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Organic Acid Concentrations in the Gastrointestinal Tract of Wild-Caught and Cultured Ayu (Plecoglossus altivelis) and Wild-Caught Seema (Oncorhynchus masou)

Abstract

The aim of the present study was to measure organic acid, especially lactic acid, concentrations in contents of the stomach and intestine of wildcaught and cultured ayu (Plecoglossus altivelis) and wild-caught seema (Oncorhynchus masou), and of the stomach as well as anatomically defined three intestinal segments of wild ayu. The concentration of total SCFA in the present study was approximately one–tenth that in the mammalian hindgut. The organic acid concentration did not vary much among fish categories. Lactic, acetic, formic, succinic and propionic acids, but not n-butyric, isobutyric or iso-valeric acids were detected. Lactic acid concentration was by far higher than those of other organic acids. Organic acid concentratios were higher in all intestinal segments than in the stomach of wild ayu. The above results showed that lactic acid is the main product of the microbial breakdown of carbohydrates in the gut of florivorous (wild ayu), omnivorous (cultured ayu) and faunivorous (wild seema) teleosts and that the intestine is the main site of microbial breakdown of carbohydrates to organic acids, at least in wild ayu.

Hisashi Komatsu and Takashi Sakata

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