Effects of four feeding stimulants in high plant-based diets on feed intake, growth performance, serum biochemical parameters, digestive enzyme activities and appetite-related genes expression of juvenile GIFT tilapia (Oreochromis sp.)

The present research evaluated the effects of four feeding stimulants on feed intake (FI), growth performance, body composition, serum biochemical parameters, digestive enzyme activities and appetite-related gene expression for juvenile GIFT tilapia. Five experimental high plant-based diets (with 0, 0.4gkg(-1) dimethyl--propiothetin (DMPT), 0.6gkg(-1) dimethylthetin (DMT), 1.8gkg(-1) tryptophan (Trp) and 6gkg(-1) betaine (Bet), respectively supplemented) were fed to juvenile GIFT tilapia (Oreochromis sp.) (3.34 +/- 0.01g) for 8weeks. The results showed that FI was significantly increased by Trp and DMT. The highest specific growth rate (SGR) and protein efficiency ratio (PER) was observed for fish fed Bet diet, followed by DMT. Serum triglyceride was significantly increased by DMPT. Fish fed Bet diet showed significantly higher intestinal protease, liver protease and intestinal amylase activities. The neuropeptide Y (NPY) mRNA expression in brain was significantly improved by Trp, and ghrelin mRNA expression in stomach was significantly increased by DMT. It is concluded that supplementation of Trp or DMT could act as an effective feeding stimulants (FS) in high plant-based diets for juvenile GIFT tilapia, which might be associated with the relatively higher orexigenic (NPY or ghrelin) genes expression, and supplementation of Bet could improve SGR, PER and reduce feed conversion ratio (FCR) of juvenile GIFT tilapia.