Effect of peppermint (Mentha piperita L.) in broiler chicken diet on production parameters, slaughter characteristics and gut microbial composition

This study was conducted to evaluate the productive performance, carcass quality and cecal microbial composition of broiler chickens fed diets supplemented with different concentrations of peppermint powder. Peppermint (Mentha piperita L.) is characterized by strongly scented leaves. It is used as a remedy in herbal medicine, and consists of up to 4% essential oil (with 3545% menthol). The study included 960 one-day mixed-sex Ross 308 broilers. The chickens were assigned to 4 treatments and were housed in 24 boxes, with 6 replicates per treatment. Broilers received three diets (starter, grower and finisher) differing in the amount of supplemental peppermint powder, and were fed ad libitum. The diets contained different levels of supplemental peppermint powder: control group (C) - without peppermint, 02P - 0.2% peppermint, 04P - 0.4% peppermint, and 06P - 0.6% peppermint. The body weight of chickens was measured when changing their feed (days 10 and 24) and at the end of the experiment (day 42). Average feed intake, average daily gain, mortality, feed conversion, and the European Production Efficiency Factor (EPEF) were determined. At the end of the trial, 12 broilers of both sexes were randomly selected from each group and slaughtered to measure their carcass traits. Positive effects of peppermint supplementation were identified. The 04P chickens had significantly higher (p<0.01) values of average daily gain, feed conversion and EPEF compared with the C broilers. There were no significant differences in slaughter results (dressing percentages, the proportions of breast, drumsticks, thighs, wings, abdominal fat, heart, liver and stomach). The total numbers of aerobic bacteria and Lactobacilli were not affected by the peppermint supplementation into broiler diet. The Escherichia coli count in the 04P and 06P birds was lower than that in the C broilers (p<0.05). The results showed that the supplementation of 0.6% peppermint powder to broiler diet had positive effects on weight gain, feed conversion and cecal microbial composition.