Effect of wheat content, fat source and enzyme supplementation on diet metabolisability and broiler performance

1. A 3x3x2 factorial experiment studied the interactions of fat source (tal low, soya, tallow: soya [2:1] blend), wheat level (700, 350, 0 g/kg) and en zyme inclusion (Avizyme 1300, absent, present) in diets for broilers fed ad libitum in individual cages from 7 to 35d. Bird performance, fat digestibi lity, viscosity of ileal contents and diet metabolisability (AME) were meas ured. 2. There were no significant effects of fat source on bird performance. How ever, there was a significant effect on fat digestibility, which was highes t for soya and lowest for tallow. Diet AME content was also significantly a ffected by fat source and reflected differences in fat digestibility. 3. Dry matter (DM) intake, liveweight gain (LWG) and gain: food were all re duced at 700 g wheat/kg. Viscosity of ileal contents increased with increas ing wheat inclusion. 4. There were no significant effects of enzyme on DM intake or LWG but gain : food was improved by 2%. Diet AME content was increased with enzyme addit ion, the effect being greatest (9%) with tallow at 700 g wheat/kg. 5. Viscosity of ileal contents was reduced and fat digestibility increased with enzyme addition and there were significant wheat enzyme interactions a ttributable to no differences with zero wheat but marked responses to enzym e at 700 g wheat/kg. 6. The results confirm important interactions between wheat content and fat composition in relation to fat digestibility, AME content and food efficie ncy.