Abstract:This study investigated the effects of different selenium sources (sodium selenite and yeast selenium) and selenium levels on growth performance, tissue selenium content, antioxidant capacity, and serum biochemical indices of Carassius auratus var. Pengze. A 2 × 3 factorial design was used for the feeding trial: Selenium source (sodium selenite and yeast selenium), selenium supplementation level (0, 0.5, and 5 mg/kg), and five diets were prepared. The control group (CON), sodium selenite group (LS and HS), and yeast selenium group (LY and HY) were established. A total of 240 C. auratus var. Pengze with an initial body weight of (210.28±1.06) g were randomly divided into five groups, with three replicates and 16 fish in each replicate. The experimental diets were fed, and the experimental period was 56 days. The results showed no significant differences in survival rate, weight gain rate, specific growth rate, and feed conversion ratio among all groups (P＞0.05). The highest muscle selenium content was observed in the high selenium yeast group, followed by the high sodium selenite group; this value was significantly higher than that of the control group (P＜0.05), and selenium sources and selenium levels had a significant interaction on muscle selenium content (P＜0.05). For liver selenium content, the highest levels were found in the high sodium selenite group, followed by the high selenium yeast group; these levels were significantly higher than those observed in the control and low selenium groups (P＜0.05). In addition, serum catalase activity was significantly increased in the high selenium yeast group compared to the control group (P＜0.05). The serum glutathione peroxidase activity in the low sodium selenite and the selenium yeast groups was significantly higher than that of the control group (P＜0.05). Furthermore, selenium sources and levels showed significant interactions that affected serum glutathione peroxidase and catalase activities (P＜0.05). In addition, serum lysozyme activity and blood glucose levels were significantly increased in the high selenium yeast group compared to the other groups (P＜0.05). Blood glucose levels in the high selenium group were also significantly higher than those in the control group (P＜0.05), with significant interactions between selenium sources and levels affecting low-density lipoprotein levels (P＜0.05). Intestinal amylase activity in the high selenium group was notably higher than that in the control and low selenium groups (P＜0.05). Moreover, trypsin activity in the selenium yeast and high sodium selenite groups was significantly increased relative to that of the control group (P＜0.05), with significant interactions between selenium sources and levels affecting trypsin activity (P＜0.05). In conclusion, utilizing high levels of selenium yeast increases tissue selenium deposition, and the administration of two levels of selenium yeast improves antioxidant capacity and intestinal enzyme activity in C. auratus var. Pengze. Similarly, using high levels of sodium selenite increases tissue selenium deposition and intestinal enzyme activity within this species, whereas employing low sodium selenite levels improves antioxidant capacity in C. auratus var. Pengze.
