Impacts of different vitamin C delivery systems (liposomal and nano-liposomal) on growth, immunity, antioxidant defense, gut health, and digestive function in grey mullet (Liza ramada)

This study investigated the effects of different forms of dietary vitamin C on growth performance, immune responses, antioxidant defense, and physiological health of grey mullet (Liza ramada, mean initial weight 40.32 ± 0.15 g, n = 3) over a 60-day feeding trial. Five experimental diets were formulated: a control diet devoid of vitamin C (D1) and diets supplemented with 200 mg/kg of crystalline vitamin C (L-ascorbyl-2-monophosphate, L-AMP; D2), liposomal vitamin C (D3), nano-liposomal vitamin C (D4), or a 1:1 mixture of liposomal and nano-liposomal vitamin C (D5). Fish fed D4 exhibited the highest growth performance, with significantly (P < 0.05) greater final body weight, specific growth rate, and better feed conversion ratio compared to other groups. Digestive enzyme activities were markedly enhanced in all vitamin C-treated groups, with D4 showing the highest amylase, lipase, and protease activities. The abundance of pathogenic bacteria decreased while acid-fermentative bacteria increased in the intestinal microbiota of vitamin C-supplemented groups, particularly in D4. Blood biochemical analysis revealed elevated total protein and globulin levels, reduced glucose and cortisol concentrations, and improved lipid metabolism in D3, D4, and D5. Immune parameters, including lysozyme activity and respiratory burst (NBT), were significantly higher in D4 and D5 (P < 0.05). Hepatic antioxidant enzyme activities increased, while malondialdehyde levels decreased in D4 and D5. These findings demonstrate that nano-liposomal vitamin C and its mixture with liposomal vitamin C confer significant benefits to growth, immune function, antioxidant defenses, and overall physiological health, highlighting their potential as effective dietary supplements in aquaculture.