DIURNAL EXCRETION OF Cr2O3 BY RUMINANTS WHEN ADMINISTERED IN SUSTAINED-RELEASE PELLETS

Abstract

Two types of sustained-release pellets (S.R.P.) were developed for administering chromium oxide (Cr2O3) to cattle and sheep: an extruded pellet (E.S.R.P.) for cattle, dissolution time 4 to 5 days, containing about 10 g Cr2O3, and a pressed pellet (P.S.R.P.), dissolution time 16 to 20 days, containing about 32 g Cr2O3 for cattle and 20 g for sheep and calves. Both types of pellets were retained by animals kept indoors and fed either long or chopped forage. Animals on pasture regurgitated 50% or more of E.S.R.P. and about 10% of P.S.R.P. Specific gravity of E.S.R.P. was 1.7 and of P.S.R.P., 2.8.Administration of Cr2O3 in S.R.P. eliminated the statistically significant diurnal excretion cycles normally observed with conventional once or twice daily dosing of animals in stalls. Small but statistically significant (P < 0.05) differences between grab samples of feces occurred with cattle on pasture grazed by free, strip, or mechanical (zero) systems.Sustained-release pellets are useful in experiments with animals kept in confinement but more general use is restricted because they cannot be made by commercial tabletting equipment and may be regurgitated by animals on pasture.