A COMPARISON OF METHODS TO ANALYZE PARTICLE-SIZE AS APPLIED TO ALFALFA HAYLAGE, CORN-SILAGE, AND CONCENTRATE MIX

Nine different methods to analyze the particle size distributions of f eeds were compared based on results for duplicate samples of the same alfalfa haylage, corn silage, and concentrate mix containing primarily ground corn and soybean meal. The nine methods have been used by vari ous laboratories. Median particle sizes for each sample were analyzed using a nonparametric (rank transformation) procedure to estimate the effects of method, feed, and the interaction of method and feed. These factors accounted for 20.0, 65.1, and 12.6% of the variation in media n particle size, respectively. Within-method variation accounted for o nly 2.3% of the variation in median particle size. The variation expla ined by feed was increased to 78.3%, and that explained by method was reduced to 7.2%, by deleting data for three of the studied methods. Th e effects of method and the interaction of method and feed complicated the comparison of particle size data as analyzed by the various metho ds. However, employing one of the six remaining methods in future expe riments would explain enough of the variation to justify an initial co mpilation of particle size and associated animal response data for use in diet formulation. Accuracy could be improved by the use of a fixed analytical method in all laboratories. The interaction of method and feed deserves additional research.