Chitinolytic activity, nutrient uptake and intestinal barrier functions were investigated in gut tissues of Arctic charr (Salvelinus alpinus) fed iso-nitrogenous diets based on fish meal, with or without inclusion of zygomycetes (Rhizopus oryzae). We found that gut tissue of Arctic charr had significant chitinase activity, of both endo- and exo-chitinase iso-forms. Moreover, the distribution pattern along the GI tract of Arctic charr differed between endo-chitinase and exo-chitinase. The endo-chitinase activity in stomach tissue and in the distal intestine was several hundred-fold higher than the exo-chitinase activity in stomach tissue. The greatest exo-chitinase activity was found in the distal intestine. The zygomycete-based diet resulted in higher chitinolytic activity in gut tissue compared to the fish meal-based diet. Disturbed intestinal integrity and increased uptake rate of the amino acid lysine were observed in the distal, but not proximal, intestine of fish fed the zygomycete-based feed.
Keywords: Amino acid absorption; Chitin; Intestinal barrier functions; Plasma cortisol; Zygomycetes.
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