Evaluation of the Antioxidant Status of Ethanolic Extract of <i>Hypericum perforatum</i> and Its Effect on Performance, Immune System, Antioxidant Status and Plasma Biochemical Indices of Broiler Chickens

BACKGROUND: Plant extracts contain bioactive compounds that have positive effects on the immune response and antioxidant system in living cells. St. John's wort (Hypericum perforatum) is a medicinal plant that contains hypericin, hyperforin and pinene, which have antiviral, anti-inflammatory, antimicrobial and immune stimulating effects. OBJECTIVES: This experiment was conducted to evaluate the antioxidant activity of Hypericum perforatum ethanolic extract (HPEE) and its effect on growth performance, abdominal fat, immune response and blood biochemical indices of broiler chicks. METHODS: A number of 200-day-old male Ross-308 broiler chickens were randomly assigned to four treatments with five replications and 10 birds each. Dietary treatments included 0, 150, 300 and 450 mg/kg HPEE. Body weight, feed intake and feed conversion ratio were recorded in broiler chickens during the starter (0-10 days of age), grower (11-24 days of age) and finisher (25-42 days of age) periods. To evaluate antioxidant activity, immune system, blood biochemical traits and relative weight of visceral and lymphatic organs, two birds from each replicate were sacrificed and blood was gathered at 24 and 42 days of age. RESULTS: Dietary treatments did not affect growth performance including feed intake, body weight and feed conversion ratio. On Day 24, the relative weight of abdominal fat in birds fed HPEE was reduced compared to the control (p < 0.05). Relative crop weight increased in birds fed the 450 mg/kg HPEE, compared to the control diet on Day 24 (p < 0.05). The lowest concentration of malondialdehyde (MDA) was observed in 450 mg/kg HPEE, which was significantly lower than control (p < 0.05). In addition, HPEE increased the total antibody titer and IgM titer against sheep red blood cells (SRBC), compared to control (p < 0.05). Blood indices including cholesterol, LDL and glucose were reduced by HPEE diets at 42 days. HPEE caused a decrease in plasma aspartate aminotransferase (AST) enzyme activity. CONCLUSION: HPEE supplementation in broiler diets can improve the immune system and may reduce abdominal fat, serum AST, alanine aminotransferase (ALT) enzyme activities and MDA concentration in broiler chickens, without having an adverse effect on growth performance and carcass characteristics of broiler chickens.