Taurine improves health of juvenile rice field eel (Monopterus albus) fed with oxidized fish oil: Involvement of lipid metabolism, antioxidant capacity, inflammatory response

An 8-weeks feeding experiment was performed to evaluate the potential effect of dietary taurine on the growth, liver oxidative stress and lipid metabolism, intestinal integrity and inflammatory response as well as the skin pigments of Monopterus albus fed with the oxidized fish oil diet. With that purpose, four iso-nitrogenous and iso-lipid experimental diets were formulated, including FO (2% fresh fish oil), OO (2% oxidized fish oil completely replacing the fresh fish oil in FO group) supplemented with 0%, 0.2% (OOT0.2) and 0.5% (OOT0.5) taurine. Each diet was randomly fed to triplicate groups of 50 fish (average initial weight 30.09 ± 0.06 g). The results showed that long-term feeding of OO diet did not affect the growth performance, while decreased the contents of serum immune parameters, lowered the liver antioxidative enzymes activities and induced oxidative stress, caused abnormal fat deposition in liver by interfering lipid metabolism-related genes mRNA express profile, simultaneously accompanied by hepatocyte atrophy, destroyed the intestinal mucosal barrier through dysregulation of the mRNA expression of tight junction proteins and raised the inflammatory response by elevating the pro-inflammatory cytokines mRNA abundance, and generated undesirable skin hyperpigmentation via boosting tyrosinase activity. Notably, taurine administration improved the growth performance and partially mitigated the negative impacts in M. albus subjected to the oxidized fish oil. Taken together, it was supposed that taurine exerted its anti-oxidative and anti-inflammatory properties to confer protection against oxidized fish oil. These findings would provide a theoretical basis for the application of taurine in aquatic feed.