Dietary Effect of Probiotic and Prebiotic on Some Mucus Indices of Silver Carp (Hypophthalmichthys molitrix) Exposed to Silver Nanoparticles

Dietary Effects of Probiotic Lactobacillus casei on Some Immunity Indices of Common Carp (Cyprinus carpio) Exposed to Cadmium

The present study investigated the effect of feeding common carp with Lactobacillus probiotic supplement on growth, blood indices, and immunity of serum and mucus exposed to cadmium. A total of 250 common carp with an average weight of 15 ± 0.62 were divided into three groups: fish without probiotics, and fish with two levels of probiotic. At the end of a 42-day feeding period, 50% of the lethal concentrations of cadmium were exposed for 14 days and blood and immune indices of serum and mucus were measured. The results showed that growth indices, blood indices, and serum and mucus immunity were significantly different from the control group (P < 0.05). Finally, this study showed probiotics could improve the decreasing effect of cadmium in BWI and PBWI indices and the additive effect of cadmium in FCR and ALT. Probiotic was also able to completely improve the decreasing effect of cadmium on lymphocyte indices and the additive effect of cadmium on ALP and AST and monocyte.

Chronic Toxic Effects of Waterborne Mercury on Silver Carp (Hypophthalmichthys molitrix) Larvae

Mercury (Hg) is a kind of heavy metal pollutant widely existing in the aquatic environment, and it is also recognized to have a highly toxic effect on fish. In this study, silver carp (Hypophthalmichthys molitrix) larvae were exposed to 0 (control), 1, 5, and 10 μg/L Hg2+ for 2 weeks. Antioxidant ability, neurotoxicity, and thyroid hormones (THs) content were evaluated. In comparison with the control, the superoxide dismutase (SOD) activity and the glutathione (GSH) activity were lower in silver carp exposed to 10 μg/L Hg2+. The lowest catalase (CAT) activity was found in the 10 μg/L Hg2+, while malondialdehyde (MDA) content was not significantly different among all groups. Compared with the control, monoamine oxidase (MAO) activity and nitric oxide (NO) content were significantly higher in the 10 μg/L Hg2+, while acetylcholinesterase (AChE) activity significantly decreased. Compared with the control, triiodothyronine (T3) content was significantly higher in the 1 μg/L Hg2+ and significantly lower in the 10 μg/L Hg2+; the 1 μg/L and 5 μg/L Hg2+ groups had significantly higher thyroxine (T4) content than the other groups. In the 1 μg/L Hg2+, the integrated biomarker response (IBR) index value was the highest. In summary, exposure to Hg could decrease the antioxidant ability, cause changes in neurotoxic parameters, and induce disorders of the thyroid hormone system in silver carp larvae. The results of this study may contribute to the understanding of the adverse effects of chronic mercury poisoning on fish.