Abstract
Twelve Holstein calves were fed on whole milk, and were administered by acetic, propionic and butyric acid, individually and as equimolar mixture or as 6:3:1 mixture, through the rumen cannula twice a day from 3 to 13 weeks of age, to determine the effect of the intraruminal constitution of volatile fatty acids on the metabolic activity of the rumen epithelium. The calves were sacrificed at the end of 13 weeks of age. Epithelium from the anterior dorsal blind sac was separated from the muscle layer. Two g of the rumen epithelium was incubated at 38°C for 3 hours in KREBS-RINGER bicarbonate medium at pH 7.2 in a 95:5 atmosphere of oxygen and carbon dioxide. Two hundred μ moles of acetate, propionate, butyrate, and an equimolar mixture of these three acids were added to medium.
Butyrate was the best substrate to be metabolized by the rumen epithelium from the all calves used. The amount of each volatile fatty acid metabolized was, in descending order, butyrate, acetate and propionate in all trials. It seems that the utilization of volatile fatty acids by the rumen epithelium of the young calves increased in a situation of the preferential utilization of butyric acid, independently of the intra-ruminal constitution of volatile fatty acids.
