Effects of formulated diet and fresh frozen Hypophthalmichthys molitrix on growth, plasma biochemical index and antioxidant ability and histology of Micropterus salmoides

To study the effects of different origins of feed on growth, plasma biochemical indexes, antioxidant capacity, liver and intestinal histology of Micropterus salmoides, 180 largemouth basses initial average weight (12.45±0.07) g were randomly divided into 2 groups with three replicates at a stock density of 30, and commercial compound diet and fresh frozen Hypophthalmichthys molitrix were allocated to each of two groups of fish for a feeding period of 84 days. Results suggest that group with commercial compound diet behaves significantly lower than the other group on weight gain rate(WGR), specific growth rate (SGR) and feed conversion ratio (FCR), with the same conclusion on the liver protease activities. And the former performs higher than the latter on protein efficiency ratio (PER), hepatosomatic index (HSI) and viscerosomatic index (VSI) than the other group, similar to the hepatic glycogen contents. But significant difference disappeared in muscle glycogen and intestinal amylase activities between 2 groups. The AST activities, glucose (GLU) and MDA contents and Ca/P ratio of largemouth basses fed with commercial compound diet are significantly higher than those fed with fresh frozen trash fish group, but the activities of ALP, SOD, GSH-Px and the contents of TP, TG, UREA, Ca, P in plasma are significantly lower than fresh frozen trash fish group. No significant difference was observed in ALT, TC and insulin contents of plasma among all groups. The histological study showed that ultrastructure of the liver and the intestine in the commercial compound diet treatment were abnormal. Serious vacuolization in liver, the severe mechanical damage of intestinal villi were found in commercial compound diet group. The study, under given conditions, indicates that fresh frozen H. molitrix is more appropriate to feedM. salmoides compared with commercial compound diet. The latter not only affected the growth of largemouth bass but also did harm to the liver and intestine of largemouth bass. Therefore, feed formulation technology for largemouth bass could be further developed, referring to nutritional composition of fresh frozen H. molitrix and the metabolic properties.