Effectiveness of exogenous microbial phytase in improving the bioavailabilities of phosphorus and other nutrients in maize-soya-bean meal diets for broilers

A 3-week feeding trial using 300 1-day-old male broiler chicks was conducted to evaluate the effects of adding three levels of a microbial phytase (Finnfeed phytase; 250, 500 and 1000 U per kg diet) to a maize-soya-bean-meal diet containing 3.0 g/kg non-phytate phosphorus and 8.0 g/kg calcium. A diet containing 4.0 g/kg non-phytate phosphorus and 9.0 g/kg calcium served as the positive control. The responses were evaluated in terms of broiler performance, toe ash contents, ileal phytate degradation, ileal digestibility of nitrogen, amino acids, phosphorus, starch and fat, apparent metabolizable energy, apparent ileal digestible energy, and apparent retention of phosphorus and nitrogen. The addition of 500 U phytase per kg diet to the phosphorus-deficient maize-Soya-bean-meal diet improved the performance and toe ash contents of broilers to equal those given the positive control diet. Ileal phytate degradation data provided direct evidence to the efficacy of phytase in hydrolysing the phytic acid. Addition of 500 U phytase per kg to the maize-soya-bean-meal diet which contained 3.0 g phytate-phosphorus per kg resulted in more than doubling of phytate degradation from 0.218 to 0.481. Supplemental phytase improved ileal digestibility of nitrogen, amino acids, starch and lipids, with these improvements being eventually reflected in enhancements in ileal digestible energy and apparent metabolizable energy.