[Effect of DL-lactic acid on voluntary food intake in sheep (author's transl)]

Previous experiments indicate that changes in duodenal fluid concentration of DL-lactic and volatile fatty acids (VFA) influence flow rate of ingesta and may also be a regulating factor of food intake in ruminants. The present experiment was designed to determine the sensitivity of the duodenum to DL-lactic acid and VFA in relation to diets of hay, dried grass or concentrates. On a diet of hay, administration of small amounts of either DL-lactic acid or VFA into the duodenum had no effect. On a diet of dried grass or concentrates the same amount of VFA had no effect but that of DL-lactic acid (12 mM/h) halved the dry matter intake. In animals on a diet of hay and after administration of 40 g of propionate into the rumen, duodenal perfusion of the same quantity of DL-lactic acid produced a similar reduction of food intake. It was concluded that duodenal DL-lactic acid acts as a regulator of food intake possibly via the propionate metabolism pathway.