DIETARY PROTEIN AND LIPID ON GROWTH PERFORMANCE, BODY COMPOSITION AND DIGESTIVE ENZYME ACTIVITIES OF WINTERLING CULTER ALBURNUS ♀×MEGALOBRAMA TERMINALIS♂

After the aquaculture experiment is completed, the total weight and quantity of fish in each experimental tank are counted to calculate indicators such as growth and survival rate; Randomly select 4 experimental fish from each sink for routine nutritional composition determination of the entire fish; Take another 4 experimental fish and collect their dorsal muscles for routine nutritional composition determination; Another 8 experimental fish were taken to measure their body weight and length, respectively, for calculating their fullness; After dissecting 8 experimental fish on an ice plate, the viscera, liver, and intestines were separated, and the visceral, liver, and intestinal weights were measured for calculating body shape indicators. The nutritional composition of experimental feed, whole fish, and muscle, including water content, crude protein, crude fat, and ash, shall be carried out in accordance with the AOAC method [9]. The method for detecting intestinal digestive enzyme activity is as follows: after anesthesia of experimental fish (MS222, concentration 1:10000), 6 fish were randomly dissected and their intestines were separated on ice plates from each water tank. After removing fat blocks and contents, they were mixed into a sample and placed in a homogenization bottle. 10 times the weight of the intestines were added to a phosphate buffer (pH 7.4, NaCl 50 mmol/L, Na2HPO4- NaH2PO4 154 mmol/L) to prepare a homogenization solution, which was then centrifuged at 4 ° C and 10000 × g for 10 minutes to obtain crude enzyme solution. The protease activity was measured using the Folin reagent method [10], the amylase activity was measured using the Bernfeld method [11], the lipase activity was measured using the Nanjing Jiancheng Biotechnology Research Institute reagent kit, and the protein concentration in the crude enzyme solution was measured using the Coomassie Brilliant Blue method [12]. Calculate an average value for each breeding tank for statistical analysis.