Effect of dietary protein lowering and supplementation of peppermint extract on yield, carcass, blood parameters and microbial population of broiler chickens

Due to population growth and increasing demand for protein sources, poultry farming became industrialized. This has increased the density of breeding per unit area and also increased the likelihood of disease in them. However, the spread of diseases has led to a greater tendency to use antibiotics. Therefore, one of the ways to reduce the use of antibiotics is to use medicinal plants, such as mint. Therefore, an experiment was performed to investigate the effects of reducing dietary protein levels and adding peppermint extract on the performance of male Ross 308 broilers.

An experiment was conducted in a completely unbalanced random design with 2×2 factorial methods with four treatments, four replications and 10 chickens per replication. Experimental diets include: a) control diet with standard protein and without peppermint extract, two) control diet with three tenths percent of peppermint extract diet, three) low protein diet without peppermint extract, four) low protein diet with the addition of three tenth percent of the ration was peppermint extract. During the experiment, the birds' performance was evaluated periodically, blood parameters, immune response, meat quality, microbial population and carcass characteristics.

During the growing period and the whole breeding period, feed consumption and weight gain in the treatment containing low protein diet with peppermint extract increased significantly compared to the treatment with low protein diet without peppermint extract. The lowest feed conversion ratio was observed in the growing, final and whole growing years in the control treatment containing peppermint extract. Also the lowest percentage of Abdominal fat belonged to the control treatment containing peppermint extract (p<0.05). At 21 and 42 days of age, the lowest level of triglyceride was observed in the control treatment with 0.3% peppermint extract (p<0.05). In this experiment, meat malondialdehyde concentration and microbial population were not affected by experimental treatments.

The results of this experiment showed that adding peppermint extract to the diet from the growing period can improve yield.