Effects of Dietary Vegetable Oil Mixtures including Soybean Oil on Intestinal Oxidative Stress in Gilthead Sea Bream (Sparus aurata)

SIMPLE SUMMARY: Vegetable oil inclusion in fish diets is a common practice, but their effects in the oxidative status at intestinal level, which would affect animal health and welfare, are poorly understood. In the present study, we compared the effects of different dietary treatments containing soybean oil alone or in combination with other vegetable oils in sea bream. Overall, the results revealed that the blend of soybean and linseed oils negatively affects intestinal integrity as it triggered high oxidative stress that could not be counteracted by the high levels of antioxidant enzymes. However, the addition of palm oil to the previous mixture of vegetable oils makes it possible to maintain low oxidative stress, preserving the intestinal health of the animal. In conclusion, this study demonstrates the importance that the mixture of vegetable oils in a diet can have on the intestinal health of sea bream. ABSTRACT: Fish oil is commonly replaced by vegetable oils in sea bream diets, but little is known about their effects on intestinal health regarding oxidative stress biomarkers. The negative effects of lipid peroxidation on digestive mucosa could have consequences in animal nutrition and welfare. In this study, five isonitrogenous (46%) and isolipidic (22%) diets with 75% of vegetable oils inclusion were evaluated: soybean oil (S) alone or different mixtures containing soybean oil with linseed (SL), linseed and rapeseed (SLR), linseed and palm (SLP), and linseed, rapeseed, and palm (SLRP). Gilthead sea bream juveniles were fed twice a day for 18 weeks. Pyloric caeca and proximal intestine samples were collected 24 h post feeding for lipid peroxidation (LPO), antioxidant enzyme activities (SOD, CAT, GPx, GST, and GR) and gene expression analyses. Pyloric caeca presented larger unhealthy changes in oxidative status than proximal intestine. Although SL-fed fish showed the highest antioxidant activities, they were unable to cope with LPO that in pyloric caeca was 31.4 times higher than in the other groups. Instead, SLP fish presented the best oxidative status, with low LPO levels, antioxidant enzyme activities, and gene expression. In summary, between the vegetable oils dietary mixtures tested, SPL would maintain better intestinal health.