Caecotrophy-dependent changes in the metabolic fate of D(-) lactic acid in rabbits

In rabbits the influence of the reingestion of special faeces on gastric as well as on intermediary metabolism of [U-14C]-D(-) lactic acid has been studied. In unrestrained animals there was no naturally occurring D(-) lactic acic concentration measurable either in stomach contents or in blood. Orally loaded D(-) lactate was almost completely decomposed in the stomach and absorbed within 15 min. Thereby intermediary oxidation was equally affected. Thus, in rabbits prevented from caecotrophy the exhalation rate of 14CO2 derived from [14C]-D(-) lactic acid at 2 h after oral application was reduced to about 65% of the rate of unrestrained animals. Similar low oxidation rates have been obtained only if [14C]-D(-) lactate was injected intraperitoneally. One can conclude from these experiments that caecotrophy in rabbits prevents the accumulation of D(-) lactic acid in the stomach by rapid bacterial transformation but increases the rate of its intermediary oxidation by absorption of these transformation products.