A five week feeding study was carried out to assess the effects of phytase enzyme with different level of calcium and available phosphorus on Ross 308 broilers on performance, carcass traits and deposition of calcium and phosphorus on serum and tibia of broiler chickens. One hundred and sixty-eight one day-old Ross 308 broiler chicks were used. The birds were weighed and assigned to equal six treatment groups with fixed calcium to phosphorus ratio 2:1. Each two treatments have the same value of available phosphorus according feeding stage but one of them with supplementation of Hiphos GT (100gm/ton phytase enzyme unit FTU/Kg) and the other one without supplementation in a completely randomized design. Each treatment had four replicates and each replicate contains seven chicks. The results showed that phytase enzyme supplementation with available phosphorus 0.5% and 0.45% significantly elevated (P < 0.05) body weight, body weight gain and feed intake, and reduced (P < 0.05) feed conversion ratio in starter period. All parameters in grower, finisher period and overall showed non-significant for all groups. Moreover, the highest significant value from all other groups in liver enzymes Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum, founded in broilers fed the diet with phytase enzyme and available phosphorus 0.40% and without phytase enzyme in creatinine. Calcium value with available phosphorus 0.35% with phytase enzyme showed high significance. In Phosphorus we found that usage of phytase enzyme with available phosphorus 0.30% and 0.35% as same as 0.35% without phytase. In weight, eviscerated and dressing usage of phytase enzyme with available phosphorus 0.4% revealed the highest significant difference from all groups. Thigh, breast and drumstick value showed non-significant difference from all other groups.

A five week feeding study was carried out to evaluate the effects of different levels of calcium, available phosphorus (AP) on broiler performance, carcass traits and deposition of calcium and phosphorus in serum and tibia of broiler chickens. Two hundred and fifty two one day-old Ross 308 broiler chicks were used. The birds were weighed and assigned to equal nine treatment groups: three calcium to phosphorus ratios were used, 2:1, 1.75:1, and 1.5:1, there were three different values of available phosphorus for each calcium into phosphorus ratio according to the feeding stage. Each treatment had four replicates and each replicate contained seven chicks. The results showed that during starter stage, performance at available phosphorus 0.5% and 0.45% were significantly higher than that of 0.4% regardless of calcium levels for body weight, body weight gain and high feed intake, but during the finisher period, there was no significant difference between treatments. Treatment with Ca level 1.5 and AP 0.4% is the same result of treatment with Ca level 2 and AP 0.5%in all stages. Treatment with Ca level 1.75 and AP 0.35% showed the highest serum ALT, Ca and P measurements and non-significant changes  in treatments with AP 0.4. AST and creatinine in treatments with AP 0.3% showed significant decreases compared to treatments with AP 0.4%. Increasing of Ca level and P availability resulted in decreased Ca levels in ash in all stages. Increasing P availability resulted in decreased P levels in all stages. Phosphorus availability 0.4% showed high significant differences from AP 0.3% in weight, eviscerated, dressing and breast. Drumstick and thigh in all treatments were the same except the high Ca level 1.5 with AP 0.35% and Ca level 2 with AP 0.3%, which showed the lowest significant difference from other treatments. It could be concluded that calcium (Ca) and phosphorus (P) utilization at low rate with low available phosphorus could be effective.