Technical note: Evaluation of a scoring system for rumen fill in dairy cows.

Changes in feed intake are useful in early detection of disease in dairy cows. Cost and complexity limit our ability to monitor dry matter intake (DMI) of individual cows kept in loose-housing systems. A 5-point subjective scoring system has been developed to visually describe rumen fill, but no work to date has evaluated these scores as an indicator of feed intake. The objective of this study was to evaluate the performance of within-cow changes in visual rumen fill scores as estimates of changes of DMI and feed intake in dairy cows. Our results illustrate that rumen fill scored on a scale from 1 to 5 has substantial intra- (Cohen's kappa coefficient=0.69) and interobserver (Cohen's kappa coefficient=0.68) repeatability. Within-cow changes in visual rumen fill score are correlated with changes in DMI (Spearman's rank correlation=0.68). The depth of the paralumbar fossa (mean +/- SD; 5.6+/-0.9 cm) changes considerably (up to 4.8 cm) within 70+/-5 min. This more objective measure was also correlated with visual rumen fill scores (Spearman's rank correlation=-0.62). Our results indicate that subjective rumen fill scores are statistically associated with both an objective measure of paralumbar fossa indentation and feed intake. However, much of the variation in visual rumen fill scores is not associated with either measure, suggesting that caution is required in clinical usage of these scores.