The newly released National Animal Health Monitoring System (NAHMS) report on swine health and management shows 39.1% of hogs that die in the finisher phase succumb to respiratory diseases.

Finisher deaths from respiratory disease accounted for 47.9% of deaths in 1990, then dropped to 40.2% in 1995, according to previous NAHMS reports.

In the nursery, 23.9% of deaths were caused by respiratory problems in 1990, 32.4% in 1995 and 28.9% in 2000. Table 1 and Figure 1 show cause of death in farrowing, nursery and finishing phases of production.

The 2000 NAHMS report is the third national study undertaken on the swine industry. The first, in 1990, focused primarily on farrowing, sows and preweaning piglets. The 1995 report focused primarily on the grow/finish stage of production.

The 2000 report provides survey information on 94% of the U.S. swine herd. Data were collected from 2,499 swine production sites from 2,328 operations in 17 major pork-producing states. The data in the first portion of the report were collected by National Agriculture Statistics Service personnel between June 1 and July 14, 2000.

NAHMS will continue to release data collected by state and federal veterinary medical officers and animal health technicians from Aug. 21 to Nov. 3, 2000 and from Dec. 1, 2000 to Feb. 28, 2001.

The second reference report will be released in December and will focus on vaccination for respiratory disease.

For more information on NAHMS studies and reports, go to

Trends Identified

Eric Bush, DVM, veterinary epidemiologist for USDA's Centers for Epidemiology and Animal Health in Fort Collins, CO, identified several key trends in the data, including:

  • More producers are isolating new breeding stock.

    “The trend is a greater adoption of this practice for both breeding females and males,” he says.

    The percentage of sites isolating breeding females increased from 55.7% in 1990 to 60% in 1995 and stood at 70.3% in 2000.

    For breeding males, 68% were isolated in 1990, 75.2% in 1995 and 76.6% in 2000.

    The number of days in isolation also increased.

    “For breeding females, isolation averages 38.7 days, compared to 30.8 days in 1990,” he says. “For breeding males, it averages 34.3 days, compared to 28.7 days in 1990.”

    The use of isolation is more likely at larger sow farms than smaller sites. On large farms (500 or more sows), 68.9% always isolate new breeding females.

    New breeding females are isolated 57% of the time on medium-sized farms (250 to 500 sows), and 25.9% of small farms (250 or fewer sows) always isolate new breeding females. It is important to note that 48.5% of small farms were closed herds.

    The upward trend should help producers in their efforts to control respiratory and other infectious diseases, Bush adds.

  • More production sites are health testing new breeding animals.

    “As with isolation, the trend in health testing of new breeding females and males is toward greater use of this tool,” Bush says.

    For farms bringing in new gilts, the percent conducting health testing was 42.1% in 1990, 52.7% in 1995 and 60.3% in 2000. Farms that brought in new boars tested 49.3% of them in 1990, 56.1% in 1995 and 60.1% in 2000.

    “Instead of relying solely on the development of noticeable sickness, testing applies a more objective and powerful observation tool to detect disease in new arrivals before introduction,” he says.

    “A great example is porcine reproductive and respiratory syndrome (PRRS). Boars can shed PRRS virus in their semen as long as 60 days. This would not be detected in new boars except for conducting PRRS testing,” Bush adds.

    On large farms, 37.1% of farms test all new gilts. On medium farms, 45.7% test all the new gilts and 44.6% of small farms do so.

    For large farms bringing in new boars, 61.6% were tested. Medium-sized farms tested 56% of new boars and small farms tested 50.2%.

    Bush notes that larger farms may test a sample of new animals, as they are received in larger groups, while smaller farms may test each individual animal.

  • All-in, all-out (AIAO) management continues to grow in popularity.

    “Emptying out the whole airspace and thoroughly cleaning and disinfecting the facilities during the idle time prevents the continual spread of respiratory diseases,” Bush explains. “AIAO provides a disease firewall.”

    Less than 11.1% of market hogs begin in continuous-flow (non-AIAO) nurseries and 14.9% are raised in continuous-flow grow/finish units.

    In 1995, 30.2% of pigs entered a continuous-flow nursery and 49% of grow/finish hogs were housed in continuous-flow facilities.

The 2000 report shows the following for nursery management:

  • 24.4% of nurseries are AIAO by room;

  • 32.3% of nurseries are AIAO by building;

  • 3.5% are AIAO by site;

  • 32.3% are continuous flow, and

  • 3.9% are AIAO, but not cleaned or disinfected between groups.

For the grow/finish phase:

  • 10.7% are AIAO by room;

  • 32.3% are AIAO by building;

  • 10.7% are AIAO by site;

  • 40.5% are continuous flow, and

  • 3.2% are AIAO, but not cleaned or disinfected between groups.


In addition to isolating and acclimating new breeding stock, producers vaccinated new breeding animals. On large farms, 89.3% of animals were vaccinated, compared to 91.8% on medium-sized farms and 81.6% of animals on small farms.

Overall, about 75% of sites routinely administered one or more vaccines against common swine diseases.

Mycoplasma vaccine was the most frequently used at large and medium-sized farms. At medium-sized finishing sites (2,000 to 9,999 head), 59.1% of hogs are vaccinated, while 62.9% of hogs at large sites (10,000 or more head) were vaccinated for Mycoplasmal pneumonia. In all, 37.5% of all farms vaccinated for the disease.

PRRS vaccination is a part of herd health programs on 28.3% of farms. Broken down, that accounts for 27.3% of small farms, 33.5% of medium-sized farms and 31.7% of large farms.

A total of 11.1% of farms vaccinated for the traditional H1N1 swine influenza virus (SIV) and 9.6% vaccinated for the new H3N2 SIV. Bush noted that the use of SIV vaccine was underestimated in the survey because some producers did not know which specific type of vaccine was used.

Thirty-five percent of farms vaccinate for rhinitis (pasteurella, bordetella), including 37.5% of small farms, 25% of medium-sized farms and 13.9% of large farms.

Table 1. Deaths from Respiratory Problems

Time Period (by percent)
Phase of Production Dec. 1999-Feb. 2000 March 2000-May 2000 Dec. 1999-May 2000
Preweaning 3.1 2.8 3.0
Nursery 28.9 28.6 28.9
Grower/Finisher N/A N/A 39.1