The Use of Phytase and Low Phosphorus Levels in Broiler Diets with Different Metabolizable Energy Levels

The objective of this study was to determine the effects of dietary available phosphorus (AP), phytase supplementation and metabolizable energy (ME) levels on performance and bone and blood characteristics of broiler chickens. An experiment in completely randomized design with 2 × 2 × 2 factorial arrangement were conducted, in which two phytase levels (0 and 500 mg/kg), two AP levels (NRC and 15% lower) and two ME levels were used. The ME ratios to CP and other nutrients (except phosphorus) were equal in all treatments. Average weight gain, feed intake, and feed conversion ratio (FCR) of starter, grower and total rearing period were analyzed. Bone calcium and phosphorus, blood calcium, phosphorus and alkaline phosphatase at 6 weeks of age were analyzed. Based on growth parameters, low AP level had equal or better effects than high AP level. Chickens fed diets with high ME levels had better performance. Phytase had no significant effects on weight gain, whereas it enhanced FCR. Adding phytase in low energy diets improved body weight gain and FCR. Phytase in diets with low AP levels significantly enhanced FCR. Using low AP in high and low energy diets, caused better FCR in starter and whole rearing phase consequently. Available phosphorus and phytase supplementations had no significant effects on tibia ash; however, it was inversely affected by low AP level. The results of this experiment indicated that it is possible to decrease dietary AP level up to 15 percent less than NRC recommends. Adding AP and phytase did not significantly affect growth parameters of the chicks fed low energy diets.