Effects of dietary probiotic yeast on growth parameters in juvenile sea cucumber, Apostichopus japonicus

An 8-week feeding trial was conducted to evaluate the effects of oral administration of the probiotic yeast Rhodotorula sp. H26 in combination with Metschnikowia sp. C14 on the growth, digestive enzyme activity, body composition, immunity, and intestinal microbiota in the juvenile sea cucumber, Apostichopus japonicus. Sea cucumbers were distributed into four groups and received one of the following diets: BD) basal diet; H) BD + H26; C) BD + C14; or HC) BD + H26 + C14. After 4-8 weeks of feeding, sea cucumbers that were fed with the HC diet showed a significant increase in specific growth rate, pepsin, trypsin, amylase, and lipase activities compared with the BD diet group and/or single probiotic yeast s1 s0. H26 or C14) groups (P < .05); the body wall crude protein and carbohydrate/ash contents in sea cucumbers fed the HC diet were significantly higher/lower than those in the BD and/or single probiotic yeast (H26 or C14) groups (P < .05). After 8 weeks of feeding, a significantly higher content of arachidonic acid (20:4n-6), and lower contents of oleic acid (18:1) and eicosadienoic acid (20:2n-6) plus eicosatrienoic acid (20:3n-9) were detected in the body wall of sea cucumbers fed the HC diet compared to those fed the BD diet (P < .05). Feeding the mixture for 4 and/or 8 weeks significantly improved phagocytic activity and respiratory burst in coelomocytes (P < .05). In addition, there was an observed enhancement in lysozyme activity and phenoloxidase activity in coelomic fluid supernatant and in coelomocyte lysate supernatant compared with the BD and single probiotic yeast (H26 and/or C14) groups (P < .05). After feeding for 4 and/or 8 weeks, sea cucumbers fed the HC diet showed a significant increase in the numbers of total bacteria, and a decrease in the numbers of vibrio bacteria in the intestine compared with the BD group (P < .05). After 8 weeks of feeding, gel electrophoresis revealed that the mixture of H26 and C14 did not significantly affect the composition of intestinal microbiota. These data suggest that a mixture of H26 and C14 supplementation can improve the growth, enhance digestive enzyme activity, add nutritional value and stimulate the innate immune system of sea cucumber juveniles.