Effect of different selenium source on growth performances, glutathione peroxidase activities, muscle composition and selenium concentration of allogynogenetic crucian carp (Carassius auratus gibelio)

A feeding experiment was carried out to compare the effects of supplementing a fish meal-based diet with selenium as sodium selenite or selenomethionine on allogynogenetic crucian carp (Carassius auratus gibelio). Three groups with three replicates of crucian carps (mean weight 14.5 ± 0.49 g) were given a basal diet either unsupplemented (control) or supplemented with 0.5 mg Se kg−1 as sodium selenite (trial 1) or selenomethionine (trial 2) respectively, for 30 days. There was significant difference (P<0.05) in relative gain rate (RGR) of trials 1–2 compared with the control. However, there were no significant differences (P>0.05) in final weight and RGR between the trials 1 and 2. Survival rate and feed conversion ratio (FCR) were not affected by the dietary treatments. Fish fed the basal diet showed lower (P<0.05) selenium content in muscle (5.87 ± 1.12 μg g−1) compared to fish fed selenium supplements (trials 1–2, 11.0 ± 1.57 μg g−1 and 14.2 ± 1.05 μg g−1, respectively). Furthermore, trial 2 showed the highest value (P<0.05) among these treatments. However, there was no significant difference (P>0.05) in muscles composition of carps between these treatments. Glutathione peroxidase (GSH-Px) activities in crucian carps plasma and liver of all selenium treatment groups (trials 1–2) were significantly different (P<0.05) from that of the control (Fig. 1). The GSH-Px activity in plasma was remarkably higher (P<0.05) in trial 2 compared with trial 1 and the control. However, there was no difference (P>0.05) in hepatic glutathione peroxidase between trials 2 and 1 although the average value of GSH-Px activity in trial 2 presented the trend of increase.