Ninety-six crossbred pigs weighing 7.8 kg were used in a 5-week trial to determine the effectiveness of microbial phytase in improving the bioavailabilities of phosphorus and other nutrients in a corn-soybean meal diet. A 2x5 factorial arrangement of treatments was used with two available phosphorus levels and five phytase levels. The addition of graded levels of phytase resulted in linear increases in average weight gain, average daily feed intake, weight gain to feed intake. The addition of phytase also linearly increased the apparent digestibilities of phosphorus and calcium, whereas fecal phosphorus excretion was linearly decreased. Linear increases in shear force, shear energy and ash content of selected bones were related to phytase supplementation. The maximum responses occurred at a phytase level of 1050 U/kg diet for the 0.7 g available phosphorus/kg diets and 700 U for the 1.6 g available phosphorus/kg diets. The researchers calculated that the replacement one gram of inorganic phosphorus, as deflourinated phosphate, would require about 246 U of microbial phytase per kg of diet.

Kornegay, E.T. and H. Quan. 1996. Replacement of inorganic phosphorus by microbial phytase for young pigs on a maize-soyabean-meal diet. British J. Nutrition. 76(4):563-578.