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.