Influence of feeding level and dietary oil supplementation on apparent ileal and total tract digestibilities of phosphorus and calcium in pigs fed low-phosphorus diets supplemented with microbial or wheat phytase

Two experiments were conducted with pigs fitted with simple T-cannulas at the distal ileum to evaluate the effect of energy (ME) intake implemented by variation of feeding level (FL) (exp. 1) or dietary plant oil content (exp. 2), on apparent ilea] (AID) and total tract digestibilities (ATTD) of phosphorus (P) and calcium (Ca), including measurements of lower myo-inositol phosphates at the ileal and fecal level. In exp. 1, 14 barrows (BW 7.3 kg) were fed one of two low-P corn-soybean meal diets providing either 600 U kg(-1) microbial (Natuphos (R) 5000 G) or native wheat phytase at two FL (2.0 vs. 2.8 x ME maintenance requirement) according to a two-period cross-over design: The AID and ATTD of P and Ca were higher (P < 0.05) in pigs fed microbial phytase compared with wheat phytase. Furthermore, the recoveries of lower myo-inositol phosphates in the feces, but not in the ileal digesta, were higher (P < 0.05) when microbial instead of wheat phytase was added to the diet. Increasing the feed intake improved (P < 0.05) overall AID and ATTD, of P, independent of the origin of the supplemental phytase. Additionally, the increase in FL improved (P < 0.05) AID of P in pigs fed wheat phytase. There was no effect (P > 0.05) of FL on ilea] or fecal recovery of myo-inositol phosphates. In exp. 2, eight barrows (BW 20.3 kg) were fed a low-P corn-soybean meal diet providing 600 U kg-1 microbial phytase (Natuphos (R) 5000 G) supplemented without or with 6% plant oil according to a two-period cross-over design. There was no effect (P > 0.05) of oil supplementation on AID and ATTD of P or Ca. In conclusion, an increase in FL improves AID and ATTD of P in pigs fed diets supplemented with microbial or wheat phytase, while increasing energy density had no effect.