Science Page: PRRS incidence in status 4 sow farms

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week,  we are sharing a report by the MSHMP team on PRRS incidence in status 4 sow farms.

Key points

  • In the last 9 years, on average 10.2% (Range 3.7% – 22%) of status 4 farms have had a PRRS outbreak during the MSHMP season and in the 2017-2018 season, the cumulative incidence (July to April) is 9.6%.
  • The lowest PRRS incidence was observed during the 2013/2014 PRRS season; the year that PED entered the US.
  • PRRS incidence in status 4 farms during the current MSHMP season is not higher than the ones observed in the previous MSHMP seasons.

Reminder: Status 4 sow farms are the farms that considered negative both in shedding and exposure status in the classification document published by the AASV.


Has there been an increase in PRRS outbreaks incidence in status 4 sow farms?


PRRS incidence in status 4 farms from 2009 to April 2018 was compiled and compared with the current MSHMP year using Fisher’s Exact test.


During the current MSHMP year (July 2017- April 2018), 27 status 4 farms have had a PRRS outbreak (6.9% incidence). The average incidence of status 4 farms from 2009 to April 2018 was 9.6%. However, PRRS incidence have varied greatly among years (figure 1). PRRS incidence had its minimum value during the 2013/2014 MSHMP season with a 3.4%. This coincides with the year that porcine epidemic diarrhea virus (PEDv) entered the US.

When comparing the incidence during the 2017/2018 MSHMP year with the incidence observed during the 2015/2016 MSHMP year, a borderline significant difference (p=0.06) was observed.

PRRS incidence in status 4 sow farms
Figure 1. Percentage of PRRS incidence in Status 4 farms by year (July-April)


PRRS incidence in status 4 farms (July 2017 –April 2018) was overall similar to previous years, although slightly higher than July 2016-April 2017, and significantly lower than July 2015-April 2016. Other factors, such as region, may be contributing to the
perception of increased PRRS incidence in status 4 farms.Exploring these factors may help explain the perception of increased

Best of Leman 2017 series #5: J. Pittman – We’ve posted a lot of sows.

We launched a new series on the blog in October. Once a month, we are sharing with you a presentation given at the 2017 Allen D. Leman swine conference, on topics that the swine group found interesting, innovative or that lead to great discussions.

The fifth presentation we are sharing is from Dr. Jeremy Pittman from Smithfield’s, NC. In the context of increased sow mortality, Dr. Pittman spent a lot of time investigating the root causes of this change and he shares his experience in this talk.

To listen to this talk, please click on the picture below.

Pittman posted a lot of sows.gif

Science Page: Describing the cull sow and cull hog market networks in the US: A pilot project

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week, we are sharing a project from Dr. Jim Lowe at the University of Illinois.

Project rationale

“What is the range of locations of sows that enter a slaughter plant?, How many stops along the way do they make? and How long do they remain the slaughter channel?” These are the questions this project is planning to answer.

Key Points:

  • Little is known about the cull market, how culls are transported, and how they play a role in disease spread.
  • While most sows travel directly to slaughter, an important percentage most likely move through multiple collection points.
  • Cull sow movement are important for understanding disease transport related epidemiology.

Premise ID tags were collected during an entire week at a cull harvest plant. Animals originated from 297 unique source farms, located in 21 US states and Canada.

distance from farm to marketResults are shown in the histogram on the left.

The majority of culls (86%) originate less than 240km from the final collection point. This interaction is deemed to be a primary interaction, meaning that it is very likely the culls moved direct from the farm of origin to the final collection point. 14% of the culls travel a distance greater than 240km to the terminal collection point. Of these 14%, 17.7% or 2.5% of all culls, traveled 5 times as far to the last point of collection from the farm than they did from collection point to plant.

Click here to see the entire report on the cull sows and cull hogs market.

How much floor space does a pregnant sow need in a group-housing system with electronic sow feeders?

Sows housed in groups at the UMN facility in Morris

The University of Minnesota – Morris owns a swine research facility which provides an excellent set up to study the behavior of sows housed in groups. In the past few years, swine producers have committed to change the conditions in which the sows are housed in farms and to keep them in groups where they can interact with each other instead of housing them individually. Putting sows in group reminded us that pigs need a hierarchy and that they will compete and fight to establish it. Because space allowance can impact sows behavior we wondered what the optimum floor space is.

Read the entire report on floor space allowance for sows by Dr. Yuzhi Li

Determining floor space allowance for gestating sows can be controversial because more floor space allowance means low output per square footage of the barn and will potentially reduce profitability for producers. On the other hand, floor space allowance less than sow requirement can compromise sow welfare and performance. To answer the question in the title of this article, we conducted a two-year project (titled ‘Determining the Minimal Floor Space Allowance for Gestating Sows Kept in Pens with Electronic Sow Feeders’). The project was partially sponsored by the National Pork Board, and the research team includes Yuzhi Li and Lee Johnston from the WCROC in Morris, and Sam Baidoo from the SCROC (Southern Research and Outreach Center) in Waseca.[…]