Effect of pelleting temperature on the recovery and efficacy of a xylanaseenzyme in wheat-based diets

Two trials were performed to test the stability and efficacy of a commercia l enzyme preparation containing xylanase and protease activities to pelleti ng. In Trial 1, 576 male Cobb chicks were fed wheat-based diets to 21 d wit h or without enzyme and pelleted after conditioning for 55 or 140 s at 70, 75, 80, 85, 90, or 95 C. In Trial 2, 2,880 male Cobb chicks were fed wheat- based diets to 42 d with no enzyme, or with enzyme addition before or after pelleting with conditioning for 30 s at 70, 80, 90, or 95 C. Enzyme additi on had a positive effect on BW gain and the feed to gain ratio (FG) in Tria l 1 and on FG to 42 d in Trial 2. All treatment effects were significant fo r intestinal viscosity in both trials. Two- (BW) and three-way (BW, FG) int eractions between enzyme, temperature, and time were seen in Trial 1. With enzyme supplementation, second degree polynomial equations of performance o n conditioning temperature had high R-2 values for BW and FG, with temperat ures between 80 and 85 C being most favorable. Enzyme activity in unsupplem ented diets measured in vitro was largely eliminated at temperatures above 80 C, whereas the decline in activity in supplemented diets was linear. In spite of the decline in enzyme activity measured in vitro, intestinal visco sity of chicks fed enzyme-supplemented diets remained low with high process ing temperatures, whereas that of chicks fed unsupplemented diets increased dramatically.