Dietary inosine and uracil efficacy on immune and growth genes expression, physiological performance and intestinal topography of juvenile sea bream (Sparus aurata)

The effect of inosine (I) and uracil (U) supplementation on growth; carcass biochemical composition; immune and growth promoter genes expression; antioxidant and oxidative stress markers; and intestinal morphology of sea bream (Sparus aurata) fingerlings was studied. Seven experimental diets were used: control basal (Ctrl) diet, inosine (I) supplemented at 2.5 (I1), 5 (I2) and 10 (I3) g/kg diet, and uracil (U) supplemented at similar inclusion levels as inosine. Results showed that diets I3, I2, and U1 had positive effects on fish growth and feed utilization. The I3 group had the highest protein and the lowest lipid contents while U supplementation had no significant effect on fish protein content. For insulin-like growth factors, ilgf-1 and ilgf-2, gene expression was significantly higher in I3 fed fish. il-1 beta expression in head kidney increased in all studied groups non-significantly except I1, while tnf-alpha and Selel gene expression was greater in I3. Intestinal, gill and hepatic superoxide dismutase and catalase activities were higher (p < 0.05) in I-supplemented groups in an increasing concentration-dependent manner compared to other groups. Hepatic malondialdehyde (MDA) decreased in I2 fed fish, while intestinal and gill MDA was decreased in the I3 treatment. Sea bream-fed U2 recorded the lowest MDA activity relative to other U-supplemented groups. Inosine at all supplementation levels significantly increased villi length and width, epithelial thickness and goblet cell number. Supplementation of I and U improved fish tolerance to low oxygen and low salinity exposure compared to Ctrl. In conclusion, 5-10 g/kg diet of (I) or 2.5 g/kg diet (U) promotes fish growth, intestine health, immune response and resistance to stress exposure and reduces oxidative stress condition.

Automated summary

Supplementation of inosine (I) and uracil (U) in sea bream fingerlings' diet enhances growth, improves intestinal health, boosts immune response, increases resistance to stress exposure, and reduces oxidative stress levels.