Functional Development of Rumen Mucosa. II. Metabolic Activity

Abstract

The objective of the present study was to determine the effect of diet on metabolic activity of rumen mucosa. Three Holstein calves were fed milk (M) and three received milk, hay, and grain (MHG). The calves were sacrificed at 16 wk of age. Mucosa from the anterior dorsal sac was stripped from the muscle and placed temporarily in ice-cold Ringer. Two-gram samples were incubated at 39 C for 3 hr in Krebs-Ringer-bicarbonate buffered at pH 7.2 in a 95:5 atmosphere of oxygen and carbon dioxide. Two hundred micromoles of acetate, propionate, butyrate, an equimolar mixture of these three, or glucose, were added to the medium. Mean uptake of these substrates was (micromoles per 100 mg dry tissue per 3 hr) 5.9, 29.6, 44.1, 31.5, and 3.8, respectively, for MHG calves and 2.9, 5.8, 4.7, 5.8, and 4.2, respectively, for M calves. Ketones were produced from acetate, butyrate, and the equimolar mix. Percentage conversion of acetate and butyrate to ketones was 72 and 88, respectively, for MHG calves and 17 and 29, respectively, for M calves. The relationship of the metabolic activity to the structural development and absorptive ability of the rumen mucosa is discussed. © 1963, American Dairy Science Association. All rights reserved.