Purpose: To investigate the effect of phytosterol in a feed on growth and gene expression of broiler chickens.

Methods: Seven isonitrogenous diets with graded levels of polyhydroxy phytosterol(Castastesrone) (15, 20, and 25 g/kg diet) and hydroxyphytosterol (β-sitosterol) (25, 50, and 75 g/kg diet) were used to feed broiler chickens for 45 d.

Results: The dietary phytosterol significantly improved (p < 0.05) the body weight and feed intake of broiler chickens, especially with the 75 g/kg diet. In contrast, phytosterol supplementation was associated with significant (p < 0.05) hypotriglyceridemic effects with concurrent modifications of depressed antioxidant defence systems in the broiler chickens. Myogen, eIF4E, and S6k1 gene expression levels in tissues were significantly (p < 0.05)  improved by dietary phytosterol.  mTOR gene expression levels in muscle tissues were increased significantly (p < 0.05), but myostatin (GDF-8) and ubiquitin levels were significantly decreased (p < 0.05).

Conclusion: These results suggest that giving immediate phytosterol feeding regimen to chicks is a good feeding program for appropriate morphological development of the pectoralis major muscle and the expression of genes necessary for muscle cell proliferation and differentiation. Furthermore, the data suggest that developmental decline in skeletal muscle protein synthesis, may be partly attributed to developmental regulation of the activation of growth factor and nutrient components.