Comparative effects of dietary Na+-lactate on Arctic char, Salvelinus alpinus L., and Atlantic salmon, Salmo salar L.

Abstract

Arctic char, Salvelinus alpinus L., and Atlantic salmon, Salmo salar L., were fed a commercial diet with or without supplementation of 1.5% Na+-lactate. Dietary Na+-lactate enhanced growth of Arctic char, while that of salmon was unaffected. Dietary 14C-lactate was retained for significantly longer in the stomach of Arctic char than that of Atlantic salmon. Changes in intestinal cholytaurin hydrolase activity, a bacterially produced enzyme, may indicate that dietary lactate affects the intestinal microbiota of Arctic char but not that of Atlantic salmon. Analysis of bile acids of char showed that dietary Na+-Iactate influenced neither intestinal nor gallbladder bile acid composition. Although Arctic char possesses the classical entero-hepatic circulation pathway, no extra loss of bile acids from the fish was observed. It is concluded that the retention time of diet in the stomach of char is significantly longer than that of salmon. This may increase the antibacterial action of lactate in the former, favouring the colonization of lactic-acid-tolerant bacteria in the intestinal tract, some of which produce the enzyme cholytaurin hydrolase.