NUTRITION
PIH-7
pork industry handbook
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA
Principles of Balancing a Ration
Authors
J. R. Jones, North Carolina State University
J. C. Rea, University of Missouri
L. J. Johnson, North Dakota State University
Reviewers
Marvin Heeney, Colorado State University
Leland Tribble, Texas Tech University
Wendell Moyer, Kansas State University
A balanced ration contains the necessary nutrients in the correct proportions to nourish the animal properly. The ration nutrients are energy, protein, minerals and vitamins. Fat is also required to supply essential fatty acids but is usually adequate in all practical rations. Water is even more important than energy but normally is provided with free access and is not involved in ration formulation. A palatable and economical energy source can be transformed into a nutritionally balanced ration if the nutrient deficiencies are corrected.

Practical ration formulas must be sufficiently flexible to accommodate price and feedstuffs availability while retaining the necessary nutritive balance and adequacy. When supplements are extremely high priced, it may be most economical to feed slightly less protein than recommended even with a somewhat decreased rate of production. When protein-rich feeds are relatively cheaper than those low in protein, it is sometimes economical to supply a greater amount of protein than normally supplied.

Swine rations are usually formulated around cereal grains because they are high in energy and low in fiber. Corn is the most commonly fed grain, but other grains may be used. All grains are deficient in protein quantity and quality and in minerals and vitamins. Corn is an excellent energy source, and soybean meal is an excellent protein source. Soybean meal can be fed as the only supplemental protein source for swine.

The nutrient content of grains is affected by such factors as type or variety, soil and climatic conditions, stage of maturity at harvest, location where grown and time in storage. Nutrient requirements vary in animals by age, weight, sex and function. Requirements may vary even in animals of the same weight. Therefore, rations are usually over-fortified as insurance against the variation that exists in both feeds and animals.
Usually high-energy, low-fiber rations are used for swine, and energy level is not a particular problem for growing-finishing animals. However, for gilt developer or gestation rations, lower energy and higher fiber levels can be used to control weight.
Logical Steps in Formulating a Ration
1.	Identify the animals to be fed.
2.	Select nutrient allowances to fit the animal.
3.	Select ingredients to meet nutrient allowances.
4.	Determine amounts of each ingredient.
Identify animals to be fed by age and function and specific conditions under which they are fed. Penning and feeding in uniform lots allows a producer more accurately to meet the pigs’ requirements.

Select a set of nutrient requirements or allowances most appropriate for the animals being fed. An authoritative source of information is “Nutrient Requirements of Swine” published by the National Academy of Sciences. Adaptations from this publication mostly revised upwards are presented in Tables 1 and 2, and are called allowances. Nutrient allowances may differ from requirements and may reflect special area or regional needs, or even opinion. Table 3 gives some conversion factors that are very useful in ration calculations.

Select suitable ingredients to insure that the ration is nutritionally balanced, palatable, safe and economical. Table 4, “Maximum amount of different feeds for various rations,” gives some guidelines for utilizing different feeds. Various feeding guides and example rations are helpful in selecting feed ingredients. Average analyses of selected ingredients are presented in Table 5.

Determine the necessary fixed amounts of certain ingredients (minerals and vitamins) and then mix grain(s)
Cooperative Extension Work in Agriculture and Home Economics, State ot Indiana, Purdue University and U. S. Department of Agriculture Cooperating. H. G. Diesslin, 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.