Caroline Azzolin Bressan

Mugil liza juveniles (6.69 ± 0.06 g) were subjected to dietary citral (0-control, 0.5, 1.0 and 2.0 mL per kg feed) for 45 days, and its possible effects on zootechnical and metabolic parameters, digestive enzymes, innate immunity, oxidative status and liver damage were evaluated. At the end of the experiment, fish fed 2.0 mL citral per kg feed showed a greater weight gain and protein retention efficiency, as well as enhanced activities of pepsin (stomach) and amylase (intestine) compared with control fish. Citral supplementation decreased liver lipoperoxidation and increased the activities of glutathione peroxidase, glutathione-S-transferase and superoxide dismutase in the gills, liver and brain. The highest level of citral inclusion augmented non-protein thiol content in the brain and gills. Myeloperoxidase activity was lower in fish offered 1.0 and 2.0 mL citral per kg feed. Dietary citral did not influence the plasma levels of aspartate aminotransferase and alanine aminotransferase or the hepatic histology. As it improved growth, the activity of digestive enzymes and general health, dietary citral may be recommended for M. liza at 2.0 mL per kg feed.

R-(+)-limonene is a monoterpene from plants of the genus Citrus with diverse biological properties. This research evaluated the effects of dietary supplementation with R-(+)-limonene on growth, metabolic parameters in plasma and liver, and the antioxidant and stress responses in silver catfish, Rhamdia quelen, challenged or not with Aeromonas hydrophila. Fish were fed for 67 days with different doses of R-(+)-limonene in the diet (control 0.0, L0.5, L1.0, and L2.0 mL/kg of diet). On the 60th day, a challenge with A. hydrophila was performed. R-(+)-limonene in the diet potentiated the productive performance of the fish. The metabolic and antioxidant responses indicate that R-(+)-limonene did not harm the health of the animals and made them more resistant to the bacterial challenge. Histological findings showed the hepatoprotective effect of dietary R-(+)-limonene against A. hydrophila. Igf1 mRNA levels were upregulated in the liver of fish fed with an L2.0 diet but downregulated with bacterial challenge. The expression levels of crh mRNA were higher in the brains of fish fed with the L2.0 diet. However, the L2.0 diet downregulated crh and hspa12a mRNA expression in the brains of infected fish. In conclusion, the results indicated that R-(+)-limonene can be considered a good dietary supplement for silver catfish.