Effects of Selenium Yeast Addition on the Growth, Intestinal Health, Immune Status and Body Composition of Juvenile Sea Cucumber <i>Apostichopus japonicus</i> before and after Aestivation

Abstract

This study was performed to investigate the effects of selenium yeast (Se-yeast) on the growth, intestinal health, immune status and body composition of juvenile Apostichopus japonicus before and after aestivation. Five experimental diets were formulated with increasing addition of Se-yeast (0, 0.5, 1.0, 1.5 and 2.0 mg/kg), with the diet without Se-yeast as the control. Each diet was randomly assigned to three tanks of juvenile A. japonicus (initial body weight: 2.96 ± 0.04 g). The whole experiment lasted for 135 days, which included a 45-day feeding experiment before aestivation, a 60-day aestivation phage and a 30-day feeding experiment after aestivation. The results showed that weight gain rate (WGR) was significantly increased by the increasing addition of Se-yeast before aestivation. After aestivation, WGR was markedly elevated by 1.0 mg/kg Se-yeast but was inhibited by 1.5–2.0 mg/kg Se-yeast. The evisceration rate (ER) of A. japonicus was obviously inhibited by the relatively higher addition level of Se-yeast (1.5–2.0 mg/kg) before aestivation. After aestivation, the ER was significantly inhibited by Se-yeast at an addition of 1.5 mg/kg. Before aestivation, the highest activities of all digestive enzymes were obtained by Se-yeast addition at a level equal to or above 1.0 mg/kg Se-yeast. After aestivation, the activities of most digestive enzymes were maximized by Se-yeast at the addition level of no more than 1.0 mg/kg. Before aestivation, the activities of nitric oxide synthase and alkaline phosphatase significantly increased by the increasing addition of Se-yeast. After aestivation, immune related parameters exhibited the highest or comparable values when the addition level of Se-yeast was equal to or less than 1.0 mg/kg. Notably, the selenium content in the body wall of A. japonicus increased significantly as Se-yeast addition increased in the diets. These results showed that Se-yeast at the addition level of 1.5–2.0 mg/kg before aestivation and 1.0–1.5 mg/kg after aestivation was beneficial for the promotion of growth, intestinal health and immune status of juvenile A. japonicus.

Keywords

• <i>A. japonicus</i>
• sea cucumber
• selenium yeast
• growth performance
• digestive enzymes
• evisceration rate