Effects of dietary ß-glucans on the productive performance, blood parameters, and intestinal microbiota of angelfish (Pterophyllum scalare) juveniles.

Among the potential feed additives, ß-glucans are known to positively affect the growth performance, blood parameters, and intestinal microbiota of fish, even the ornamental species. Therefore, the present study evaluated the effects of the dietary supplementation of different Saccharomyces cerevisiae ß-glucans concentrations (0, 0.05, 0.1, and 0.2%) in juvenile angelfish (Pterophyllum scalare) over a 42-day period. Regarding growth performance, no effects were observed on most parameters. However, 0.2% ß-glucans supplementation produced higher condition factor values, indicating a better nutritional status. Furthermore, ß-glucans supplementation did not affect blood parameters. Regarding intestinal microbiota, ß-glucans supplementation increased the abundance of the potentially beneficial bacterial genus Phascolarctobacterium. The high abundance of bacteria from the phylum Bacteroidetes, which can degrade ß-glucans, may be attributed to the increased abundance of Phascolarctobacterium spp. In addition, 0.2% ß-glucans supplementation produced more operational taxonomic units and higher Sobs (observed species richness), indicating effects on the overall bacterial community structure. These results demonstrate the potential application of ß-glucans as a dietary supplement to improve the performance and modulate the intestinal microbiota of angelfish.

Development of Fish Immunity and the Role of ß-Glucan in Immune Responses.

Administration of ß-glucans through various routes, including immersion, dietary inclusion, or injection, have been found to stimulate various facets of immune responses, such as resistance to infections and resistance to environmental stress. ß-Glucans used as an immunomodulatory food supplement have been found beneficial in eliciting immunity in commercial aquaculture. Despite extensive research involving more than 3000 published studies, knowledge of the receptors involved in recognition of ß-glucans, their downstream signaling, and overall mechanisms of action is still lacking. The aim of this review is to summarize and discuss what is currently known about of the use of ß-glucans in fish.