The impact of microbial muramidase (MMUR) addition to broiler chicken rations was evaluated through growth parameters, liver histoarchitecture, antioxidant status, biochemical analysis, and expression of pro-inflammatory cytokines for 35 days. Four hundred three-day-old chicks (97.68 ± 0.59 g) were distributed to four distinct groups with ten duplicates each (100 chicks/group) consisting of: group 1 (G1): a basal diet without MMUR (control group); G2: a basal diet + 200 mg MMUR kg-1 G3: a basal diet + 400 mg MMUR kg-1; and G4: a basal diet + 600 mg MMUR kg-1. The results showed that the final body weight and total weight gain were increased (p = 0.015) in birds fed with diets supplemented with MMUR at 600 mg kg-1. The feed conversion ratio (FCR) was improved in all treatment groups compared with the control group. Birds fed with a diet supplemented with 600 mg MMUR kg-1 showed the highest body weight gain and improved FCR. The values of thyroxin hormones and growth hormones were increased in all MMUR-supplemented groups. Dietary MMUR increased the activities of antioxidant enzymes (total antioxidant activity, catalase, and superoxide dismutase) and decreased the activity of malondialdehyde (p < 0.05). In addition, it increased the values of interleukin 1 beta and interferon-gamma compared with the control group. Furthermore, dietary MMUR increased the expression of transforming growth factor-beta immunostaining in the liver and spleen tissues. Our results show that supplementing broilers' diets with 600 mg MMUR kg-1 could enhance the chicken growth rate and improve their antioxidant, inflammatory, and anti-inflammatory responses.
Keywords: antioxidant enzymes; broiler chickens; growth performance; interleukin 1 beta; liver enzymes; microbial muramidase.