Production of volatile fatty acids as a result of bacterial interactions in the cecum of gnotobiotic rats and chickens fed a lactose-containing diet.

Volatile fatty acid (VFA) productions from lactose and lactate by a Clostridium butyricum and a Veillonella alcalescens strain, alone or in combination with a Lactobacillus acidophilus strain, were determined both in vitro in culture media and in vivo in the ceca of gnotobiotic animals. Gnotobiotic rats, which possess intestinal lactase, and chickens, which are devoid of it, were used. Both animal species were fed a diet containing 4% lactose. The in vitro results showed that the C. butyricum strain fermented lactose and D-lactic acid to butyric and acetic acids, whereas L-lactic acid was not fermented. The V. alcalescens strain did not ferment lactose and fermented L better than D-lactic acid. The in vivo results showed that high VFA concentrations were obtained in the ceca of chickens either disassociated with V. alcalescens or C. butyricum and Lactobacillus strains or monoassociated with C. butyricum. VFA concentrations in the ceca of rats were low, whatever strain the rats harbored. In addition, an antagonistic effect of the C. butyricum strain against the Lactobacillus strain was evidenced both in rats and chickens. It is suggested that the absence of a host lactase makes the chick a good model for lactose intolerance studies in human newborns.