We. Pinchak et Dp. Hutcheson, EFFECT OF RESTRICTED FORAGE INTAKE IN CONFINEMENT ON ESTIMATED FECAL OUTPUT FROM A SUSTAINED-RELEASE BOLUS, Journal of range management, 45(2), 1992, pp. 129-132
Two experiments were conducted to investigate the effects of restricte
d forage intake on patterns of chromium excretion to determine sample
window duration and the accuracy and precision of fecal output estimat
es derived from the Captec Chrome sustained release bolus. In Experim
ent 1, 8 crossbred steers (xBAR 243 +/- 14 kg) were assigned randomly
to receive prairie hay (PH) at intake levels of either 1.12% body weig
ht (BWT) or 0.75% BWT while maintained in individual metabolism crates
and(or) pens. In Experiment 2, steers from Experiment 1 were rerandom
ized and assigned to receive PH at either 1.12% BWT or alfalfa hay (AH
) at 1.30% BWT. The average post-dosing bolus failure rate across expe
riments exceeded 30%. Estimated fecal output exceeded actual fecal out
put under all experimental conditions (P < 0.08). Averaged across expe
riments, fecal chromium recovery was low (xBAR 55 +/- 4%). When estima
ted fecal output was corrected for mean marker recovery within treatme
nt, it did not differ from actual fecal output (P > 0.60). Treatment e
ffects were similar for estimated fecal output, corrected estimated fe
cal output, and actual fecal output. Under conditions of pen feeding a
nd restricted forage intake, estimated fecal output exhibited treatmen
t differences similar to those of total fecal collection. However, unl
ess adjusted for average marker recovery, these estimates were signifi
cantly greater than actual fecal output.