Abstract
Background:
Growing populations around the world are driving up the demand for broilers, so the poultry industry must maintain standards for food safety and quality. The threat of antibiotic resistance to health has prompted the adoption of organic feed additives aimed at boosting immunity and production.

Aim:
This study aimed to evaluate the influence of peppermint leaf and stem powder on broiler growth, meat quality, blood biomarker indices, liver, and antioxidant enzyme activities.

Methods:
At one day of age, 360 unsexed broiler chicks of the Ross 308 strain were used in the study. The birds were allocated into six groups, each with 60 birds, and each group had three replicates (20 birds per replicate). The first group served as a positive control, receiving a basal diet supplemented with antibiotics and antioxidants (PC), and the second group was a negative control (NC), consisting of birds that received only a basal diet. Peppermint powder (Pep) was added at four different levels (0.15%, 0.30%, 0.45%, and 0.60%) to the basal diet in the remaining four treatments.

Results:
The addition of Pep improved growth performance significantly (P < 0.05), according to statistical analysis. In particular, the addition of Pep at a level of 0.60%/kg diet resulted in the highest body weight gain (2058.1g) and lowest FCR (1.43) compared to other treatments. Moreover, Pep treatments significantly decreased (P < 0.05) total cholesterol, triglycerides, and low-density lipoprotein (LDL) levels by 135.6, 116.39, and 45.03 mg/dL, respectively, whereas high-density lipoprotein (HDL) levels were significantly increased (110.10 mg/dL). In addition, all Pep treatments reduced the levels of liver enzymes aspartate aminotransferase (AST), alkaline phosphatase (ALP), and alanine aminotransferase (ALT) to 92.60, 2.49, and 111.21 U/dl, respectively, and led to a significant improvement (P < 0.05) in antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPX), especially when Pep was used at 0.45% and 0.60%.

Conclusion:
Using Pep as a natural feed additive improves the growth performance traits (weight gain, FI, FCR, and carcass traits) and blood profile of broilers. In addition, it is a natural alternative to synthetic antibiotics and antioxidants.

Key words: Phytogenic feed additives; Antioxidants; Blood characteristics; Broiler performance; Peppermint.