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New Version of Nutrient Requirements of Beef Cattle

Livestock Update, August 1996

Mark L. Wahlberg, Animal and Poultry Sciences

The National Research Council (NRC) has just produced and released the seventh edition of Nutrient Requirements of Beef Cattle. The last revision was published in 1984. I believe the current version makes giant leaps ahead in defining and quantifying the factors which influence the nutritional needs of beef cattle.

The document consists of two major components, a 242-page book and a computer diskette. In the book is 100 pages of literature review on 8 different major topics. A table of feed composition is included that gives not only average values but an estimate of the range in composition and the effects of processing methods .

There is approximately 70 pages in the book which is a users guide for the computer diskette. The diskette contains two different models that the user can choose. One is for evaluation and prediction of performance on a given diet, the other is to model the use of nutrients for various physiological processes. The computer models utilize current knowledge of factors which affect the nutritional needs of cattle and enables the user to define these factors to customize the situation for a specific feeding program. The user can print a table of requirements for the specific situation modeled.

The factors considered are amazingly detailed. For growing- finishing cattle they include:

Description of the Animal
and Environment
Description of Management
Current Weight
Breeding System
Dam's Breed
Sire's Breed
Finished Weight and Grade
Condition Score
Additives & Implants
Pasture or Drylot
Wind Speed
Air Temperature
Night Cooling?
Hair Condition
Heat Stress?
Hide Thickness

The factors for the Cow-Calf enterprise are:

Description of the Animal
and Environment
Description of Management
Same as above plus ...
Days Pregnant
Days in Milk
Lactation Number
Peak Milk Production
Duration of Lactation
Milk Composition
Age at First Conception
Calving Interval
Expected Calf Birth Weight
Same as Above

Tables of nutrient requirements as structured in the 6th edition are not printed in the book. A table of requirements for an "average" animal are included, and the Appendix includes adjustment factors for most of the factors cited above. The computer method of determining requirements is strongly recommended, however.

This material is available from National Academy Press. See hard copy of Livestock Update for ordering information and price.

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