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

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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 © . .