LAUSR

Abstract This study investigated whether dietary supplementation of phytogenic compounds limonene and thymol had synergistic or additive effects on growth and selected nutritional physiology pathways in Nile tilapia. A 63-day feeding experiment was conducted using fish of 1.5 ± 0.0 g (± standard error) fed on a commercial diet coated with either 0 ppm limonene and thymol (control), 400 ppm limonene (L), 500 ppm thymol, (T) or a combination of 400 ppm limonene and 500 ppm thymol (LT). Final fish weight (FW) was significantly improved to similar extents by diet LT (16.7 ± 0.3 g) and L (16.6 ± 0.4 g). Dietary thymol alone and the control did not enhance FW (15.0 ± 0.4 g and 13.7 ± 0.4 g respectively). Dietary thymol had shown a strong tendency to improve somatic growth (P = .052). The analysed candidate genes involved in the pathways of nutrient digestion, absorption and transport (muc), lipid metabolism (lpl), antioxidant enzymes (cat) and somatotropic axis growth (igf I) were also up-regulated to similar extents in Nile tilapia by diet L and LT (P