Some effects of potassium chlorate administration onin vitroandin vivorumen fermentation

Abstract

SummaryHay was fed to anin vitrocontinuous culture of the rumen microbial population and to sheep kept in metabolism cages, and the effects of potassium chlorate addition on the rumen fermentation were studied. The compound was given for 8 daysin vitroand for either 3 or 8 daysin vivo.Potassium chlorate additionin vitro(13·7 mg/g hay D.M.) depressed the production of CH4and acetate, had little effect on propionate production and caused a small increase in the production ofn-butyrate andn-valerate. The treatment also depressed cellulose digestion and the concentration of DNA in fermentor liquor, but increased the CO2:CH4ratio in fermentor gas.When givenin vivofor 8 days at 6·7 mg/g hay D.M., potassium chlorate progressively depressed total VFA concentration in rumen fluid, had no effect on VFA molar proportions but caused a small increase in the CO2:CH4ratio in rumen gas. When administeredin vivofor 3 days at 14·4–15·3 mg/g hay D.M. the treatment increased the molar proportions of propionate and depressed those of acetate in rumen fluid without affecting total VFA concentration. There were considerable differences between animals in propionate response, and the maximum responses were generally obtained 2–5 days after dosing had ceased. Potassium chlorate addition also caused a temporary reduction in appetite with some sheep.It was concluded that potassium chlorate was toxic to the rumen microbial population when given for 8 days, but that large doses given over 3 days could be used to increase the ratio of propionic acid relative to acetic and butyric acids produced from the rumen fermentation.