Reducing nitrogen and phosphorus excreted from broilers through feed manipulation

Three experiments were carried out to study the effects of reducing dietary nitrogen and phosphorus and/or adding enzymes to different broiler diets on performance, carcass characteristics, bone measurements and excretion of N, Ca and P. The first experiment examined the effect of reducing dietary crude protein level and adding avizyme@ ( xylanase, protease and amylase) 1g/ Kg diet. Three feed regimens were formulated, a control high crude protein (HCP), medium CP (MCP) and low CP (LCP) and applied for starting, growing and finishing periods. The second experiment was designed to study the effect of reducing dietary P and adding phytase enzyme (500 U/Kg diet) to low P diets during starting period (from 1 to 20) and growing period (from 21 to 35 days of age). The third experiment was designed to study the effect of reducing dietary dicalcium phosphate (DCP) and adding phytase enzyme (500 U/Kg diet) to low and no DCP diets during the finisher period from 23 to 40 days of age. The results indicated that addition of enzyme to low CP diets enhanced performance of broiler chicks only during starter period. BWG, FI and FCR did not significantly differ when birds were fed HCP or MCP diets. Reducing CP or added avizyme did not significantly affect carcass characteristics and significantly (P0.001) decreased N excretion. , Reducing AP levels with phytase supplementation improved performance and decreased Ca and P excretion. Reducing AP levels with or without phytase supplementation did not (P0.05) affect. carcass characteristics and significantly decreased (P0.01) tibia bone measurements but this effect disappeared when phytase was added to the diet. Reducing dietary DCP level from 1.48 to 0.74 % (50% of the requirements) or reducing DCP down to 0.37% (25% of the requirements) with phytase supplementation of broiler diets did not negatively affect growth performance. Reducing DCP and /or added phytase slightly decreased abdominal fat%. Decreasing dietary DCP showed significant (P0.001) decrease in the excreted Ca and P. Addition of phytase to diets of 0.37 or 0.0% DCP decreased (P0.001) the excreted Ca and P %. From the obtained results it could be concluded that reducing dietary CP or P level and using enzymes could be used to limit quantity of N, Ca and P excreted from broilers without adverse affect on performance. This reduces such impact in environmental pollution. Further studies are recommended on removal of DCP from broiler finisher diets.