This experiment was carried out to evaluate different levels of peppermint (Mentha piperita) plant powder usage on feed conversion ratio (FCR), body weight (BW), feed intake (FI), body temperature, carcass parts (breast and thigh) and internal organs (liver, heart, gizzard) weights in broiler chicken. A total of 192 broiler chicken were randomly divided into 4 experimental treatments with 4 replicates (12 birds per replicate) arranged in a completely randomized design. Experimental diets consisted of: (1) basal diet (control); (2) basal diet + 1% peppermint powder; (3) basal diet + 2% peppermint powder and (4) basal diet + 300 mg of vitamin E per kilogram. Heat stress performed by setting room temperature on 34 °C for 8 hours/day from 35 to 42 days of age. Results showed peppermint powder supplement in all levels significantly affected the FCR at 21 days of age and BW at 42 days of age (P<0.05). Birds treated by basal diet plus vitamin E and control diet showed the highest and lowest FCR values, respectively, at 21days of age. Body weight and feed consumption were significantly reduced in birds in the heat stress group. Peppermint powder supple-mentation at the level of 1% reduced body temperature compared with the control group during heat stress period (P<0.05). Significant differences were observed between dietary treatments for the relative weights of carcass, breast and thigh at 35 days of age and breast, gizzard and liver relative weights at 42 days of age (P<0.05). Birds fed basal diet plus vitamin E had higher carcass weight than the control groups on 35 days. In general, the results of this study revealed that peppermint powder as a natural antioxidant has beneficial effects on chicken growth performance, body temperature regulation and carcass and internal organ weights.

Keywords