Dietary beta-glucan modulate haematological parameters, cytokines and gene expression in TLR and ERK pathways of rainbow trout (Oncorhynchus mykiss) during infection by Aeromonas salmonicida

To explore the role of beta-glucan (0, 0.05%, 0.1% and 0.2%) in resisting bacteria, rainbow trout (Oncorhynchus mykiss) was challenged with Aeromonas salmonicida after 42-day beta-glucan administration, and then sampled at 0, 2, 4 and 6 days post infection (dpi). The data showed that 0.2% beta-glucan reduced the accumulated mortality rates compared with the ICG (infected control group) (p ). The white blood cells, red blood cells and haemoglobin were higher in the 0.2% beta-glucan group (BG) than the ICG (p ). 0.1% and 0.2% beta-glucan elevated serum total antioxidative capability and glutathione activity but alleviated the increase of serum alkaline phosphatase activity and glucose concentration (p < .05) during infection. Serum TNF-alpha, IL-1 beta, IL-8 and IgM in three BGs elevated remarkably on 6 dpi compared with the ICG (p ). Expression of tnf, il1b and cxcl8 of the head kidney in the 0.1% and 0.2% BGs was higher than the ICG on 4 dpi while ighm expression in the 0.2% BG was higher than in the ICG on 2 and 6 dpi (p ). 0.1% and 0.2% beta-glucan increased the expression of tlr5m, tlr5s, tmek and myd88 in the spleen after infection (p < .05). Similarly, 0.2% beta-glucan up-regulated the expression of tmek, myd88, oncmyk-dab and c3 in head kidney (p < .05). Overall, 0.2% dietary beta-glucan effectively decreased accumulated mortality rate by modulating the biochemistry process, cytokines, and activating TLR and ERK signalling pathways during A. salmonicida infection.