United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

Veterinary Services 

Centers for Epidemiology and Animal Health December 2008 

_________________________________________________________________________________________________________________________ 

Highlights of Swine 2006 Part IV: 

Changes in the U.S. Pork 

Industry, 1990-2006 

In 2006, the National Animal Health Monitoring 

System (NAHMS) conducted a study of U.S. swine 

operations. The Swine 2006 study collected data 

on swine health and management practices from 

17 of the Nation’s major swine States.*

 These 

States represented 94 percent of U.S. swine 

operations and inventory on operations with 100 or 

more pigs. 

 The following highlights were excerpted from 

the report released in December 2008: “Swine 

2006 Part IV: Changes in the U.S. Pork Industry, 

1990-2006”. Part IV identifies trends in the U.S. 

swine industry and specifically addresses changes 

identified from four NAHMS swine studies: the 1990 

National Swine Survey, Swine ’95, Swine 2000, 

and Swine 2006. 

Demographic changes 

• U.S. hog and pig inventory peaked in 1959 at 

nearly 68 million head. The number of hog sites 

declined dramatically starting in 1959. 

Estimates in subsequent years consistently 

remained near 55 million head, increasing to 

60.4 million head in 2002. The 2002 Census of 

Agriculture showed the number of swine sites at 

only 1.8 percent of those in 1900, while the 

inventory number of head was nearly the same. 

As a result, the average herd size increased 

from fewer than 20 head in the early and mid 

1900s to 766 head in 2002. 

• The number of U.S. swine sites has decreased 

steadily since 1990. In 2000, the number of 

swine sites in the United States had decreased 

by two-thirds of the 1990 number, and in 2006 

the number of swine sites was fewer than onefourth the number reported in 1990. 

 

*

 Arkansas, Colorado, Illinois, Indiana, Iowa, Kansas, Michigan, 

Minnesota, Missouri, Nebraska, North Carolina, Ohio, Oklahoma, 

Pennsylvania, South Dakota, Texas, Wisconsin.

• December 1, 2006, inventory levels were 

considerably above December 1, 1990, levels, 

especially in the three States with the most 

pigs—Iowa, North Carolina, and Minnesota—as 

well as many of the Western States. Declining 

inventories were shown in the traditional hograising States of Illinois, Indiana, Ohio, South 

Dakota, and Wisconsin. 

Health and productivity changes 

• Since 1990, the number of pigs born alive per 

litter has increased by 1.33 piglets per litter, and 

total born per litter has increased by 1.50 

piglets per litter. The number of pigs weaned 

per litter increased by about one pig per litter 

from 1990 to 2006. 

• Stillbirths and mummies as a percentage of 

total born per litter increased steadily from 1995 

to 2006. In all four NAHMS swine studies, 

producers identified piglets lain on as the 

leading cause of preweaning deaths. 

• In breeding herds, the percentage of operations 

in which PRRS was diagnosed by a 

veterinarian or a laboratory was unchanged 

from 2000 to 2006, and PRRS was the most 

prevalent of the listed diseases diagnosed by a 

veterinarian or laboratory during the previous 

12 months (table 1). 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

Table 1. Percentage of Sites in Which the Following 

Diseases were Diagnosed in the Breeding Herd by a 

Veterinarian or Laboratory During the Previous 12 

Months

 Percent Sites 

Disease Swine 2000 Swine 2006 

PRRS 16.2 18.8 

APP 1.5 3.2 

Mycoplasma

pneumonia 7.3 8.8 

Roundworms 7.0 2.6 

Traditional 

swine flu (H1N1) 6.8 5.6 

Gastric ulcers 4.7 9.3 

New swine 

flu (H3N2) 4.5 4.8 

Glasser’s disease 3.0 1.8 

Parvovirus 2.3 3.8 

Erysipelas 1.9 3.9 

Management changes 

• The percentage of sites that used artificial 

insemination as the predominant mating 

technique in sows and gilts increased from 

2000 (24.3 and 28.7 percent, respectively) to 

2006 (40.1 and 41.8 percent, respectively). 

• The percentage of sites that used continuous 

flow management in the grower/finisher phase 

decreased steadily from 75.1 percent of sites in 

1990 to 26.1 percent in 2006. 

• Regular use of influenza vaccines more than 

doubled in breeding females between 2000 and 

2006 (table 2). 

Table 2. Percentage of Sites with the Following 

Production Phases During the 12 Months Prior to the 

Survey1

 that Usually Vaccinated Within the 

Production Phases Against the Listed Diseases 

Breeding 

Females 

Weaned 

Pigs2

Disease 

Swine 

2000 

Swine 

2006 

Swine 

2000 

Swine 

2006 

Mycoplasma

pneumonia 20.9 34.9 40.0 35.6 

PRRS 37.1 27.3 5.2 5.4 

Swine 

influenza H1N1 11.2 27.9 4.8 9.5 

Swine 

influenza H3N2 10.6 27.8 5.0 8.7 1

August 21-October 31, 1999, and September 5, 2005-March 15, 2006.

2

Weaned pigs are those in a nursery or grower/finisher stage. 

________________________________ 

For more information, contact: 

USDA:APHIS:VS:CEAH 

NRRC Building B, M.S. 2E7 

2150 Centre Avenue 

Fort Collins, CO 80526-8117 

970.494.7000 

E-mail: NAHMS@aphis.usda.gov 

http://nahms.aphis.usda.gov 

#N539.1208 

____________________________________ 

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