The influence of ghrelin and des-ghrelin on feed intake, growth performance and hypothalamic NPY mRNA expression of grouper Epinephelus coioides

This experiment was conducted to investigate the effect of ghrelin and des-ghrelin on feed intake, growth performance and hypothalamic neuropeptide Y (NPY) mRNA expression of grouper, Epinephelus coioides. Ghrelin and des-ghrelin (non-acylated form) were supplemented in the basal diet at the dose of 0, 2, 4 mg kg− 1. The highest feed intake, weight gain (WG, %) and final body weight (FBW, g) were recorded when ghrelin was added at the dose of 4 mg kg− 1 and they were significantly different from that of the control (P < 0.05). Compared to the control group, no significant (P > 0.05) effect on growth performance and feed intake was observed in fish fed diet supplemented with des-ghrelin at 2 and 4 mg kg− 1. There were no significant differences (P > 0.05) in the proximate composition (crude protein, crude lipid, ash and moisture), slaughter variables (condition factor, viscerasomatic index, hepatosomatic index and intraperitoneal fat ratio) and serum lipid (total cholesterol, triglyceride, low density lipoprotein and high density lipoprotein) in fish fed all the test diets. Grouper hypothalamic NPY mRNA expression was significantly (P < 0.05) increased when ghrelin (2, 4 mg kg− 1) was supplemented in the diet. However, grouper fed the diet added with des-ghrelin (2, 4 mg kg− 1) did not show an increase (P > 0.05) in the expression of hypothalamic NPY mRNA. The present results indicated for the first time that ghrelin supplemented in the diet could stimulate feed intake, growth and hypothalamic NPY mRNA expression of grouper, while des-ghrelin did not have those effects.

► Ghrelin supplemented in the diet stimulated feed intake and growth of grouper. ► Actions of ghrelin on grouper appear to mediate through NPY neuronal pathway. ► Des-ghrelin showed no effects on FI, WG and NPY mRNA expression of grouper.