Partial replacement of dietary fish oil by beef tallow does not impair antioxidant capacity and innate immunity of red swamp crayfish, Procambarus clarkii

Abstract

Beef tallow (BT) has attracted research interests of fish oil (FO) sparing in aquafeed, but total replacement of dietary FO by BT might damage aquatic animal health as a controversial issue for years. This study aimed to investigate the effects of BT partially or completely replacing FO on the health of red swamp crayfish (Procambarus clarkii), especially antioxidant capacity and immune response. Three experimental diets containing FO, BT and a blend of FO and BT (FB, 1:1) as lipid sources, respectively, were formulated to feed crayfish for 8 weeks. The results showed crayfish exhibited no significant differences (p > 0.05) in growth and body proximate composition regardless of dietary lipids. Crayfish fed a BT diet were observed higher contents of haemolymph triglyceride and free fatty acid (FFA) compared with crayfish fed FO (p < 0.05), while FB diet tended to reverse this effect. For hepatopancreas antioxidants, crayfish in the FB group showed higher levels of catalase and glutathione and lower malondialdehyde content than those in the FO group (p < 0.05). Furthermore, BT diet feeding decreased the contents of haemolymph acid phosphatase, lysozyme and total protein compared with FO diet, but FB diet tended to improve these immunological parameters. FB inclusion reversed the BT-induced suppression of nuclear factor kappa beta mRNA expression and enhancement of mitochondrial manganese mRNA expression versus BT, implying ameliorative immunity function. Taken together, total replacement of dietary FO by BT might be detrimental to the health of crayfish, while partial substitution of dietary FO with BT neither suppresses growth nor impairs antioxidant capacity and innate immunity of crayfish.