Correlation of duration of β-1,3/1,6-glucan administration with the effectiveness of immune stimulation in juvenile vimba bream

Introduction: The purpose of this study was to determine how the duration of administration of β-glucans derived from the yeast Material and Methods: The effects of two treatments were compared at three endpoints using a 2 × 3 factorial design, all groups in triplicate aquaria (n = 3). Kept in controlled recirculating aquaculture system conditions, three experimental groups were fed for two, four or eight weeks a commercial starter feed, and three other groups received the same feed supplemented with a commercial formulation of β-glucan polysaccharides from the cell wall of Results: Two-week administration of β-glucan in the diet resulted in significantly higher pinocytosis, respiratory burst activity and potential killing activity of head-kidney phagocytes in supplemented fish compared to phagocytic activities in fish not receiving β-glucan. However, in the groups receiving β-glucan for four and eight weeks, this activity was significantly lower than in the respective control groups. After eight weeks, T-lymphocyte activity was also lower. Conclusion: Under controlled recirculating aquaculture system conditions favourable for fish growth, the most beneficial effect of dietary β-glucan supplementation on vimba bream immune cells appears after two weeks. Extension of this period to four or eight weeks loses beneficial effects, and even significantly decreases some immune parameters. This finding is critical for animal nutrition, where glucans or their sources are increasingly used as permanent components of feed.