NUTRITION
PIH-7
pork industry handbook
PURDUE UNIVERSITY • COOPERATIVE EXTENSION SERVICE • WEST LAFAYETTE, INDIANA
Principles of Balancing Swine Rations
Authors
James R. Jones, North Carolina State University
M. Terry Coffey, North Carolina State University
John C. Rea, University of Missouri
Reviewers
Kofi Boeteng, College of the Virgin Islands
Dale Forsyth, Purdue University
William Hugh, University of Hawaii
Leland Tribble, Texas Tech University
A balanced swine ration contains the necessary nutrients in the correct proportions to nourish the animal properly. Required nutrients are energy, amino acids, minerals, and vitamins. Fat is also required to supply essential fatty acids but is usually adequate in practical rations. Water is an important nutrient and normally is provided with free access so it is not considered for ration formulation purposes. A palatable and economical energy source like corn or grain sorghum can be transformed into a nutritionally balanced ration if nutrient deficiencies are corrected.

Practical ration formulation must be sufficiently flexible to accommodate price and feedstuffs available while retaining the necessary nutritive balance and adequacy. When protein supplements are extremely expensive, it might be more economical to feed slightly less protein than recommended, even with a somewhat decreased rate of growth. Likewise, when protein supplements are cheap relative to grain, it is sometimes economical to supply a greater percentage of protein than is normally recommended.
Swine rations are usually formulated around cereal grains because they are low in fiber and high in energy. Corn is the most commonly fed grain; but, other grains such as sorghum grain, wheat or barley may be used. All grains are deficient in protein quantity and quality as well as minerals and vitamins. Corn is an excellent energy source, and soybean meal is an excellent amino acid source. Soybean meal can be fed as the only supplemental protein source for swine.

The nutrient content of grains is affected by factors such as type or cultivar, stage of maturity at harvest, soil and climatic conditions, location grown, and time in storage. Nutrient requirements of animals vary due to age, weight, sex, and function. Requirements may vary even in animals of the same weight. Therefore, rations are usually over-fortified as insurance against variations in feeds and requirements.
Usually high-energy, low-fiber rations are fed to swine, thus energy level is not a particular problem for growingfinishing animals. However, for gilt developer and gestation rations, lower energy and higher fiber levels can be used to control weight gains.

Logical Steps in Formulating a Ration
1.	Identify animals to be fed by age, weight, function and specific conditions under which they are fed. Penning and feeding in uniform lots allows a producer to more accurately meet the pigs’ requirement.
2.	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 Table 1 and are called nutrient allowances. Nutrient allowances may differ from requirements and may reflect special areas, regional needs, and even opinions. Table 2 gives some conversion factors that are very useful in ration calculations.
3.	Select suitable ingredients to help ensure that the ration is nutritionally balanced, palatable, safe, and economical. Some guidelines for utilizing different feeds are given in Table 3. Various feeding guides and example rations are helpful in selecting feed ingredients. Average analyses of selected ingredients are presented in Table 4.
4.	Determine the necessary fixed amount of certain ingredients (minerals and vitamins) and then mix grain(s) relative to protein supplement to provide the desired protein level. Rations can be formulated on either a cwt. basis or on a ton basis, depending on personal preference. The advantage of cwt. basis is that percentage figures for ration nutrients are the same as pound figures for ration nutrients. However, formulating rations on a ton basis can reduce calculations and time required, particularly where cost per ton of ration ingredients is to be determined. The

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. The Purdue University Cooperative Extension Service is an affirmative action/equal opportunity institution.