - Instituto Superior de Agronomia / Faculdade de Medicina VeterináriaThe nutritional value of wheat varieties depend on the content of non-starch polysac-charides which cannot be degraded by monogastric animals. Supplementation with exogen-ous enzymes can improve digestion and nutrient availability, but represents an expensive cost when it is used throughout the production cycle. This study analyzed the restriction of enzyme supplementation to specific periods. One hundred and twenty broilers were fed a wheat based diet supplemented (B4 – from 1-36 days; B3 – from 9-36 days; B2 – from 18-36 days; B1 – from 27-36 days) or not (B0), in different periods, with a commercial xylanase. Feed consumption and individual body weight were recorded weekly. At day 36, 8 birds per treatment were killed, digesta samples were collected from the gastrointestinal compart-ments for viscosity and enzyme activity. Weights and lengths of the digestive organs were measured. There was an improvement of body weight and feed conversion ratio in B4, B3 and B2 birds compared to B0. The viscosity of the ileum digesta in treatment B4 was lower than B0. There were no significant differences in the sizes of the organs of the digestive tract. Overall, we conclude that it is possible to restrict the supplementation of xylanase to the final period of the production cycle
