Submitted to: Fish Physiology and Biochemistry Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/10/2001
Publication Date: 12/10/2001
Citation: RICHE, M.A., TROTTIER, N.L., PAO, K., GARLING, D.L. APPARENT DIGESTIBILITY OF CRUDE PROTEIN AND INDIVIDUAL AMINO ACIDS IN TILAPIA (OREOCHROMIS NILOTICUS) FED PHYTASE PRETREATED SOYBEAN MEAL DIETS.. FISH PHYSIOLOGY AND BIOCHEMISTRY JOURNAL. 2001. v.25. p.181-194. Interpretive Summary: Soybeans contain components that can reduce the amount of nutrients available to animals. One of these components, phytic acid, is known to decrease digestibility of amino acids in the diet. Evidence in some species suggests the removal of phytic acid increases amino acid digestibility from the diet. Two groups of tilapia (Oreochromis niloticus) were fed diets with increasing levels of soybean meal. One group was fed diets containing unmodified soybeans; the other group was fed diets containing soybeans from which phytic acid was removed. The results suggested two amino acids, methionine and lysine, were less digestible in the diets containing soybeans without phytic acid. Unlike some other species where removal of phytic acid is beneficial, the removal of phytic acid from soybeans appears to be detrimental to tilapia.
Technical Abstract: Soybeans contain phytates, the anionic forms of 1,2,3,5/4,6- hexakis (dihydrogen phosphate) myoinositol, with the potential to reduce amino acid (AA) availability. Tilapia lack the intestinal enzyme phytase to hydrolyze phytates. Oreochromis niloticus (approximately 68 g) were fed diets containing either phytase pretreated or untreated soybean meal (SBM) incorporated at 0, 25, 50, 75, or 100 % of the crude protein (CP) in a 33 % CP diet to determine whether phytates reduce CP and amino acid digestibility. There were no differences in apparent CP digestibility. Dietary and digestible methionine (Met), and digestible lysine(Lys), decreased with increasing incorporation of phytase pretreated SBM. Reduced digestibility of Met and Lys from the phytase pretreated diets was likely due to removal of phytates. Phytates may reduce the effect of other antinutritional factors, protect amino acids from degradation, or decrease leaching of water soluble components.