Effects on chick performance and nutrient digestibility of an endo-xylanase added to a wheat- and rye-based diet in relation to fat source.

1. A study with growing chicks investigated the effects of an inclusion of an endo-xylanase preparation (LYXASAN) to a wheat- and rye-based diet on performance and nutrient digestibility in relation to the fat source. 2. The basal diet contained 500 g wheat and 100 g rye/kg of diet. The basal diet was supplemented with either 65 g soya oil/kg or 60 g blended animal fat and 5 g soya oil/kg. 3. Endo-xylanase added to the soya oil diet did not affect weight gain, but there was a numerical improvement in food conversion efficiency which was not statistically significant. When the endo-xylanase preparation was added to the blended animal fat diet, both weight gain and food utilisation were improved by 9.5% and 6.0%, respectively (P < 0.05). 4. Digestibilities of organic matter, crude fat, crude fibre and NFE were not significantly affected by adding endo-xylanase to the soya oil diet. However, when endo-xylanase was included in the blended animal fat diet, digestibility of organic matter, crude fat, crude fibre and NFE were improved (P < 0.05). The improvement in fat digestibility was the most pronounced, amounting to 9.4%. Nitrogen retention and metabolisable energy content were improved significantly by the addition of an endo-xylanase to the animal fat diet (P < 0.05), by 6.6% and 6.5% respectively. 5. From the results of this study, it can be concluded that the effects on chick performance and nutrient digestibility of a dietary endo-xylanase in a wheat- and rye-based diet are influenced to a considerable degree by the type of fat in the diet.