Replacing fishmeal with cottonseed protein concentrate in feed for pearl gentian groupers (Epinephelus fuscoguttatus♀ × E. lanceolatus♂): Effects on growth and expressions of key genes involved in appetite and hepatic glucose and lipid metabolism

This study investigated the effects of replacing the fish meal (FM) in a 55 % FM fish feed with cottonseed protein concentrate (CPC) in pearl gentian groupers (Epinephelus fuscoguttatus♀ × E. lanceolatus♂). Effects on growth and the expression of key genes involved in appetite and hepatic glucose and lipid metabolism Four isoproteic and isolipidic diets were formulated containing 0 %, 6.06 %, 18.18 %, or 30.30 % CPC by replacing 0 % (FM, control), 10 % (CPC10), 30 % (CPC30), and 50 % (CPC50) of the FM in the feed, respectively. Each diet was fed to fish raised in triplicate groups for 56 days. No significant differences in specific growth rate, feed conversion ratio, or survival rate were found among dietary treatments. The weight gain in CPC groups was no different than in controls (P < 0.05). Fish fed the CPC50 diet had higher body lipid contents than others (P < 0.05) and the highest activity of hepatic fatty acid synthase, which was significantly higher than in group CPC10 (P < 0.05). The livers of CPC50 fish had significantly higher mRNA expression levels of apolipoprotein B-100, carnitine palmitoyltransferase 1, peroxisome proliferator-activated receptor α (PPARα), and PPARγ genes compared to other groups except CPC30 (P < 0.05). In conclusion, up to 50 % of the FM in fish feed can be replaced with CPC without adversely affecting the growth and feed utilization of pearl gentian groupers. However, 50 % replacement increased body lipid contents via modulation of hepatic lipid metabolism-related genes and enzyme activity.