Effects of replacing fish meal with compound proteins on the growth, body composition and biochemical indices of hybrid snakehead

This experiment was conducted to study the effect of replacement of fish meal by compound protein (fermented rapeseed meal+cotton meal+silkworm pupae+mulberry leaves) on the growth, body composition, antioxidant ability and biochemical indices of hybrid snakehead with the initial weight (22 g). Five isonitrogenous and isolipid diets (CP 42%, EE 8.5%) were formulated to contain different levels of compound proteins based upon the basal diet to replace fish meal 0%, 12%, 24%, 36% and 48%. After 8 weeks, the results showed as follows: when the replacement ratio of fish meal by compound protein is more than 12%, the final body weight (FBW) and the specific growth rate (SGR) were significantly decreased, and reached a minimum at 48% substitution level. A lower protein efficiency ratio (PER) and higher feed conversion ratio (FCR) were observed at the 36% and 48% substitution levels. There is no significant difference in feeding rate (FR) for each test group. The replacement level of compound proteins decreased significantly body crude lipid, viscera somatic index (VSI) and intraperitoneal fat ratio (IPF), and increased significantly whole body moisture. With the compound protein level increasing, the activity of trypsin decreased significantly, whlie the activity of intestinal lipase increased significantly. When the compound protein level is higher than 24%, the activities of glutamyl pyruvic transaminase (GPT), superoxide thandismutase (SOD) and the catalyse (CAT) activities significantly increased. Serum CHO was decreased observably as compound protein ratio is more than 12%, but blood glucose content was decreased observably as compound protein ratio is more than 36%.There were no significant difference in total cholesterol (TC), total protein (TP) and albumin (ALB) for each test group. Results of above show that a suitable percentage (12%) of compound protein replacement of fish meal does not affect the growth of hybrid snakehead. And high replacement level would inhibit the growth of hybrid snakehead, but it can improve the glucolipid metabolism and antioxidant capacity of hybrid snakehead.