NUTRITION
PIH-3
pork industry handbook
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA
Energy for Swine
Authors
Palmer Holden, Iowa State University
Lowell Frobish, Clemson University
James Pettigrew, University of Minnesota
Reviewers
Herbert M. Barnes, Ohio State University
Bill G. Diggs, Mississippi State University
Pigs require energy to maintain normal body processes, to grow, and to reproduce. Feeds supplying energy are major components of all swine diets, and the quantity of diet voluntarily consumed by pigs is related to its energy content. Carbohydrates from cereal grains are the most abundant energy source in swine diets. Fats and oils contain more energy than carbohydrates per unit weight but are included to a lesser extent. Amino acids, or protein, may serve as an energy source only if included in the diets in excess of animals' requirement for protein synthesis.

The value of a feedstuff is based on several factors besides its energy content. Among these are: acceptability (how well the material will be consumed by an animal), availability of energy, and the feed’s contribution of other nutrients (protein or amino acids, vitamins, minerals). Should a swine producer buy corn, wheat, or oats as a feed ingredient? This will depend primarily on the cost of these ingredients and their value as sources of energy and other nutrients for the pig.
Definition of Energy
To make sound decisions in selecting feed ingredients it is desirable to have an understanding of the system by which feedstuffs are rated for their energy content and the use of these ratings toward meeting the energy requirements for pigs' growth and production. The gross energy (GE) of a feed ingredient is defined as the heat produced when a substance is burned. It is expressed as calories per unit weight. A calorie is the amount of heat required to raise the temperature of 1 gram of water from 14.5 to 15.5 degrees C. A kilocalorie (kcal) is 1,000 calories, and a megacalorie (meal) is a million calories.

Not all of the feed consumed is digested and absorbed. Some energy is lost in the fecal material (Fig. 1). Thus, GE is a poor estimate of energy for the pig. The amount of energy remaining after subtracting the fecal energy loss from total energy intake is designated as digestible energy (DE). The difference between GE and DE may be large. The greater the digestibility of energy

Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U. S. Department of Agriculture Cooperating. H. A. Wadsworth, Director, West Lafayette, IN. Issued in furtherance of the Acts of May 8 and June 30, 1914. It is the policy of the Cooperative Extension Service of Purdue University that all persons shall have equal opportunity and access to its programs and facilities without regard to race, color, sex, religion, national origin, age or handicap.