Digestion of Alfalfa Hay Using Washed Ruminal Bacteria

Abstract

A culture system for digesting forages utilizing washed ruminal bacteria was examined. Cultures inoculated with washed bacterial suspensions had similar cellulolytic populations but lower methane production rates than did cultures inoculated with rumen fluid. Subsequent experiments utilized washed cell suspensions. Urea supplementation (8 mM) increased total bacterial and cellulolytic populations after 24 h of incubation but did not alter methane or VFA production. After incubation, alfalfa hay residues were fractionated by sequential extractions. Soaking hay in buffer alone resulted in a 15% weight loss, mostly from materials extracted by ethanol and .5 M H2SO4. About half of the water-soluble materials were lost within 2 h, pectin within 12 h, and hemicellulose and cellulose digestion began after 12 h. Neutral detergent fiber and oxalate-insoluble material losses were detectable at 6 and 12 h, respectively. Total dry weight decreased throughout incubation. Analysis of extracts indicated that carbohydrate concentrations followed patterns of dry weight losses. Thus, washed bacterial cell suspensions can be used to ferment forages in a rumen-like fashion to study the biochemical processes involved in digestion, which would be limited by intrinsic factors of the forage materials. © 1987, American Dairy Science Association. All rights reserved.