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The Magnitude of Certain Sources of Variability in Digestibility Data¹

West Virginia University and University of North Carolina

Abstract

A compilation of published digestibility data was studied statistically in order to discern the relative importance of certain sources of variations.

It was found that 25 to 45 percent of the within-feed variance in digestibility is associated with variations in proximate composition. The amount associated with authors was 20 to 40 percent, that with samples of feed 20 to 35 percent, and that with trials 10 to 25 percent.

It was further found that the variability in digestibility of a given nutrient tends to be inversely related to the content of that nutrient in the feed. Especially high variances were noted for the digestibilities of ether extract, of crude protein in certain roughages, and of crude fiber in concentrates.

The "by-difference" method of determining digestibility gave much higher values for certain components of variance than did the method in which feeds are fed alone. Certain species of animal were found to digest certain nutrients more variably than do others.

¹ Supported in part by a grant from Swift & Company. Published with the approval of the Director, West Virginia Agricultural Experiment Station, as Scientific Paper No. 417.

² West Virginia University.

³ Institute of Statistics, University of North Carolina (Raleigh Campus).