Short-chain fatty acids in germfree mice and rats

Abstract

The short-chain fatty acids (SCFAs) have been analyzed in small intestinal and cecal content of 10 germfree and six conventional mice from a Norwegian laboratory, in cecal content and serum of five germfree rats and two germfree mice from a Swedish laboratory and in Norwegian and Swedish autoclaved, nonpurified rodor diets. The mean total SCFA concentration was 1020 μmol/kg in cecum and 1010 μmol/kg in small intestine of Norwegian germfree mice; 124,600 μmol/kg in cecum and 6,250 μmol/kg in small intestine of conventional mice; 490 μmol/kg in cecum and 370 μmol/L in serum of Swedish rats; 360 μmol/kg in cecum and 290 μmol/L in serum of Swedish mice, 31.4 mmol/kg in Norwegian and 19.5 mmol/kg in Swedish nonpurified diets. Acetic acid accounted for more than 90% of the total concentration in all samples from germfree animals and diet, but detectable concentrations of propionic, isobutyric, n-butyric, isovaleric and n-valeric acid were also present. Thus, germfree animals have low, but measurable, concentrations of SCFAs in intestinal content compared to conventional animals. Most probably these acids originate mainly from the diet.