Effects of Neutral Phytase Supplementation on Biochemical Parameters in Grass Carp, Ctenopharyngodon idellus, and Gibel Carp, Carassius auratus gibelio, Fed Different Levels of Monocalcium Phosphate

Two 8-wk studies were conducted to evaluate the effects of neutral phytase supplementation on hemato-biochemical status, liver biochemical parameter, and intestinal digestive enzyme activity of grass carp, Ctenopharyngodon idellus, and gibel carp, Carassius auratus gibelio, fed with different levels of monocalcium phosphate (MCP). The control diet was prepared with 2% MCP but without phytase (P2.0). The other three experimental diets were prepared with the addition of 1.5, 1.0, and 0.5% MCP, respectively, when supplemented with 500 U/kg neutral phytase in each diet and designated as PP1.5, PP1.0, and PP0.5, respectively. The results indicated that the serum alkaline phosphatase (ALP), alanine transaminase (ALT), and aspartate transaminase (AST) activities, as well as the albumin (ALB) content were increased in grass carp (P < 0.05) and gibel carp (P > 0.05) fed with phytase-supplemented diets. Meanwhile, the serum cholesterol, high-density lipoprotein, and total protein contents of the two species of fish were increased in comparison to the control. In addition, dietary phytase inclusion did not significantly affect hepatic ALP, ALT, and AST activities in the two species of carp fed with different levels of MCP. Amylase activity increased in foregut and hindgut of both species when fed with the phytase-supplemented diets while lipase activity was reduced in the foregut and hindgut in both fish. This study suggests that neutral phytase supplementation increases serum ALP, ALT, and AST activities but does not notably affect these enzyme activities in the liver of the two species of carp when fed different levels of MCP. On the other hand, amylase activity increased while lipase activity was reduced in the intestine of the species of carp fed with phytase-supplemented diets.