This year, BEEF will provide the table listing the “Typical Composition of Commonly Used Feeds for Cattle and Sheep” as a downloadable PDF file here at www.beef-mag.com (just click here). These table listings show the typical composition of feedstuffs and ingredients commonly used in the feeding of cattle and sheep in North America.
What's the purpose of this information? Nutrition research spanning more that 100 years has defined the nutrients required by animals. Using this information, diets can be formulated from feedstuffs and ingredients to meet these requirements with the expectation that animals will not only remain healthy but productive and efficient.
The ultimate goal of feedstuff analysis is to predict the productive response of animals when they are fed diets of a given composition. This is the real reason for information on feedstuff composition.
Feedstuffs vary in composition, unlike chemicals that are “chemically pure,” and therefore have a constant composition. Feeds vary in their composition for many reasons. What is the value, then, of showing composition data for feedstuffs?
No one will argue that 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. Often, however, it's either impossible to determine actual composition or there's insufficient time to obtain the analysis. Tabulated data are the next best source of information.
When tabulated data are used, understand that feeds vary in their composition. Using the data shown in the table, one can expect the organic constituents (e.g., crude protein, ether extract, crude fiber, acid detergent fiber and neutral detergent fiber) to vary as much as ±15%, the mineral constituents to vary as much as ±30% and the energy values to vary up to ±10%.
Therefore, values shown can only be guides. For this reason they are called “typical values.” They are not averages of published information, since judgment was used in arriving at some of the values in the hope that these values will be realistic for use in formulating cattle and sheep diets.
Feeds can be chemically analyzed for many things that may or may not be related to the response of an animal when fed the feed. Thus, in the tables on www.beef-mag.com, certain chemical constituents are shown.
The response of cattle and sheep when fed a feed, however, is 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 and its ultimate efficiency of use depending upon the nutrient status of the animal and the productive or physiological function being performed by the animal.
Thus, ground fence posts and shelled corn may have the same gross energy value, but they have markedly different useful energy value when consumed by the animal.
Therefore, the biological attributes of a feed have much greater meaning in predicting the productive response of animals but are more difficult to accurately determine. This is because there is an interaction between the chemical composition of a feed with the digestive and metabolic capabilities of the animal being fed.
Biological attributes of feeds are more laborious and costly to determine and are more variable than chemical constituents. They are generally more predictive, however, since they relate to the response of an animal being fed the feed or diet.
The tables available online at www.beef-mag.com contain composition values for 265 feeds and ingredients. For each feed, its composition is given in terms of dry matter, energy value (TDN, NEM, NEG, and NEL), crude protein, undegradable intake protein (UIP; rumen by-pass protein), fiber (crude fiber, ADF, NDF and eNDF), fat, ash, calcium, phosphorus, potassium, chlorine, sulfur and zinc.
In addition, a write-up accompanies the tables. This provides background information that will be useful on how compositional values can be used in formulating and assessing diets for cattle and sheep.
Readers are encouraged to access and download these tables at www.beef-mag.com to formulate better diets for cattle and sheep.
Editor's Note: Since 1957, R.L. Preston has taught and conducted animal nutrition research in the areas of protein, minerals, growth and body composition. He also has conducted cattle feeding research on the energy value of feeds, growth promotants and nutrition management.
Preston has been a member of the NRC Committee on Animal Nutrition and president of the American Society of Animal Science. Retired as emeritus professor from Texas Tech University, where he was Horn Distinguished Professor and held the Thornton Endowed Chair, Preston's current address is 191 Columbia Court, Pagosa Springs, CO 81147-7650.
Look for the complete tables at www.beef-mag.com