Influence of dietary enzyme complex on the performance of broilers fed on diets with and without antibiotic...

1. The aim of the experiment was to test the possible interactions of an enzyme complex and a food antibiotic on the growth and metabolism, carcase yield, whole body composition and nutrient deposition in broilers. The basal diet contained 400 g/kg barley. The four treatments were as follows: O--without supplements (control), E--enzyme complex Roxazyme G, 200 mg/kg, A--antibiotic avoparcin, 10 mg/kg, EA--Roxazyme G, 200 mg/kg plus avoparcin, 10 mg/kg. 2. Roxazyme G positively influenced weight gain, food conversion efficiency, energy metabolisability, fat and nitrogen utilisation and the dry matter content of droppings. Fat and energy deposition in the whole body were also increased, whereas protein deposition and carcase yield were not influenced. 3. Avoparcin increased energy metabolisability and fat utilisation, but had no influence on nitrogen utilisation. No significant improvements from avoparcin were seen in growth or in nutrient deposition in the body. The fibre degradability (NDF and ADF fraction) was significantly depressed by antibiotic supplementation. 4. The inclusion of both supplements to the diet did not have a fully additive effect on growth, energy metabolisability, or fat and nitrogen utilisation. The interaction between enzyme and antibiotic for food conversion efficiency during the first experimental period (7 to 21 d) was nearly significant (P = 0.053). Except for fibre degradability (P < or = 0.01), no other significant interactions between enzyme and antibiotic were found.