Hashim Al-Mudyir , Faris Alharbi , Yousef Alyousef and Gamal Rayan *
Animal and Fish Production Department, College of Agricultural and Food Sciences, King Faisal University, Al-Ahsa, 31982, Saudi Arabia
*Corresponding author: gahmed@kfu.edu.sa
Exogenous proteases are widely used in broiler nutrition to enhance protein digestibility and nutrient utilization; however, information regarding their dose-dependent effects and the relationships between protease supplementation and productive performance remains limited. This study evaluated the effects of graded levels of dietary protease supplementation on growth performance and the relationships among productive traits in Ross 308 broiler chickens. A total of 120 one-day-old chicks were randomly allocated to four dietary treatments containing 0, 200, 300, or 400 g of a commercial protease per ton of feed and were reared for 35 days. Growth performance data were analyzed using one-way analysis of variance (ANOVA) followed by Duncan's multiple range test, while Pearson correlation, graphical dose-response, and relative improvement analyses were performed to further characterize the productive responses to protease supplementation. Initial body weight did not differ among treatments (P = 0.1954), confirming uniform group allocation at the start of the experiment. Dietary protease supplementation significantly increased final body weight (P = 0.0058), whereas average daily feed intake was not significantly affected (P = 0.6166). Feed conversion ratio showed a consistent numerical improvement in all protease-supplemented groups compared with the control group. Graphical dose-response analysis demonstrated progressive improvements in productive performance with increasing dietary protease inclusion, while relative improvement analysis indicated that supplementation at 300–400 g/ton elicited the greatest productive response. Pearson correlation analysis revealed stronger positive associations between feed intake and final body weight, as well as stronger negative associations between final body weight and feed conversion ratio, at higher levels of protease supplementation, suggesting enhanced nutrient-utilization efficiency. In conclusion, dietary protease supplementation improved the productive performance of broiler chickens in a dose-dependent manner. Under the conditions of the present study, supplementation at 300–400 g/ton produced the most favorable productive responses, supporting the use of exogenous protease as an effective nutritional strategy to improve broiler production efficiency.