The use of microbial phytase in grower and finisher pig diets

The objective of this study was to evaluate the use of microbial phytase as a means of reducing inorganic phosphorus (P) supplementation and faecal P excretion in pigs. A 3 X 2 X 2 factorial arrangement was used to evaluate t he response of grower-finisher pigs to three supplemental phytase (Innozyme ) levels (0, 300 and 600 units/kg), two levels of total P (4.5 and 5.5 g/kg ) and two levels of Ca (8.25 and 6.75 g/kg). The diets were formulated to h ave identical levels of digestible energy and lysine and contained wheat (3 00 g/kg), barley (137 g/kg), soyabean meal (154 g/kg), rapeseed meal (110 g /kg), peas (200 g/kg), tallow (40 g/kg), molasses (30 g/kg), minerals and v itamins. Seventy-two pigs, averaging 31 kg in live weight, 36 males and 36 females were allowed to consume their diet ad libitum. Twelve entire male p igs, averaging 42 kg in live weight, were randomly allocated to the diets i n a digestibility study for four collection periods and fed according to 0. 90 of estimated ad libitum intake. There were no phytase, Ca or P effects f or growth performance (P > 0.05). Kill-out proportion (P < 0.01) and carcas s weight (P < 0.01) increased with increasing levels of phytase. Bone stren gth (P < 0.05) and the digestibility of P, ash and protein increased (P < 0 .01) with increasing levels of phytase. Phytase supplementation decreased f aecal-P output (P < 0.001). Reducing the total P in the diet decreased faec al-P output (P < 0.001). There was a significant interaction between phytas e X Ca for digestibilities of dry matter (P < 0.001) and energy (P < 0.05). Pigs fed the low-Ca diet containing 600 units of phytase / kg had higher d ry matter and energy digestibilities than pigs fed the corresponding high-C a diet, whereas pigs fed the low-Ca diet containing either 0 or 300 units o f phytase had similar digestibilities.