Search

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.

This study evaluates whether humic acid (HA; Aldrich) protects the silver catfish, Rhamdia quelen (Quoy & Gaimard, 1824), against exposure to acidic pH. Survival, levels of Na+, Cl- and K+ plasma, hematocrit, hemoglobin and erythrocyte morphometry were measured. Fish were exposed to 0, 10, 25 and 50 mg L 1 HA at four pH levels: 3.8, 4.0, 4.2 and 7.0 up to 96 hours. None of the fish exposed to pH 3.8 survived for 96 hours into the experiment, and survival of fish subjected to pH 4.0 decreased when HA concentration increased. Plasma Na+ levels decreased when pH was acidic, with no influence of HA, while Cl- levels declined at low pH with increased HA concentration. The levels of K+ at pH 4.0 and 4.2 increased without HA. Hematocrit and hemoglobin augmented under the effect of HA. At pH 4.0 and 4.2, erythrocytes of fish not exposed to HA were smaller, an effect that was partially offset by the presence of HA, since the values at pH 7.0 were higher. Although HA showed some positive effects changes in hematological and plasma K+ª in silver catfish caused by exposure to acidic pH, the overall findings suggest that HA does not protect this species against acidic pH because it increased mortality and Cl- loss at pH 4.0.