The objective of the study was to evaluate the impact of various concentrations of orange (Citrus sinensis) peel meal (OPM), with or without the supplementation of multi-enzymes, on the growth performance, nutrient digestibility, antioxidant properties, and blood metabolic profile of broiler chickens. The experiment was conducted on 240 one-day-old Arbor Acres broiler chicks, assigned to eight dietary treatments with 30 broilers per treatment group. Four dietary orange peel meal (OPM) concentrations were supplemented, namely, the control (without OPM), and with 80, 160, and 240 g/kg of the diet. To each of these diets was added two concentrations of multi-enzyme inclusion (0 or 0.6 g as a combination of 0.5 g of Nutrikem and 0.1 g Optiphos per kg diet) in a completely randomized design in a 4 × 2 factorial arrangement. The experiment lasted until 42 days of age. Body weight gain (BWG) was influenced during the grower period (22-42 days) and the overall period (0-42 days), and the feed conversion ratio (FCR) was significantly improved by supplementations of OPM compared with the control for 22-42 days and overall (0-42 days) periods. Moreover, BWG, FCR during the grower and overall periods, and crude fiber digestibility were improved (p < 0.01) by multi-enzyme supplementation compared to the non-supplemented groups. Broilers with diets supplemented with OPM had considerably lower abdominal fat (p < 0.01) than the control. In addition, when compared to the non-supplemented enzyme group, serum T3 and T3/T4 ratios were significantly improved in response to enzyme addition. When compared to the control group, superoxide dismutase (SOD) was significantly higher in the OPM groups, showing the largest improvement in antioxidant response. Interaction effects were observed only for serum SOD levels. Based on our findings, it is recommended that OPM be used as a feed supplement for raising broilers, and adding 0.6 m g/kg of multi-enzymes could provide additional benefits to the performance of broilers.
Keywords: antioxidants; blood biochemistry; broiler chicken; feed additives; performance; sustainability.