Caution concerning the Stained Particle Technique for Determining Gastrointestinal Retention Time of Dietary Residues

Three different size particles of ground alfalfa hay were stained different colors and fed together in a single meal. Stained fecal particles were collected on either a 40- or a 60-mesh sieve for subsequent counting and calculation of the mean retention for each size feed particles' residue. Mean retention times based on counting fecal particles collected on the 60-mesh sieve as compared to the 40-mesh sieve were significantly less for the smaller size feed particles and not significantly different for the two larger size feed particles. These results are discussed in relation to the possible influence of size of fecal particle collected and counted upon the determination of mean retention time of feed particles.