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Chromic Oxide as an Index of Digestibility of All-Concentrate Rations for Sheep¹

University of Georgia^,3, Athens

Abstract

The Cr₂O₃ method was compared with the total collection method for determining digestibility of organic matter or dry matter in all-concentrate rations fed in two experiments to sheep. In the four trials of the first experiment, single samples after 4 days of Cr₂O₃ feeding were employed to compare the organic matter digestibility. In the second experiment dry matter digestibility calculated from total collection was compared with that obtained for the Cr₂O₃ content of fecal samples taken on the fifth through the eighth days, the eighth day, and the eighth through the 11th days after beginning Cr₂O₃ feeding.

Digestion coefficients for dry and organic matter were quite high for sheep. In experiment I digestion coefficients for organic matter by the total collection method were significantly (P<.01) higher than those by the Cr₂O₃ method. The standard errors were lower by the total collection method in three of the four trials, but these were not significant.

In experiment II higher average coefficients also resulted from the total collection method than from the Cr₂O₃ indicator methods, but the differences were not significant. Coefficients calculated from the Cr₂O₃ content in the total fecal samples, in the samples obtained on the fifth through the eighth days and in the samples from the eighth through the 11th days were significantly (P<.05) more variable than those based on the four fecal samples obtained on the eighth day. Coefficients calculated from a composite of four samples obtained the eighth day after beginning Cr₂O₃ feeding were slightly but significantly lower than those obtained by total collection. The comparable standard errors, however, suggest that the method would be appropriate for digestibility comparisons between rations.

¹ Journal Paper No. 423 of the College Experiment Station of the University of Georgia, College of Agriculture Experiment Station.

² The authors are grateful to Chas. Pfizer and Company, Inc., New York and the Ralston Purina Company, St. Louis, Missouri, for supplying some of the ingredients. Acknowledgment is also due J. V. Mason for the laboratory analyses, J. D. Morton for veterinary assistance and J. L. Carmon for statistical assistance.

³ Department of Animal Science.