Exretion of chromic oxide administered in paper to steers fed prairie hay.

T H E value of chromic oxide (chromium sesquioxide) as an indicator for estimating fecal output of sheep and cattle is dependent upon its concentration at a given sampling time providing the basis for estimating a standard recovery. However, chromic oxide excretion rate exhibits a diurnal variation (Hardison et al., 1959; Kane, Jacobson and Moore, 1952) which apparently precludes choosing a desirable single sampling time. As a means of obviating as much of this diurnal variation as possible, the use of chromic oxide as a component of shredded paper has been proposed by workers at the Rowett Research Institute (Corbett, Greenhalgh and MacDonald, 1958). These and other studies by the same authors have indicated that the administration of chromic oxide in shredded paper significantly reduces the variability of its excretion. With shredded paper the chromic oxide was probably released from many places in the rumen rather than from one position as is likely with many of the other forms of administration. The purpose of this experiment was to study recovery of chromic oxide when administered daily or on alternate days as a component of shredded paper. The time period necessary for attaining equilibrium in chromic oxide intake and excretion and the diurnal variation in chromic oxide excretion was also determined.