Effect of dietary carbohydrate-to-lipid ratios on growth performance, body composition, nutrient utilization and hepatic enzymes activities of herbivorous grass carp (Ctenopharyngodon idella)

Abstract

Six isonitrogenous (390 g kg )1 ) and isoenergetic (16.2 kJ g )1 ) diets with varying carbohydrate : lipid (CHO : L) ratios (202.5-1.74), were fed to triplicate groups of 25 fish in indoor recirculation system. Over 8-week-growth trial, best weight gain (WG), specific growth rate, feed conversion ratio, protein efficiency ratio and protein production value (P < 0.05) were observed in fish-fed diets with CHO : L ratio of 7.5. Fish fed either the lowest (1.7) or highest (202.5) CHO : L ratio tended to produce lower (P < 0.05) growth and feed conversion efficiencies. The values of viscerosomatic index, hepatosomatic index and intraperitoneal fat ratio increased as dietary CHO : L ratios decreased. There were no significant differences in whole body and liver crude protein among dietary treatments. Whole body and liver lipid increased as CHO : L ratios decreased. Plasma cholesterol and triacylglyceride levels increased linearly as dietary CHO : L ratios decreased. Activities of glucokinase and pyruvate kinase were stimulated by elevated levels of dietary carbohydrate; however, activities of lipase (LPS) and alkaline phosphatase were stimulated by elevated levels of dietary lipid. Based on a second-order polynomial regression analysis of WG against dietary carbohydrate and lipid levels, 275 g kg )1 of carbohydrate and 59 g kg )1 of lipid, corresponding to a CHO : L ratio of 4.7, in a diet holding 390 g kg )1 of crude protein and 16.3 kJ g )1 of gross energy, proved to be optimal for grass carp. These results indicated that utilization of dietary lipid and carbohydrate was moderate in grass carp, but the fish were a little more capable of utilizing lipid compared with carbohydrate. KEY WORDS

Transcriptomic and Metabolomics Analyses Show that High Carbohydrate Induces Fatty Liver in Blunt Snout Bream (<em>Megalobrama amblycephala</em>)<strong></strong>

“…These references reported that high carbohydrate had no significant effect on growth performances. In contrast, other research reported that excessive carbohydrate levels had effect on growth performances by reducing the growth rate, and increasing FCR in blunt snout bream [23] and grass carp (Ctenopharyngodon idellus) [24]. The reason of difference from our result may be related to the different carbohydrate content in different diets.…”

Fasted and postprandial response of serum physiological response, hepatic antioxidant abilities and HSP70 expression in Wuchang bream (Megalobrama amblycephala) fed different dietary carbohydrate levels

“…Similar findings were obtained in top mouth culter (Erythroculter ilishaeformis Bleeker) (Liu et al, 2008) and European whitefish (Coregonus lavaretus) (Vielma et al, 2003). However, some other studies reported no significant differences in gilthead sea bream (Sparus aurata) (Enes et al, 2008), largemouth bass (Micropterus salmoides) (Amoah et al, 2008) and grass carp (Ctenopharyngodon idellus) (Gao et al, 2010).…”

Nutritional regulation of glucokinase: a cross-species story

“…More surprisingly, the induction of GK activity by carbohydrates is lower in omnivorous fish known to utilise carbohydrates well, i.e. common carp (164,211) , Indian carp (Catla catla) (212) , silver sea bream (Pagrus auratus) (213) , zebrafish (Danio rerio) (214) , tilapia (Oreochromis niloticus x O. aureus) (215) and grass carp (Ctenopharyngodon idella) (216) . This suggests that induction of hepatic GK is not a limited factor to use dietary carbohydrates.…”