The effect of microbial phytase on true and apparent ileal amino acid digestibilities in growing-finishing pigs.
Ten 56-d-old, 15-kg barrows were surgically fitted with a postvalvular T-cecum cannula at the ileo-cecal junction to evaluate the effect of microbial phytase on apparent and true ileal AA digestibility and N utilization. A semipurified cornstarch- and soybean meal-based diet was formulated to contain 3.4 Mcal of DE/kg, 17.0% CP, 0.8% Ca, and 0.6% P but had a low phytate-P concentration (0.13%; all on an as-fed basis). Chromic oxide and dysprosium chloride were used as indigestible markers. The basal diet was supplemented with 0 or 1,000 phytase units/kg of microbial phytase. Postprandial plasma urea N and alpha-amino N concentrations, excretion of Ca, P, and N in feces and urine, and ileal AA digestibilities were determined 3 times at 4-wk intervals beginning at 70 d of age. The homoarginine (HA) method was used to determine endogenous AA flow by replacing 50% of the basal protein with guanidinated protein. Microbial phytase had no effect on apparent ileal digestibility (AID) or on true ileal digestibilities of N and most AA but did increase AID for arginine (P = 0.006) and methionine (P = 0.037). However, in HA diets, phytase increased the AID of CP (P = 0.01) and several AA. Addition of microbial phytase had no effect on the postprandial alpha-amino N concentrations in plasma but increased overall plasma urea N concentrations (P = 0.035). Barrows fed phytase-supplemented diets had decreased P in feces (P = 0.003) and greater P in urine (P = 0.001) but comparable total P excretion compared with barrows fed no phytase-supplemented diets. In conclusion, the addition of phytase to a semi-purified soybean meal-based diet did not affect the AID of several AA. In addition, differences between the basal and HA diets in N digestibilities indicated that that guanidination may limit the use of the HA method in determining endogenous protein losses.
Pomar
C
C
Agriculture and Agri-Food Canada, Sherbrooke, Québec, Canada.
Gagné
F
F
Matte
J J
JJ
Barnett
G
G
Jondreville
C
C
D010832:6-Phytase / Q000378:metabolism / Q000494:pharmacology*; D000596:Amino Acids / Q000097:blood / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000652:urine; D004063:Digestion / Q000187:drug effects; D005243:Feces / Q000737:chemistry; D006709:Homoarginine / Q000378:metabolism; D007082:Ileum / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009584:Nitrogen / Q000097:blood / Q000378:metabolism* / Q000652:urine; D010758:Phosphorus / Q000652:urine; D011897:Random Allocation; D013552:Swine / Q000378:metabolism* / Q000652:urine
D000596:Amino Acids; D006709:Homoarginine; D010758:Phosphorus; D010832:6-Phytase; D009584:Nitrogen; D002118:Calcium