A Comparison of Methods to Analyze Particle Size as Applied to Alfalfa Haylage, Corn Silage, and Concentrate Mix

Abstract

Nine different methods to analyze the particle size distributions of feeds 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 various 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 median particle size, respectively. Within-method variation accounted for only 2.3% of the variation in median particle size. The variation explained 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. The effects of method and the interaction of method and feed complicated the comparison of particle size data as analyzed by the various methods. However, employing one of the six remaining methods in future experiments would explain enough of the variation to justify an initial compilation 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.