Enzyme supplementation of rice bran based broiler diets
Rice bran arises as a by-product from rice milling industry. The anti-nutritional substances such as phytate, non-starch polysaccharides, protease inhibitor and lectin limit the nutritional value of this by-product. This research was directed toward the nutritional improvement of defatted rice bran (DRB) using feed enzymes to degrade these anti-nutritional factors. Three growth experiments and two tube feeding experiments were carried out to investigate the effect of phytase, carbohydrase and protease enzymes (supplied by Finnfeeds International) on broiler performance, mineral retention, nutrient digestibility, digesta viscosity and bone characteristics of chicken fed defatted rice bran based broiler diets. Enzyme supplementation of diets was conducted to assess the effects of individual and a cocktail of enzymes and/or lactobacillus culture. The data showed that inclusion of DRB at more than 150 g/kg without additional inorganic phosphate reduced feed intake, growth, bone mineralisation and produced the symptoms of rickets in broiler chickens. Experimental phytase successfully released phosphorus from DRB which counteracted the symptoms of a phosphorus deficient rickets-producing diet and improved feed intake, growth and bone mineralisation. Data presented in this study indicate that inclusion of DRB in broiler diets did not produce viscous digesta in the gut and carbohydrase supplementation did not improve bird performance, nutrient digestibility and mineral retention. The digesta viscosity was not decreased by carbohydrase; therefore, the non-starch polysaccharide (NSP) content of DRB did not play an important role in production of viscous digesta. Supplementation of DRB based broiler diets with protease improved dry matter (DM) and protein digestibility and P retention; therefore, the improvement in feed conversion ratio (FCR) was a result of better utilisation of nutrients. The data showed that there is a potential to decrease the phytate and lectin content of DRB broiler based diets by supplementing diets with phytase and protease.