Observations on the Use of Chromic Oxide for Estimating the Fecal Output of Dairy Animals

Summary Two trials employing dairy heifers fed either fresh-cut alfalfa (Trial 1) or mixed hay (Trial 2), and one trial using lactating cows which received a complete ration, have been conducted to study further the usefulness of chromic oxide for predicting fecal output. Total fecal collections were made during each trial. In addition, partial fecal samples were obtained at 6 a.m., 12 noon, 6 p.m., and 12 midnight on each day of each collection period. The results indicate that periods of from three to seven days may be required for the indicator to reach a stable level in the feces. The mean recovery rates of chromic oxide from totally collected feces and from the combined 6 a.m. and 6 p.m. samples for Trials 1, 2, and 3, respectively, were 89.4 and 89.7%; 97.5 and 96.4%; 90.0 and 89.7%. Average daily fecal DM outgo was estimated from the chromic oxide concentration of the combined 6 a.m. and 6 p.m. samples, with an error of about 12%. Only in Trial 2 were satisfactory estimates obtained.