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Excretion of Chromium Oxide by Dairy Cows

Department of Animal Husbandry, Cornell University, Ithaca, N. Y.

ABSTRACT

An experiment was conducted to study the effects of feeding schedule and various ratios of forage to concentrates upon the excretion pattern of Cr₂O₃. The indicator was administered once daily to Holstein cows consuming rations containing from 35 to 100% roughage. Fecal samples were taken every 2 hr. during the first two periods and every 3 hr. during the last two periods. Chromium oxide per gram of fecal dry matter was determined on all samples.

A symmetrical excretion pattern was observed when average values were plotted, and an equation was fitted to the excretion curve. There was considerable variation in relative Cr₂O₃ concentration at any sampling time, indicating the importance of obtaining a large number of samples; however, neither the feeding schedule nor the proportion of roughage to concentrate had an influence upon the general character of the curve.

It was concluded that time of Cr₂O₃ administration was of primary importance in respect to time-concentration relationships of fecal Cr₂O₃, and that so-called physiological, diurnal effects were of little importance. The data suggest that a 12-hr. sampling procedure would be more accurate than unequal fecal sampling times.

¹ Present address: USDA, ARS, Animal Husbandry Research Division, Beltsville, Maryland.