Gum–Gelatin Nanocapsules of Pomegranate Phenolic Extract Promote Redox Homeostasis, Metabolic Health, Immunity, Gut Microbiota, and Growth in Newly Weaned Rabbits

Pomegranate peel, a rich agro-industrial by-product, contains abundant phenolic compounds with strong antioxidant and antimicrobial properties. However, the low stability and bioavailability of these compounds limit their efficacy in animal nutrition. This study investigated the effects of pomegranate peel phenolic extract (PE), either in raw form (PE300) or nano-encapsulated using gum-gelatin nano-capsules (NPE300), on health and growth parameters in newly weaned rabbits. Fifty-four male rabbits (40 days old) were assigned to three treatment groups: PE0 (control), PE300 (300 mg PE/L drinking water), and NPE300 (300 mg nano-encapsulated PE/L drinking water). Over six weeks, growth performance, hematological and immunological profiles, antioxidant status, microbial populations, and carcass traits were evaluated. NPE300 treatment demonstrated superior antimicrobial activity <i>in vitro</i>, with larger inhibition zones against all tested pathogens compared to PE300. <i>In vivo</i>, NPE300 significantly improved body weight gain (945.8 g) and feed efficiency, while also enhancing immune function, evidenced by higher white and red blood cell counts, phagocytic activity, and increased plasma IgG and IgM levels. Antioxidant markers showed that NPE300 significantly reduced malondialdehyde levels and tended to improve total antioxidant capacity. Furthermore, intestinal <i>Clostridia</i> counts were reduced, and beneficial microflora significantly increased in the NPE300 group. Carcass weight with edible parts, fur weight, kidney weight, and cecum length were also elevated under NPE300 treatment. In conclusion, nanoencapsulation of PE using gum-gelatin carriers enhanced its bio-efficacy, supporting better redox balance, immunity, gut health, and growth performance in rabbits. These findings support the application of nano-encapsulated PE as a promising natural growth promoter in rabbit production.