Functional Development of Rumen Mucosa. I. Absorptive Ability

Abstract

Two Holstein calves were fed milk, alfalfa hay, and starter (MHG); two received milk only (M). Absorption of acetic acid was measured from a test solution, pH 6.6, introduced into the emptied, fistulated rumen. Mean maximum absorption rates (milligrams of acid/100 ml of solution per hour) at 1, 4, 8, and 13 wk of age, respectively, were 30, 163, 179, and 402 for MHG calves and 21, 26, 22, and 22 for M calves. One calf was switched at 19 wk of age from M to MHG; absorption rates at 16, 21, 23, 27, and 36 wk of age, respectively, were 21, 48, 142, 191, and 248. Absorption did not increase in a calf on M up to 34 wk of age. Absorption was decreased in MHG calves by replacing normal rumen contents with saline prior to the absorption study. Employing an additional calf (MHG) to study this effect more extensively, it was found that replacement of saline with a solution of volatile fatty acids (VFA) reduced the depression. Absorption was slower from solutions at pH 7.5–8.0 than from solutions at pH 5.0–5.5 for calves on MHG and M. The absorption rate of VFA decreased as their chain length decreased at acid pH values for calves on MHG and M; at alkaline pH, the results were less conclusive, but a decrease with decreasing chain length also was indicated. Part of the association between absorptive ability and rumen structure probably represents a mutual dependence of these two aspects of rumen development on the metabolic activity of the mucosa. © 1963, American Dairy Science Association. All rights reserved.