Livestock Management
2016 Feed Composition Tables: How to Discover
the Nutritional Value of 280 Cattle Feedstuffs Compiled by R.L. Preston, Ph.D.
N
utrition research spanning more than 125 years has defi ned the nutrients required by animals.
Using this information, diets can be formulated from feeds and ingredients to meet these requirements with the expectation that animals will not only remain healthy but also will be productive and effi cient. The ultimate goal of feed analysis is to predict the produc- tive response of animals when they are fed diets of a given nutrient composition.
Table values for feed composition Feeds are not of constant composition. Unlike chemi-
cals that are “chemically pure” and thus have a constant composition, feeds vary in their composition for many reasons. An actual analysis of a feed to be used in a diet is much more accurate than the use of tabulated composition data. Actual analysis should be obtained and used whenever possible. What is the value, then, of showing composition
data for feeds? It is often diffi cult to determine actual composition in a timely way and therefore tabulated data are the next best source of information. In using tabulated values, one can expect organic
constituents (e.g. crude protein, ether extract and fi ber) to vary as much as ±15 percent, mineral constituents
68 The Cattleman January 2017
to vary as much as ±30 percent and energy values to vary up to ±10 percent. Thus, the values shown can only serve as guides. That’s why they are called “typical values.” They are not averages of published information, however, since judgment was used in arriving at some of the values in the hope that these values will be more realistic for use in formulating cattle and sheep diets. New crop varieties may result in nutrient composi-
tion changes. Genetically modifi ed crops may result in feeds with improved nutrient content and availability and/or decreased anti-nutrient factors. Changes in processing procedures can change the nutrient com- position of by-product feeds.
Chemical constituents vs. biological attributes of feeds Feeds can be chemically analyzed for many things
that may or may not be related to the response of ani- mals when fed the feed. The response of cattle and sheep when fed a feed, however, can be termed the biological response to the feed that is a function of its chemical composition and the ability of the animal to derive useful nutrient value from the feed. The latter relates to the digestibility or availability of a nutrient in the feed for absorption into the body
thecattlemanmagazine.com
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