Effects of a highly purified fucoidan from Undaria pinnatifida on growth performance and intestine health status of gibel carp Carassius auratus gibelio

A six-week feeding trial was conducted to determine the effects of different concentrations of fucoidan (1 g/kg, 10 g/kg and 30 g/kg; w/w) from Undaria pinnatifida on gibel carp (Carassius auratus gibelio). Our results demonstrated that 30 g/kg fucoidan significantly increased (p < .05) growth performance, intestinal digestive enzyme activities, acid phosphatase activity and immunoglobulin M content. Histological examinations revealed that gibel carp receiving 30 g/kg fucoidan had significant higher abundance of mucin-containing goblet cells in middle and distal intestine as compared with control treatment (p < .05). Intestinal microbiota analysis showed that 30 g/kg fucoidan supplementation significantly increased (p < .05) the abundance of Cetobacterium and Aeromonas, but lowered (p < .05) the prevalence of pathogenic bacteria Plesiomonas and a mucin-degrading bacterium Mucinivorans. Furthermore, RNA-seq and RT-qPCR analysis indicated that 30 g/kg fucoidan caused significant changes (p < .05) in the expression of genes involved in immune regulation (such as interleukin-8 and cyclooxygenase), signal transduction (such as phosphatidylinositol-4,5-bisphosphate 3-kinase and protein kinase B) and nutrition utilization (maltase-glucoamylase and muscarinic acetylcholine receptor 3). Together, the current study shows that fucoidan supplementation could elevate the activity of intestinal digestive enzymes, modulate intestinal microbial communities and potentiate a higher state of immune readiness, which might consequently improve growth performance and intestine health status of gibel carp.