Particulate Rumen Turnover Rate Measurement as Influenced by Density of Passage Marker

Abstract

Alterations of estimates of ruminal turnover rate by density, alfalfa fiber chromium concentration, or sampling site were evaluated. Alfalfa fiber density was raised by mordanting with increasing chromium concentrations. Three Holstein cows were fed for ad libiturfi intake equal portions of a total mixed diet three times a day. After a pulse dose of marker, fecal and ruminal grab samples were collected from cows at scheduled intervals for 5 days. Linear regression analysis was used -to measure slopes of declining phase of marker excretion curves. Cell wall densities (g/ml) and ruminal turnover rates (h -t) based on ruminal and fecal sampling sites were: 1.21, .0116, .0236; 1.33, .0525, .0306; and 2.08, .0392, .0485 for alfalfa cell wall with chromium concentrations of 7.01, 38.67, and 56.76 mg/g. Particle density and chromium concentration, but not sampling site, influenced estimates of luminal turnover rate.