LAUSR

Abstract A study was conducted to characterize the effects of dietary oxidized fish oil on the intestinal enzyme activities, morphology, microbiome composition of genetically improved farmed tilapia (Oreochromis niloticus) and to determine the role of ferulic acid on the intestinal oxidative damage induced by the oxidized fish oil and intestinal microbiota. The tilapia (13.73 ± 0.31 g) were fed four experimental diets containing untreated (peroxide value, POV: 2.2 meq kg−1) and highly oxidized (POV: 120.6 meq kg−1) fish oil either with or without ferulic acid (0 or 400 mg kg-1) supplementation for 12 weeks. From the results, the oxidized fish oil treatments increased antioxidant enzyme activities and MDA values in serum and intestine, but decreased the activities of digestive enzymes. In the oxidized fish oil-receiving groups, intestinal villus height and villus width were significantly reduced, and the muscular thickness was significantly increased in tilapia. Besides, the oxidized fish oil might cause the dysbiosis of intestinal microbiota. Meanwhile, the addition of ferulic acid partially counteracted the free radical-induced damage and improved the intestinal health of tilapia. In conclusion, the oxidized fish oil may induce oxidative stress, destroy the intestinal morphology, lower digestive capacity as well as disturb the stability of microbial community, whereas ferulic acid supplementation partially offset the negative effects of the oxidized fish oil on tilapia.