Effect of probiotic feed supplementation on skin ulceration syndrome in <em>Apostichopus japonicus</em>

Abstract

Skin ulceration syndrome is among the most harmful diseases in sea cucumber (<em>Apostichopus japonicus</em>). The annual loss due to this disease is more than 1 billion dollars, which seriously affected the healthy and sustainable development of <em>A. japonicus</em>. In this paper, animals were divided into 4 experimental groups: a control group given basic feed, experimental groups with 1% <em>Lactobacillus</em>, 1% <em>Bacillus</em>, 1% mixture with 0.5% <em>Lactobacillus</em> and 0.5% <em>Bacillus</em> added to the basic feed. After feeding for 60 days, the samples were taken to analyze the growth performance, digestive enzyme activity, and immune indexes of <em>A. japonicus</em>. Furthermore, the resistance to the skin ulceration syndrome of <em>A. japonicus</em> was analyzed. The results showed that the probiotics promoted the growth performance of <em>A. japonicus</em>, the weight gain rate of the control group was 120.08±12.07%, the weight gain rate of the <em>Lactobacillus</em> group was 152.11±10.06%, the weight gain rate of the <em>Bacillus</em> group was 148.03±9.88%, and the weight gain rate of the mixed bacteria group was as high as 210.11±19.41%. The digestive enzyme activities in the intestinal tract of <em>A. japonicus</em> increased significantly in the probiotic-added groups, and the mixed bacteria were more effective in enhancing the digestive enzyme activities than single <em>Bacillus</em> and <em>Lactobacillus</em>. In addition, the probiotics could significantly increase the phagocytosis rate of the body cavity cells of <em>A. japonicus</em>. The phagocytic rate of <em>Lactobacillus</em> and <em>Bacillus</em> subtilis was comparable; the mixed probiotics were significantly higher than those of single probiotics, and this phagocytic rate gradually increased over time. After <em>Vibrio splendidus</em> and <em>Pseudoalteromonas</em> infection, the mortality rate of <em>A. japonicus</em> in the probiotic-added group was reduced, which indicated that probiotics could improve the immunity of <em>A. japonicus</em>, and the ability to resist the infection of <em>Vibrio splendidus</em> and <em>Pseudoalteromonas</em> was enhanced. <em>Bacillus</em> exhibits superior antimicrobial ability compared to <em>Lactobacillus,</em> and the mixed strain displays the most effective antimicrobial properties. This study provided a scientific basis for effectively preventing and controlling skin ulceration syndrome in the aquaculture of <em>A. japonicus</em>.