Variation in Chromic Oxide Methods of Determining Digestibility of Hand-Fed Beef Cattle Rations

Abstract

Variation in the Cr₂O₃ method of determining digestibility of hand-fed beef cattle rations was studied in two experiments. In the first experiment, the Cr₂O₃ method using three fecal sampling procedures was compared with the total collection method for determing digestibility. Daily variation of Cr₂O₃ in the feces was studied. The second experiment studied the effects of different types of rations, length of sampling period, and moisture condition of feces on the recovery of Cr₂O₃ in the feces. Digestion coefficients calculated from the determination of Cr₂O₃ in the total fecal collection were lower than those calculated from the conventional method. This was because the Cr²O³ was only 95.1% recovered. The Cr₂O₃ grab sample methods resulted in still lower digestion coefficients. The greatest varation in coefficients resulted from using the grab sample methods. The percent Cr₂O₃ in the fecal grab samples varied greatly from day to day. In the second experiment, low energy rations produced by using large amounts of low quality hay resulted in erroneous Cr₂O₃ recoveries. The unusually high percent recoveries probably resulted from the difficulty of mixing Cr₂O₃ in the rations. More accurate Cr₂O₃ recoveries were obtained when the rations contained 39% roughage and when Cr₂O₃ determinations were made on wet fecal samples. Copyright © . .