Functional Evaluation of Pomegranate (Punica granatum) Juice Byproducts as Dietary Additives in Red Seabream (Pagrus major): Effects on Growth Performance, Antioxidant Response, Immunity, and Resistance to Edwardsiella tarda.

Abstract

This study evaluated the potential of pomegranate (Punica granatum) juice byproducts (PJB) as a functional dietary additive for juvenile red seabream (Pagrus major). Four experimental diets were formulated to contain various levels of PJB (0, 2.5, 5.0, and 10.0 g/kg) and fed to fish with an initial body weight of 7.0 ± 0.01 g for 8 weeks. Growth performance, feed utilization, digestive enzyme activity, whole-body composition, plasma biochemical parameters, antioxidant responses, immune parameters, and resistance to Edwardsiella tarda infection were evaluated. Fish fed the diet containing 2.5 g/kg PJB exhibited significantly higher final body weight, weight gain, and specific growth rate compared with the control group and those with higher PJB doses, whereas feed intake, feed efficiency, and protein efficiency ratio were not significantly affected by dietary treatment. Intestinal trypsin and lipase activities were significantly elevated in the PJB2.5 group, whereas amylase activity remained unchanged. Whole-body proximate composition and plasma biochemical parameters, including aspartate aminotransferase, alanine aminotransferase, total cholesterol, glucose, and total protein, were not significantly influenced by dietary PJB supplementation. Dietary inclusion of PJB at 2.5 g/kg also significantly enhanced plasma antioxidant enzyme activities, as evidenced by increased superoxide dismutase and glutathione levels, while catalase activity was elevated in fish fed the PJB2.5 and PJB5 diets. Innate immune responses were also stimulated, with significantly higher serum lysozyme activity and interleukin-1 levels observed in fish fed the PJB2.5 diet. Following experimental challenge with E. tarda, fish fed diets containing 2.5 and 5.0 g/kg PJB exhibited significantly higher cumulative survival than the control group. In conclusion, dietary supplementation with PJB at 2.5 g/kg improved growth performance, digestive capacity, antioxidant status, innate immune responses, and disease resistance in juvenile P. major without adverse physiological effects.