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Effects of dietary Lactobacillus acidophilus and tussah immunoreactive substances (TIS) on disease resistance of sea cucumber (Apostichopus japonicus) against Vibrio splendidus were investigated. Sea cucumbers were fed with a basal diet in the control group (CK group) or were supplemented with L. acidophilus (L group), TIS (T group) or both (LT group). The challenge test with V. splendidus was conducted after the feeding trial. The cumulative mortality rate in the LT group was significantly lower, while the highest mortality occurred in the control group. The LT group showed better digestive and immune parameters compared with the other treatments. Dietary L. acidophilus and TIS in combination could effectively enhance digestive function and food uptake, depress oxidative damage and improve the organismal defence capability. Regarding gut microbiota profiles, the LT group was more capable of inhibiting potentially opportunistic pathogens and regulating intestinal flora balance compared with the other groups. The administration of L. acidophilus and TIS in the diet could effectively improve disease resistance against V. splendidus of sea cucumbers by improving the immune and digestive enzyme activities and modulating intestinal microflora, signalling a potential role in the development and production of aquatic feed. [ABSTRACT FROM AUTHOR]

To investigate the effects of Lactobacillus acidophilus and tussah immunoreactive substances (TIS) supplementation alone or together on the growth performance, digestive and immune-related enzyme activities, and intestinal microbiota of the sea cucumber Apostichopus japonicus , a feeding experiment was conducted. The supplementation of L. acidophilus and TIS together produced the maximum digestive and immune activities, while the minimum values occurred in the control group. No remarkable differences in enzyme activities were observed when supplemented individually. Dietary L. acidophilus and TIS in combination might be more capable of improving digestive capacity, food utilization rate, phosphatase-responsiveness and antioxidants. Furthermore, the supplementation of L. acidophilus and TIS in combination demonstrated a greater ability to optimize the intestinal microbiota of A. japonicus by increasing the potentially beneficial bacteria involved in energy production and biosynthesis, and suppressing the opportunistic pathogens. These results collectively indicated that the combined supplementation of L. acidophilus and TIS has a synergistic effect on enhancing immunity and digestibility, and could improve the intestinal microbiota structure of A. japonicus , suggesting potential for industrial feeding applications. [Display omitted] • L. acidophilus and TIS improved the digestibility and immunity of sea cucumbers. • L. acidophilus and TIS optimized the community composition of sea cucumbers. • The positive effects were more obvious by applying L. acidophilus and TIS together. [ABSTRACT FROM AUTHOR]