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Submitted to: Journal of Association of Official Analytical Chemists International
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/2/2008 Publication Date: 1/15/2009 Citation: Hall, M.B. 2009. Determination of Starch, Including Maltooligosaccharides, in Animal Feeds: Comparison of Methods and a Method Recommended for AOAC Collaborative Study. Journal of Association of Official Analytical Chemists International. 92:42-49. Interpretive Summary: There is increased interest in evaluating dietary carbohydrates in livestock diets for their impact on performance and health and for the formal labeling of livestock feeds for their carbohydrate content. For ruminants such as dairy cattle, starch is of particular interest. However, there is presently no official method for analyzing starch in animal feeds. Without an official method, feeds cannot be labeled for starch content, denying consumers information they could use for selecting feeds for their animals. There are many starch analyses available, but they differ greatly in their accuracy and ease of use. We evaluated five starch assays and have recommended one to be tested as an official method. The selected method is sufficiently robust in that it should give commercial feed and research laboratories a sound assay with which to measure feed starch content. This information will be useful to livestock producers, nutritionists, veterinarians, and researchers for formulating diets to enhance livestock performance, health, and efficiency. Technical Abstract: Discontinued production of the enzyme, Rhozyme-S, (required for AOAC method 14.075) invalidated this method for starch in animal feeds and necessitated a search for another assay. Although many starch methods are available, they vary in accuracy, replicability, and ease of use. Five enzymatic-colorimetric starch assays were evaluated that differed in gelatinization method, number of reagents, and sample handling. Methods requiring hot or cold gelatinization with alkali and neutralization were abandoned as they gave no advantage compared to other methods. Remaining assays used thermostable, alpha-amylase and amyloglucosidase, and gelatinization with heating in water, MOPS, or acetate buffer, with subsequent addition of acetate buffer in the first two. The acetate buffer-only method was performed in sealable vessels with dilution by weight; it gave greater starch values (1 to 5 percentage units of dry matter) on starchy substrates than did other methods. This method is a viable candidate for a collaborative study. |
