Evaluation of different microbial phytases on phosphorus digestibility in pigs fed a wheat and barley based diet

Phytase increases the availability of phytate phosphorus (P) in plant feedstuffs resulting in a reduced need for inorganic P addition and therefore minimized P excretion. Thus, the majority of pig feed is supplemented with microbial phytases. The present study aimed to examine three commercial phytases: one fungal 3-phytase from Aspergillus ficuum and two formulations of a bacterial 6-phytase from E. coli. The basal diet was composed of wheat, barley, soybean and rapeseed meal supplemented with vitamins and minerals without any added inorganic phosphate. Calcium was adjusted to 6.3 g/kg in the basal diet which was heat-treated at 90 degrees C. Phytase was then added at 250, 500 and 750 FTU/kg diet. A negative control without added phytase was included (plant phytase <100 FTU/kg DM). The experiment comprised 10 treatments of 6 pigs (45 kg) kept in metabolism crates and fed one of the W diets for 12 days, 5 days for adaptation and 7 days for total collection of faeces. The P digestibility of the negative control was 31%, which increased significantly to 45, 50 and 53% when phytases were added at 250, 500 or 750 FTU/kg, respectively. The study showed the same efficacy for the fungal 3-phytase and the two bacterial 6-phytases on P digestibility at all three tested levels. The increase in P digestibility was greatest in the dosage range from 0 to 250 FTU/kg, while the increase was linear in the range between 250 and 750 FTU/kg. (C) 2010 Published by Elsevier B.V.