APPARENT DIGESTIBILITY AND RETENTION OF NUTRIENTS BOUND TO PHYTATE COMPLEXES AS INFLUENCED BY MICROBIAL PHYTASE AND FEEDING REGIMEN IN PIGS

Five barrows of approximately 45 kg BW, fitted with post-valvular T-cecum cannulas at the ileo-cecal junction, were assigned randomly to five treatments (5 x 5 Latin square design) to assess the effect of microbial phytase and feeding regimen (frequency and level) on the apparent digestibilities (total tract [ATTD] and ileal [AID]) and retention of nutrients. A corn-tapioca-soybean meal diet of low intrinsic phytase activity, containing no added inorganic P, was fed either without or with microbial phytase from Aspergillus niger var. Van Tieghem (800 phytase units/kg of diet) at different feeding frequencies (once, twice, or seven times per day) and feeding levels (2.3 vs 2.8 times the maintenance requirement for ME, i.e., 418 kJ ME/BW.75). Microbial phytase enhanced significantly the ATTD of DM, OM, CP, Ca, total P, and amino acids (except for cystine and proline). Also, the AID of total P, phytic acid, methionine, and arginine was increased (P < .05 or .01). As a consequence of adding this enzyme, the retention (grams/day) of N, Ca, and P was greater (P < .01) and their daily excretion was diminished by 5.5, 2.2, and 1.9 g/d, respectively. The feeding level exerted a minor effect on the ATTD and AID (except for methionine and cystine), although the retention (grams/day) of N, Ca, and P was greater ( P < .01) at the higher level of feeding. The feeding frequency influenced significantly the ATTD of Ca, tryptophan, and isoleucine and the AID of phytic acid, cystine, arginine, isoleucine, and phenylalanine. Also, N retention (grams/day) was reduced in pigs fed once daily (P < .01).