To the Editor

May and June, 1999

[Responses to this proposal appear in the September and October, 1999 issue.]

Proposed standardized nomenclature and an alphanumeric notation system

Dear Editor:

Swine veterinarians, producers, lenders, and others associated with the swine industry use a variety of terms to describe multisite production systems. In the interests of improved communications in this important area of swine production, we suggest that the following terms, definitions, and alphanumeric notation be adopted as a standard nomenclature1 for Swine Health and Production.

Stages of production2

We propose that the three stages of production be referred to as:

  • Breeding production stage (stage one): The production stage in which breeding females and boars are kept and managed for the purpose of producing weaned pigs;
  • Nursery production stage (stage two): The production stage associated with nursery pigs; and
  • Finisher production stage (stage three): The production stage associated with finisher pigs.


A site number indicates the placement for the various stages of production. Pigs may be reared on one or more locations (loci) within a site.

Locus or loci

Loci indicate the number of geographic locations for each stage of production at each site. There may be one or more buildings at each locus. In referring to source(s) of pigs, the word source may be substituted for locus or loci in reference to either originating from site one or two.


At weaning, piglets are placed in isolated accommodations. The purpose of Isowean is twofold:

  • to eliminate infectious agents, and
  • to enhance growth rate and lean tissue deposition.

Precautions are taken to assure that each group of Isowean pigs are not contaminated by other age groups of pigs. The weaning age is variable from 5 days up to 21-28 days of age depending upon the infectious agents to be eliminated.

Other terms that have been used as synonyms for Isowean are:

  • modified medicated early weaning (MMEW),
  • segregated early weaning (SEW),4
  • segregated weaning,
  • age-segregated rearing (ASR),
  • isolated weaning, and
  • segregated disease control (SDC).

We recommend that the synonymous terms not be used.

Types of production systems

  • One-site (farrow-to-finish): All three stages of production take place on site one in one locus. Historically, the traditional way pigs were raised.
  • Traditional two-site: Two-site production when stages one and two are placed on site one (at one or more loci) and stage three is placed on site two (at one or more loci). Prior to 1989, this was the only type of two-site production system.
  • Two-site Isowean: Two-site production when stage one is place on site one (at one or more loci) and both stages two and three are placed on site two (at one or more loci). Isowean is applied between sites one and two.
  • Three-site: Each of the three stages of production are located on three separate sites; referred to as sites one, two, and three respectively. Each stage of production may be on one or more loci within a site. Isowean is applied between sites one and two.

Multi-sources and multi-loci

The breeding production stage in traditional two-site, two-site Isowean, and three-site herds may be on more than one loci within site one. In addition, these systems may place pigs in the nursery and finisher production stages on more than one locus within sites two and three. Therefore, these terms are used to indicate whether pigs originate from either single or multisources in site one and if either single or multiloci are used in sites two and three. Examples are: two-site Isowean (single source, multiloci) and three-site (multisource, single locus).

In the past, the term "multiple site production" has been used to refer to a three-site (multisource, multiloci) system. We recommend that the term "multiple site production" not be used because it does not clearly distinguish between multisources and/or multiloci.

Multisite pig production

A blanket term to cover any arrangement of sites and loci including all types of two- and three-site production systems. Isowean may or may not be applied.

Multisite Isowean production

A blanket term to cover any arrangement of sites that incorporates the Isowean including the various possible configurations for two- and three-site production. Isowean pigs may be from single or multiple sources. Also referred to as modern multisite production.

Alphanumeric notation

Letters and numerals can be assigned to the various terms used in describing both one-site and multisite production systems. Thus, an alphanumeric notation system has been devised to indicate the layout, design, and nature of the pig throughput of a swine rearing system. By the use of a simple key that denotes letters for words and numerals for arithmetic designators, a database-friendly system can readily be devised. An example of a three-site (single source, single locus) farm is:

S1=SP1,L1; S2=SP2,L1; S3=SP3,L1

where S=site, SP=stage of production, and L= locus.

This is a very simplified version of the alphanumeric notation system. The notation can be made more detailed by including the number of buildings (B) per locus, the number of pigs (NP) per building or room (R) or locus and so forth. As suggested by Steve Henry, global positioning satellites (GPS) coordinates can be used to indicate the exact location of buildings and/or loci.

--Drs. D.L. Hank Harris and Isabel T. Harris
Iowa State University


1. For a more complete explanation of terms, definitions, alphanumeric notation, and diagrams see the following publications:

  • Harris DL. Multi-Site Pig Production. Ames, Iowa: Iowa State University Press, 1999(in press)
  • Harris DL, Alexander TJL. Methods of Disease Control. in Straw B, et al. Eds, 8th ed., Diseases of Swine. Ames, Iowa: Iowa State University Press; 1999.

For examples of diagrams in color and additional terms see: Harris DL, Harris IT. Swine Practitioner, March/April 1999; pp. 4-8.

2. Terms recommended by Will Marsh, editor, National Pork Production and Financial Technical Manual, Des Moines, Iowa: National Pork Producers Council; 1998.

3. Harris DL. Large An Vet. 1990; 10-12. Harris DL. Proc IPVS Cong. 1990; 374.

The term Isowean was initially registered as a trademark by PIC. Recently, PIC has released this trademark term (Isowean) for use by the general public. Isowean is preferred over MMEW and SEW because early weaning is not required for the benefits of isolated weaning to be realized.

4. Goodwin RN, Burroughs S. 1995. NPPC Terminal Sire Line National Genetic Evaluation Results. Des Moines, IA. The NPPC created the term "SEW" because of the original trademark restrictions on the use of the word Isowean.

Editor's note: We wish to encourage readers to respond to the proposal to adopt standard nomenclature. Responses can be sent Drs. Harris and Harris, or to the editorial staff of SHAP (