In conclusion, use of herbal extracts specially garlic improved FCR comparable to virginiamycin in broilers. This effect could be attributed to improvement of digestive enzymes secretion. According to the obtained results in this study, it can be concluded that coneflower is not a suitable feed additive alternative for antibiotic as a growth promoter in broilers. Among the herbal extracts employed, coneflower and garlic were the most effective in immune function enhancement. Also these extracts were able to reduce the serum lipids. Improvement of selected intestinal bacterial populations through these extracts was remarkable. However, more trials are needed to clarify the effect of different medicinal plants on performance of broilers with regard to varied management conditions, including different stress factors, herbal extracts and their optimal dietary inclusion levels, active substances of extracts, dietary ingredients and nutrient content.