The effects of five blends of medicinal plants on performance, carcass characteristics, humoralimmunity and serum lipids of broiler chickens were studied in this experiment. A total of 304 day- oldmale Ross-308 broiler chicks were allocated into six dietary treatments including basal diet with nosupplement as control group (C), basal diet plus 10 g/kg of herbal blends including; garlic, cinnamon,thyme, rosemary and anise (B), thyme, caraway, carum copticum (G), alfalfa, senna, corn flower and absinthe (D) alfalfa, liquorice root, great burdock, cinnamon (F), polygermander, water cress, absintheand echinacea purpura (E). Live body weight (LBW), average daily gain (ADG), daily feed intake (DFI), feed conversion ratio (FCR), carcass characteristics, concentration of some serum metabolites,immunological properties such as antibody titer against Newcastle disease virus as well as relativeweights of bursa gland and spleen were studied in the experimental birds. Addition of blend D to thediet resulted in insignificant improvement of LBW whereas blend E decreased the birds LBW whencompared with control group (p < 0.05) at 21 and 42 days of age. Significant depression of ADG in 1-21and 1-42 and higher FCR in 1-42 rearing periods were also recorded in the blend E treated chickens (p <0.05). The birds DFI were not affected by the experimental diets. Higher cholesterol contents of serum in B, F and G groups at day 33 and lower TG and VLDL contents at day 21 of age were noticeable changesin to the measured serum metabolites (p < 0.05). The addition of 10 g/kg blend F to the broiler dietresulted in the most consistent improvement in antibody titer against Newcastle disease virus (p < 0.05) among the groups. Lower carcass yield was documented in the administration of blend E in broiler diet than control and D treated birds (p < 0.05). The supplemented medicinal plants used in this study did not create significant enhancement in broiler bird's performance; however, some improvement
