Accuracy of Roughage Intake Estimations as Determined by a Chromic Oxide-In Vitro Digestibility Technique

Abstract

Intakes of roughage rations by two-year-old cows and heifers were estimated by a chromic oxide dilution technique and compared against actual measured levels of intake. Intake was overestimated 2.9 percent in cows and 28.6 percent in heifers. Linear regression was used to increase accuracy of intake estimates by developing equations to predict actual intake from values obtained by the indicator dilution approach. A system for using this approach under range conditions was suggested. It was shown that non-adjusted intake estimates were not absolute values and the assumption that estimated intake values are relative and adequate for comparison is valid only when ruminants consume similar diets.