An evaluation on the selenium yeast supplementation in the practical diets of early juvenile sea cucumber (Apostichopus japonicus): Growth performance, digestive enzyme activities, immune and antioxidant capacity, and body composition

A 45-day feeding trial was carried out to investigate the effects of dietary selenium yeast (Se-yeast) on the survival, growth performance, activities of digestive enzymes and antioxidant enzymes, and body composition of early juvenile Apostichopus japonicus. Five isoprotic (15.6%) and isolipic (1.5%) feeds with graded levels of Se-yeast (0, 0.5, 1.0, 1.5 and 2.0 mg/kg) were formulated and randomly allocated to the early juvenile sea cucumbers (initial weight: 0.11 +/- 0.01 g). The results showed that the weight gain rate (WGR) and relative visceral weight ratio (RVW) significantly increased as the Se-yeast supplementation increased from 0 to 1.0 mg/kg, and then reached a plateau with further increase in Se-yeast, while survival rate (SR) increased as the supplementation level of Se-yeast increased, and the lipase and amylase activities first significantly increased as the Se-yeast increased from 0 to 1.0 mg/kg, and then significantly decreased with the continuous supplementation of Se-yeast. The antioxidant capacity and nonspecific immunity were significantly elevated by the moderate level (0.5 and 1.0 mg/kg) of Se-yeast. Besides, the activities of immune-related enzymes and transcription of antioxidation-related genes were significantly elevated by the supplementation of Se-yeast. However, malonaldehyde contents were significantly reduced in the treatments with 0.5 and 1.0 mg/kg Se-yeast. The selenium content in the body wall of the sea cucumber showed a markedly increasing trend with increasing Se-yeast supplementation levels. Results above indicated that a moderate level (0.5-1.0 mg/kg) of Se-yeast enhanced the growth performance, digestive enzyme activities, antioxidant capacity and nonspecific immunity of early juvenile A. japonicus.