The effect of dietary phytase supplementation on the fattening performance and mineral balance of broilers

This study was carried out to determine the effect of the supplementation of microbial phytase in broiler feeds based on corn and soybean meal, to investigate its effect on broiler performance, dressing percentage and bone mineralization. In this experiment, 2000 1-day-old Ross 308 broiler chicks were used in five groups, each consisting of 400 chicks. Two of the groups were chosen as control groups (positive and negative), and the others were used as experimental groups. Each treatment group was divided into four replicates of 100 chicks. The first control group was fed a diet containing inorganic phosphorous but not phytase; the second control group was fed no inorganic phosphorous and phytase; and the third, fourth and fifth experimental groups were given Phytase Novo CT as an phytase enzyme throughout the experiment at the levels of 120 g/t, 200 g/t and 280 g/t (300 U/kg, 500 U/kg and 700 U/kg), respectively. The chicks were fed a broiler pre-starter diet for the first 10 days, broiler starter diet between days 10 and 20, broiler grower diet between days 20 and 30, and broiler finisher diet between days 30 and 42. The experimental period lasted 42 days. The body weight, live weight gain, feed consumption and feed conversion ratio of all the groups were determined every week during the experiment. Eight male and eight female chickens were slaughtered at the end of the experiment from each group. The weights and percentages of hot carcass, plasma inorganic phosphorus and tibia ash were determined. At the end of the experiment, the addition of microbial phytase to the diet significantly increased body weight (P < 0.001) and feed consumption (P < 0.01, P < 0.001) and improved the feed conversion ratio (P < 0.001). Hot carcass percentage was significantly increased (P < 0.001) by dietary phytase. In addition, there was an increase in tibia Ca, P and Mg (P < 0.001). All microbial phytases increased plasma inorganic phosphorus, though the differences were not statistically significant. In conclusion, the addition of 500 U/kg of microbial phytase at different levels led to the best fattening performance and carcass percentage in broilers.