Construction of healthy liver of largemouth bass in short-term by steroidal saponins before heat season coming

Abstract

Saponins has been confirmed to alleviate tissues damage in mice exposed to high temperatures. Focusing on the industrial development of largemouth bass (Micropterus salmoides), this study exihbited the effects of steroidal saponins (SS) on the growth performance and the liver health of largemouth bass under the high-temperature stress. Two experiments were carried out, the first trial was designed to evaluate the growth performance of fish fed the experimental diets containing SS 0 and 0.1% (SS0 and SS0.1) for one month. And then the second trial was put into effect to evaluate these fish under the high-temperature stress for one week, and the groups were name as SS0, HSS0, SS0.1 and HSS0.1, respectively. In the first feeding trial, the higher feeding rate was found in SS0.1 group (P < 0.05), no significant difference was observed between the groups SS0 and SS0.1 in survival rate, weight gain rate, special growth rate and feed coefficient rate, respectively. After one week of high-temperature stress, specific growth rate, weight gain rate of fish were higher in the SS0 and SS0.1 groups than in the HSS0 and HSS0.1 groups (P < 0.05). In terms of feeding rate, the SS0.1 and HSS0.1 groups were significantly higher than the other two groups (P < 0.05). Hepatic il-8 gene expression was down-regulated in largemouth bass fed with 0.1% SS regardless of temperature. Under high temperature stress, genes expression of caspase-3, caspase-8, caspase-9, tnf-α, il-8 and hsp70 were significantly down-regulated in the liver of largemouth bass reard in HSS0.1 group. The activities of antioxidant enzymes catalase, total superoxide dismutase and glutathione peroxidase in the liver were significantly increased and serum enzyme activities of aspartate aminotransferase and alanine aminotransferase were significantly decreased in HSS0.1 group (P < 0.05). Compare to HSS0 group, hepatic vacuolization areas of fish in HSS0.1 group were improved (P < 0.05). Therefore, the results of the study supported that the 0.1% SS used in the diet feeding largemouth bass for one month could strengthen the body health, and the liver showed the more healthy when the fish sufferred the high-temperture stress compare to the fish fed diet free SS.