Preliminary evaluation of dietary pomegranate (Punica granatum) peel powder effects on systemic immunity, antioxidant status, and reproductive performance in goldfish (Carassius auratus)

Abstract Background Pomegranate peel powder (PPP) is a polyphenol-rich by-product with antioxidant and immunomodulatory properties. Although PPP has been shown to improve growth in goldfish ( Carassius auratus ), its effects on immunity, antioxidant status, and reproductive performance have not been comprehensively evaluated. Objective This preliminary study aimed to investigate the effects of dietary PPP supplementation on haematological parameters, systemic and mucosal immune responses, serum biochemical indices, oxidative stress biomarkers, and reproductive performance in goldfish. Methods A total of 240 goldfish (initial weight: 17.4 ± 1.7 g) were randomly distributed among 12 tanks (3 replicates per treatment) and fed diets containing 0%, 1%, 2%, or 4% PPP for 70 days. Chemical analysis of PPP revealed high phenolic content (187 mg GAE/g), punicalagin α (24.8 mg/100 g), and ellagic acid (6.7 mg/100 g). Standard methods were used to assess immune, biochemical, oxidative, and reproductive parameters. Results The strongest effects were observed at the 4% PPP inclusion level. Fish fed 4% PPP exhibited significantly higher white blood cell counts, serum lysozyme activity, and total immunoglobulin levels ( P < 0.05). Serum total protein and albumin concentrations increased, while AST and ALP activities decreased in the 4% PPP group ( P < 0.05). PPP supplementation was associated with a significant reduction in malondialdehyde levels and elevated superoxide dismutase, catalase, and reduced glutathione, suggesting enhanced antioxidant defence. In contrast, mucosal immune parameters remained unaffected ( P > 0.05). Following HCG-induced maturation, fish receiving 4% PPP showed improved sperm concentration, fertilisation rate, and gonadosomatic index ( P < 0.05). Conclusion Dietary PPP at 4% was associated with enhanced systemic immunity, improved antioxidant status, favourable serum biochemical changes, and better reproductive outcomes in goldfish. However, because the diets were not isonitrogenous or isoenergetic, these findings are preliminary and hypothesis-generating. Controlled trials with standardised diets are needed to confirm the functional efficacy of PPP.