EFFECT OF FREQUENCY OF ADMINISTRATION OF CHROMIC OXIDE ON ITS FECAL EXCRETION PATTERN BY GRAZING CATTLE

A total of 20 gm. daily of chromic oxide (Cr 2 O 3 ) in gelatin capsules was administered to grazing steers and dairy cows. This daily dose was given (a) in a single dose at 8 a.m., or (b) in two equal doses at 8 a.m. and 4.30 p.m., or (c) in six equal doses at 4-hour intervals. The Cr 2 O 3 excretion patterns were determined from grab samples of feces.When animals were dosed once or twice daily, Cr 2 O 3 concentration in the feces changed significantly during the day. When animals were dosed six times daily, Cr 2 O 3 was excreted at a constant rate which could be estimated from a fecal sample taken at any time during the day.Marked differences were observed in excretion patterns obtained in these experiments and under similar conditions by other investigators. These differences emphasize the difficulty of reproducing the Cr 2 O 3 excretion cycle of grazing cattle. The implications of this phenomenon are discussed in relation to the accuracy of measuring fecal output of grazing animals.