NUTRITION
PIH-71
pork industry handbook
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA
Physical Forms of Feed—Feed Processing for Swine
Authors
Maynard Hogberg, Michigan State University
Don Mahan, Ohio State University and OARDC
Robert Seerley, University of Georgia
Reviewers
Keith Behnke, Kansas State University
Roger Haugen, North Dakota State University
Dean Zimmerman, Iowa State University
Approximately 65-70% of the total cost of producing a market hog can be attributed to feed. As such, it is desirable for the swine producer to find the most economical feeding method to achieve the lowest cost per unit gain.

Feeding and processing methods should be evaluated both individually and collectively as to their potential to improve the economics of swine production. Nutrient availability and balance are important in diet formulation and are dependent not only on the feedstuff but may be altered by processing methods. Diets based strictly on least-cost formulations do not always result in the lowest cost of production. Consequently, this fact sheet deals with feedstuff ingredients, specific nutrient limitations and the physical forms of these feedstuffs. All are essential to maximizing profits in the hog industry.

Why study feeds?
Producers must understand the various processing techniques and associated feeding problems to make a system usable for their operation. For example, feedstuffs may be more acceptable to the pig in one physical form than another, thus improving feed intake. The digestibility of the nutrients within each feedstuff may be improved if the surface area is increased to allow greater exposure to digestive enzymatic activity, thus enhancing nutrient availability; but in other cases, altered feed surface areas may reduce diet acceptance. Processing could lower the availability of nutrients in grains, such as the destruction of vitamins; but in other cases, it could increase their use by the pig. Although a laboratory-conducted nutrient analysis of a feedstuff may not be changed, the digestibility and availability of nutrients may be enhanced or hindered by various processing methods. Thus, nutrient analyses coupled with an understanding of the effects of feed-processing are essential to insure optimum performance.
Free-Choice vs. Complete Feeds
In free-choice feeding, different components of the diet, such as grain and supplemental protein fortified with vitamins and minerals, are provided in separate compartments of a self-feeder. This compartmentalization allows the pig to eat as much of each component as desired. Thus the pig makes the choice in balancing the diet.

While free-choice feeding offers the greater simplicity for swine producers, more supervision is usually required to insure an adequate intake of all nutrients and optimum performance. Overeating or undereating of the protein-mineral-vitamin supplement may occur if the grain or supplement varies in acceptability to the pig. Generally, when feedstuffs are of poor quality (e.g., molds, extreme dryness, etc.), a depression in intake is observed and a corresponding increase in the consumption of the other components results. Maintaining quality is more important with grain as grain varies more in quality than most processed supplement sources. Supplement intake can sometimes be controlled, however, by keeping the number of feeder holes containing the supplement low, but adequate, relative to those containing grain.

The free-choice system usually produces a slower rate of gain than feeding a completely mixed diet, especially with younger pigs to 100 lbs. bodyweight. If free-choice feeding is not properly monitored, poor feed efficiency can easily occur.

Complete mixed feeds or those with the proper balance of nutrients mixed and supplied in one batch are the most common methods of feeding swine. Complete mixed swine feeds are generally more satisfactory for most swine operations.

Limit-fed gestating sows will perform equally well when fed their diet components (grain and supplement) separately or as a completely mixed feed. It is advisable to feed
Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U. S. Department of Agriculture Cooperating. H. G. Diesslin, Director, West Lafayette, Ind. 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, religion, color, sex or national origin.