Determination of the Fecal Excretion Rate of Horses with Chromic Oxide

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Abstract
The diurnal variation in the excretion of chromic oxide (Cr2O3) was studied in six horses during three digestion trials, using one lot of alfalfa hay in three physical forms (chopped loose, pellets and wafers). The recovery of Cr2O3 averaged 98.4%. The intraday variation of Cr2O3 ranged from 59.8 to 134.8% of the daily mean among defecations of individual horses. The proximate fecal constituents varied less than Cr2O3 and in the descending order of ash, water, crude protein and crude fiber. Their variance did not seem to be related to that of Cr2O3. The interday variation of Cr2O3 and fecal constituents was as great as the intraday variation. Fecal Cr2O3 concentrations varied in a diurnal pattern described by a fourth degree polynomial equation for separate day and night periods. Approximately 64 and 89% of the variation was explained by the mean day and mean night curves, respectively. A sixth degree polynomial accounted for 76% of the variation of the mean day plus night combined curve. The Cr2O3 excretion curve was best described by a sinusoidal periodic function, for which the Fourier coefficients were calculated for two harmonics. The time after administration of Cr2O3 to the horses appeared to be the major determinant for the extinction of the excretion curve, but the night curve showed a higher extinction than the day curve. The phase of the curves was moved when either pellets, wafers or loose hay were fed, indicating a different rate of passage of Cr2O3 with different physical forms. Estimates of fecal excretion rates of horses by the 4-day rectal grab sample method and determination of Cr2CO3 content were similar to results from the 10-day total collection procedure, provided that recovery rate of Cr2O3 was considered. Fecal Cr2O3 samples taken at random for 10 days provided estimates of fecal excretion rates which did not agree with those from the total collection procedures. Copyright © 1966. American Society of Animal Science . Copyright 1966 by American Society of Animal Science

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