Effects of dietary Ca/P ratio, P level and microbial phytase supplementation on nutrient digestibilities in growing pigs: precaecal, post-ileal and total tract disappearances of OM, P and Ca

Eight female pigs (26-61 kg) provided with a simple T-cannula about 10 cm p roximal to the ileo-caecal valve, were used in two experiments to investiga te the effects of Ca/P ratio, P level and supplementation with phytase (500 FTU/kg) on precaecal, post-ileal and total tract disappearances of organic matter (OM), phosphorus (P) and calcium (Ca). In experiment 1, two Ca/P ra tios and two P levels were tested according to a 2 x 2 factorial arrangemen t within a Latin square design. In experiment 2, the diets of experiment I were supplemented with phytase (500 FTU/kg). There was a substantial absorp tion of OM, P and Ca in the post-ileal tract for all diets. Precaecal and t otal tract disappearances of OM were reduced by phytase addition (-4.1 and -0.8%, respectively). Supplementation with phytase resulted in an improveme nt of total tract and post-ileal P disappearances by 10.3 and 12.1%, respec tively, without affecting precaecal P disappearance. Addition of feed phosp hate resulted in a higher precaecal disappearance of P (+10.8%), resulting in a higher total tract disappearance of P (+5.9%). Addition of limestone h ad little effect on disappearances of OM, P and Ca, bur reduced activity of supplemental phytase and had a negative influence on growth performance. P recaecal, post-ileal and total tract Ca disappearances were hardly affected by the examined dietary factors. The results might indicate that P from fe ed phosphate is absorbed primarily prececally and that P From phytate, libe rated by microbial phytases, is dominantly absorbed post-illeally.