Rate of Passage of Chromic Oxide and Composition of Digesta along the Alimentary Tract of Wethers

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Abstract
Six wethers were fed 1500 gm./day of pelleted alfalfa. The rate of passage of Cr2O3 incorporated as a component of paper and as a powder in rations was determined. Chromic oxide “powder” was excreted significantly faster than “paper”. The wethers were put on a 10-day digestion trial, and coefficients obtained by the conventional method agreed with those obtained by the ratio technique using Cr2O3 “paper”. Low recovery of the “powder” was noticed in all runs. The levels of Cr2O3 paper and crude fiber in the feces were correlated significantly. Following the digestibility trial the wethers were slaughtered 10 to 12 hours after the last feeding and the alimentary tract contents removed in 13 sections. The digesta from each section was analyzed for dry matter, ash, Cr2O3, calcium, phosphorus, protein, crude fiber and lignin. Indigestibilities of these feed constituents were calculated using Cr2O3 “paper”, Cr2O3 “powder”, and lignin techniques. Chromic oxide apparently was passed out of the rumen faster than lignin or the bulk of the dry matter. The rate of flow of calcium and Cr2O3 appeared to be very similar. Indigestibilities and levels of lignin and crude fiber showed a high degree of association of these constitutents in their rate of flow through the tract. The concentrations of phosphorus did not follow those of calcium.