Effect of dietary Ficus carica polysaccharides on the growth performance, innate immune response and survival of crucian carp against Aeromonas hydrophila infection.

Ficus carica polysaccharides (FCPS), one of the most effective and important compo-nents in Ficus carica L., had been considered to be a beneficial immunostimulant and may be used in immunotherapy for animals and human. However, studies were little about the effect of FCPS used as immunomodulatory and the suitable dosage in fish. The present study investigated the effect of four different dietary levels of FCPS (0.1%, 0.2%, 0.4%, 0.8%) on the growth performance, innate immune responses and survival of crucian carp against Aeromonas hydrophila infection. The results showed that compared with control group, dietary FCPS had positive effects the growth performance (final weight, feed conversion ratio and survival rate) of crucian carp. FCPS induced significant higher (p < 0.05) leukocyte phagocytosis activity, serum bactericidal activity, lysozyme activity, com-plement C3, SOD activity and total protein level in the serum of crucian carp. Moreover, innate immune response of fish in FCPS groups increased first and then decreased with increasing dietary FCPS from 0.1% to 0.8%, and reached up to the peak in 0.4% dietary FCPS groups. Besides, the cumulative mortalities in FCPS groups were remarkably lower than that of control group when challenged with A. hydrophila, the relative percent survivals were 22.67%, 55.56%, 62.22% and 17.78% in 0.1% group, 0.2% group, 0.4% group and 0.8% group, respectively. These results suggested that dietary FCPS could improve the growth performance, innate immune response and disease resistance against A. hydrophila in fish, and the suitable dietary dose of FCPS was 0.4% in crucian carp.

Effects of dietary vitamin E deficiency on systematic pathological changes and oxidative stress in fish.

The aim of this study was to investigate the effects of dietary vitamin E deficiency on systematic pathological changes and oxidative stress in fish. A total of 320 healthy common carp (Cyprinus carpio) were randomized into four groups; the control group was fed a basal diet supplemented with 100 IUkg-1 of vitamin E, while the three experimental groups were fed the same basal diet with reduced vitamin E content (0, 25, or 50 IUkg-1). Findings showed that fish in the experimental groups mainly presented with sekoke disease, exophthalmia, leprnorthsis, and ascites. Histopathological and ultrastructural changes comprised nutritional myopathy with muscle fiber denaturation and necrosis, and multi-tissue organ swelling, degeneration, and necrosis. Compared with the control group, RBC count, hemoglobin content, vitamin E concentration, and superoxide dismutase activity were significantly lower in all three experimental groups. However, malondialdehyde content was considerably higher in experimental groups than in the control group. However, there was no difference in glutathione peroxidase activity among groups. In conclusion, dietary vitamin E deficiency (<100 IUkg-1) can cause severe injury and, in particular, oxidative damage in common carp. The oxidative damage might be a main influence caused by vitamin E deficiency in fish. These findings reveal the complete systematic pathological effect of vitamin E deficiency in common carp, which may be applicable to other fish and animals.

Plant polysaccharides used as immunostimulants enhance innate immune response and disease resistance against Aeromonas hydrophila infection in fish.

Plant polysaccharides (PPS) are an important medicinal plant product, and play a major role in preventing and controlling infectious microbes in aquaculture. The present study investigated the effect of three PPS; Ficus carica polysaccharides (FCPS), Radix isatidis polysaccharides (RIPS), and Schisandra chinensis polysaccharides (SCPS), used as feed additives, on innate immune responses and disease resistance against Aeromonas hydrophila in crucian carp. Results show that crucian carp fed with these PPS showed significant (p < 0.05) enhancement of their innate immune response including leukocyte phagocytosis activity, serum bactericidal activity, lysozyme activity, total protein level, complement C3, and superoxide dismutase activity compared with the control group. Their degree of influence on these immune parameters was in the order of FCPS > RIPS > SCPS, except for lysozyme activity (RIPS > FCPS > SCPS). In addition, fish cumulative mortalities in the three treatment groups were remarkably lower than in the control group (95%) when challenged with A. hydrophila, relative percent survivals were 57.9%, 47.4%, and 42.1% in FCPS, RIPS, and SCPS groups, respectively. These results suggest that FCPS, RIPS, and SCPS used as immunostimulants are capable of enhancing immune responses and disease resistance against A. hydrophila in crucian carp, and that FCPS was the most effective. The findings from this study will help accelerate research of this topic, and promote the application and development of immunostimulants, such as Chinese herbs, in aquaculture.