STANDARDIZATION OF IN-SITU TECHNIQUES FOR RUMINANT FEEDSTUFF EVALUATION

Over the last two decades, in situ techniques have been used extensive ly for measuring ruminal degradation of feedstuffs. Current predictive models put renewed emphasis on the need for quantitative information regarding rates and extents of ruminal degradation. However, in situ t echniques suffer from tremendous variation, both within and among labo ratories. A considerable number of studies have evaluated the influenc e of various factors on in situ-derived estimates of ruminal degradati on. Factors that should be addressed in a standardized procedure inclu de bag and sample sizes; bag material and pore size; sample processing ; animal diet, feeding level, and frequency; bag insertion and removal procedures; location of bags within the rumen and containment procedu res for the bags; rinsing procedures; microbial correction; incubation times; mathematical models; and numbers of replicate animals, days, a nd bags required to obtain repeatable estimates of ruminal degradation . Several recommendations that should increase the precision of in sit u measurements are presented. Currently, the lack of standardization i n rinsing techniques and the failure or inability to correct for micro bial contamination of in situ residues seem to be the major sources of variability with in situ procedures.