Oxidized fish oil in the diet negatively affect rearing performance, health, and tissue fatty acid composition of juvenile spotted rose snapper Lutjanus guttatus (Steindachner, 1869)

Lipids are essential in feeds for rearing marine fish. Inadequate handling and storage of feeds can cause lipid oxidation, increasing toxic compounds while decreasing the nutrition quality of feeds and negatively affecting both the physiology and rearing performance of fish. Here, the effect of increasing oxidized lipids intake was assessed on rearing performance and health of juvenile L. guttatus. Experimental feeds (EF) were manufactured with different levels of total peroxides (PV, 26-107 meqO(2) x kg(-1)) and anisidine value (AV, 74-154). A total of 270 fish (18 fish by tank, three replicates by treatment) with an initial average weight of 6.5 +/- 1 g were reared in 3 m(3) tanks for 45 days. Survival and growth rate decreased with increasing PV and AV, particularly in fish fed with higher values of oxidized lipids. Viscerosomatic index was positively correlated with increase of oxidized lipids in EF, probably caused by increasing food retention into the gut. Glucose in plasma was inversely correlated with PV and AV in EF and together with the damage observed (i.e., inflammatory nodules, necrosis, and higher hepatosomatic index) suggests a decrease of liver metabolism. The increases of PV and AV on feeds were positively correlated with levels of triacylglycerides and total cholesterol in plasma, indicating an alteration in lipid metabolism. The total protein content in plasma and hematocrit was not different among treatments; in contrast, hemoglobin content decreased compared with control, suggesting an increase in the fragility of blood cells and oxygen transport capacity. Highly unsaturated fatty acid (HUFA) composition in the brain and liver was not different between treatments, but PV and AV were inversely correlated with docosahexaenoic acid (DHA) levels in neutral lipids and eicosapentaenoic acid (EPA) and arachidonic acid (ARA) levels in polar lipids in liver tissue, suggesting a specific demand to counteract cell damage caused by the accumulation of oxidized lipids. The content of HUFA in total lipids from muscle suggests this is an important storage tissue, whereas EPA level decreased with oxidized lipids in the diet. The results showed that increasing oxidized lipids on the diet compromise the health condition and rearing performance of juvenile rose snapper L. guttatus.

Automated summary

Lipid oxidation in feeds can negatively affect the health and rearing performance of juvenile marine fish. Increasing intake of oxidized lipids decreases survival, growth rate, and liver metabolism, while also altering lipid metabolism and blood cell fragility. These results indicate the importance of proper handling and storage of feeds to maintain their nutrition quality.