'Lactate type' response of ruminal fermentation to chloral hydrate, chloroform and trichloroethanol.

In ruminal fluid, taken from a cow 2 h after cereal feeding and supplemented with powdered grass, chloral hydrate diminished the rate of acetate, butyrate and propionate production. Instead, a considerable increase in lactate production was elicited by the drug. Chloroform and trichloroethanol had the same effect. Chloral hydrate and chloroform rendered the redox potential more negative which indicates inhibition of methane production. A concentration of chloral hydrate (2 mM), giving complete methane inhibition, reduced volatile fatty acid production by 30%. The findings are explained by assuming that chloral hydrate blocks methane production but in addition is inhibitory at a step below lactate in the reductive pathway to propionate and that the conditions chosen resulted in substrate saturation of one of the enzymes in the succinate pathway to propionate.