An experiment was conducted to evaluate the effects of phytase supplementation on the growth performance, nutrients utilization and bone mineralization in broiler chickens. Day-old broiler chicks (n=480) were equally devided into eight treatment groups and fed maize or wheat based isocaloric, isonitrogenous and isocalcium diets having two non phytate phosphorus (NPP) concentrations (0.50% and 0.30%) and two phytase levels (0 and 500 phytase units/kg diet) in a 42 days growth trial. Maize based dietary treatments were MC (NPP 0.50%, MN (NPP 0.30%), MNP (MN+500 units of phytase) and MCP (MC+500 units of phytase), whereas wheat based experimental diets were WC (NPP 0.50%), WN (NPP 0.30%), WNP (WN+500 units of phytase) and WCP (WC+500 units of phytase). The NPP levels were maintained by dicalcium phosphate. Reduction in dietary NPP depressed live weight gain and feed intake and increased feed conversion ratio (FCR). Phytase supplementation to low NPP (0.30%) diets significantly (p<0.05) improved the growth performances of broilers. The supplementation to low NPP diets allowed complete, safe and economic replacement of dietary inorganic P (dicalcium phosphate) to reduce feed cost per kg live weight gain of broilers. Reduction in dietary NPP did not affect retention of nutrients except phosphorus (P) but had a significant (p<0.05) depression in tibia ash and minerals (Ca, P) concentration in serum and tibia ash. Phytase supplementation at low NPP level was effective (p<0.05) in improving the retention of dry matter, Ca and P and Ca and P concentration in serum and tibia ash. However, the supplementation was not effective at high level of NPP (0.50%). There were no significant (p>0.05) differences in carcass quality among dietary treatments. The response of phytase was greater in low NPP and maize based diets as compared with high NPP and wheat based diets, respectively. The results show that phytase supplementation to low NPP (0.30%) diets improved the growth performance, relative retention of nutrients (N, Ca and P) and minerals (Ca, P) status of blood and bone in broiler chickens, with a better efficacy in maize based diets.

A 42-day trial was conducted to assess the effects of a dietary protease on growth performance and ileum population of selected bacteria in broiler chickens fed standard diets and diets deficient in crude protein and digestible amino acids (CP/AA, ~5%) or apparent metabolizable energy (AME, 50 kcal/kg) or both. Reducing CP/AA and AME negatively affected average daily weight gain (ADG, P < 0.05) and feed conversion ratio (FCR, P < 0.05). Dietary protease improved BW at 42-d (P = 0.021, linear effect) of birds fed both standard and nutrient deficient diets but improved FCR (P = 0.0002) was only observed when supplemented to the standard diet. Serum protein concentration was not affected by the level of CP/AA and AME but decreased linearly with the level of protease (P = 0.02). Numbers of Escherichia coli¸ Salmonella spp. and Clostridium perfringens increased (P = 0.0001) with the decrease of dietary CP/AA and AME. In contrast, the numbers of studied bacteria linearly decreased (P = 0.0001) with dietary protease level. Dietary protease was found to decrease the numbers of Clostridium perfringens (P = 0.0001) when supplemented to either low CP/AA or low AME diets. It can be concluded that protease supplementation sustained the harvesting biomass in the experimental birds fed lower nutrient density diets and decreased the numbers of resident bacteria in the hind gut, some of which might be potential pathogens. Hence, the study documented not only the nutrient sparing effects but also the extra-proteinaceous effect in terms of gut health of dietary protease in broiler chickens.