GROWTH PERFORMANCE, FATTY ACID COMPOSITION, AND LIPID METABOLISM IN JUVENILE HYBRID STURGEON (ACIPENSER SCHRENCKII BRANDT♀×A. BAERI BRANDT♂) FED DIETS OF FISH OIL SUBSTITUTED BY VARIOUS LEVELS OF LINSEED OIL

A 12-week experiment was performed using juvenile hybrid sturgeon (70.8±0.5) g to study the effects of partial and total replacement of fish oil (FO) by linseed oil (LO). Five isonitrogenous (38.7% crude protein) and isoenergetic (10.0% crude lipid) experimental diets were formulated as follows: LO0 (100% FO); LO25 (75%FO+25% LO); LO50 (50% FO+50%LO); LO75 (25%FO+75%LO); and LO100 (100%LO). These diets were fed to triplicate groups of 40 hybrid sturgeon three times a day to apparent satiation at (22±1.0)℃. There were no significant differences in final body weight, weight gain rate (WGR), and specific growth rate (SGR) in all fish groups (P>0.05). Fish fed diets with LO0, LO25, and LO50 had significantly higher feed intake than fish fed diets with LO75 and LO100 (P<0.05). Fish fed diets with LO100 had significantly higher feed efficiency than fish fed a diet with LO0 (P<0.05). Fillet and liver lipid content, and serum lactate dehydrogenase (LDH), glutamic-oxalacetic transaminase (ALT) and glutamic-pyruvic transaminase (AST) activity showed an increasing trend as linseed oil increased (P<0.05). The linolenic acid (C18:3n3) content, the sum of n-3 and n-6, and the n-3:n-6 ratio in fillets showed a positive linear correlation with the diets. Lipid metabolism throughout the day for sturgeon on different levels of linseed oil replacement showed that the lipid source and time point, and the interaction of both of these factors had significant effects on serum non-esterified fatty acid (NEFA), triglyceride (TG), High-density lipoprotein cholesterol (HDL-Chol), and low-density lipoprotein cholesterol (LDL-Chol) (P<0.05). Serum total cholesterol and ketone bodies were not affected by the lipid source, time point, or interaction of both factors (P>0.05).