Effects of different levels of dietary protein and lipid on expression of genes involved in immunity (lysozyme and TNF- 1α) and appetite (ghrelin) of Zebrafish, Danio rerio

The present study was conducted to evaluate the effects of different levels of dietary protein and lipid on the expression of genes involved in immunity (lysozyme and TNF- 1α) and appetite (Ghrelin) in zebrafish, Danio rerio. So that, 9 diets with 3 protein levels (25, 30 and 35%) and 3 lipid levels (4, 8 and 12%) were prepared. One hundred and thirty five fish, 5 in each group, with an average weight of 1.23 ± 0.02 (g) were randomly distributed into 27 aquaria (20-liter) and fed 3 times daily during 4 months. A factorial experimental design was used for this study. The results revealed that the growth parameters (final weight, body weight gain, body weight gain percentage, specific growth rate and feed conversion ratio) and expression of immune and appetite genes increased significantly by increasing dietary protein levels in the treatment fed with 35% protein (p<0.05(. Increasing dietary lipid increased lysozyme expression and growth indices in fish fed with 12% lipid compared to other treatments; increased ghrelin gene expression in 12% compared to 4% significantly (p<0.05) and also insignificant increased TNF-1α expression (p>0.05). The combined effects of protein and lipid increased the lysozyme, TNF- 1α and ghrelin gene expression (p<0.05). The highest gene expression among all genes was observed in the diets containing 35% protein and 12% lipid. These findings revealed that dietary protein and lipid can enhance the function of immune system and appetite in zebrafish.