A new analytical procedure to replace the outdated Weende proximal feed ingredient analysis paradigm is long overdue
Gene M. Pesti
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Abstract
Proximate analysis is also called the Weende method. It has been the standard used for describing the chemical composition of feed ingredients for the past 150+ years. Understanding of the chemical composition of feeds has changed greatly in that time. Most of the current terms used for proximate analyses are unclear and misleading: (1) Crude protein, nitrogen × 6.25 describes true protein plus any other nitrogen-containing compounds including nucleotides and even phospholipids. (2) Crude fibre represents approximately half of the true fibre in most ingredients, but only approximately one-seventh of the fibre in important ingredients like soybean meal. (3) Ether Extract represents the neutral lipids in ingredients but little of the polar lipids like the lecithins. (4) The Nitrogen-free Extract is not an extract at all. It is supposed to represent starch in feed, but it contains large proportions of pectin, hemicellulose and even some cellulose. It reflects the error in Crude Fibre. Inadequacies of the Weende system have been known for a very long time. Animal producers desire to embrace modern technology and adapt more precise feeding techniques.
This paper explains how 19th century chemistry relates to 21st century understandings of feed composition and proposes an updated method of feed ingredient analysis.
A new method of describing feed composition based on 13 modern chemical categories was conceived and called the ‘Armidale Method’, to distinguish it from the Weende method. The new feed chemical category method was used to compile a preliminary database based on: moisture, sugars, oligosaccharides, starch, pectin, hemicellulose, cellulose, lignin, ash, neutral lipids, polar lipids, true protein, and nonprotein nitrogenous compounds.
Composition values for 26 ingredients compiled from three sources averaged 1032.0 ± 49.5 g/kg, comparable to the theoretical 1000 g/kg.
The Armidale Method of analyses could be the starting point for discussions of new standardised procedures for ingredient trade and feed formulation.
It is time for producers, in conjunction with nutritionists and analytical chemists, to explore the best ways to represent the composition of feed ingredients for feeding value and trade.
Keywords: Armidale method, crude protein, feed analysis, food analysis, paradigm, proximate analysis, true protein, Weende method.
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