Estimation of Fecal Output and Particulate Passage Rate with a Pulse Dose of Ytterbiumlabeled Forage

Abstract

Twelve rumen-cannulated lambs (avg. wt. 40 kg), fed long-stem alfalfa or prairie hay in a crossover design (two, 15-day periods) were used to compare estimates of fecal output from a pulse dose of ytterbrium (Yb)-labeled forage and fecal collection bags. Estimates of fecal output (g/day) with Yb-labeled forages were not different (P > .05) from total collection values for lambs fed either alfalfa or prairie hay. Fecal output from a pulse dose of Yb was 100 .+-. 2% of total collection for lambs fed alfalfa and 103 .+-. 3% for lambs fed prairie hay. Particulate passage from the rumen was faster (P < .01) in lambs fed alfalfa (6.0%/hr) then in lambs fed prairie hay (3.9%/hr). A pulse dose of Yb-labeled hay appears to prove reliable estimates of fecal output as well as passage rate estimates, but validation of techniques in free-grazing ruminants is needed.