Tracking Sow Mortality

Producers, veterinarians and researchers are collecting and analyzing data to understand the causes of these losses.

By Tom Gillespie

In our industry, sow mortality has become a primary focus for producers, their veterinarians and diagnostic labs.

Only a short time ago, the mortality rates hovered around 5 percent in nearly all operations. In the past few years, however, the rates have escalated to unbelievable levels, often exceeding 10 percent for several weeks to months.

The elevated concern about sow mortality rates started three years ago, in a hallway at the annual meeting of the American Association of Swine Veterinarians, when a few veterinarians and pathologists began discussing what they saw in their practices. This humble beginning started us on the journey which led to an industry-wide study.

Originally, we focused on the unusual incidence of prolapses, often both rectal and uterine, in sows. We continue to explore this issue as a part of the overall research on sow mortality.

Drs. Bob Thompson and Kent Schwartz, along with Emily Mahan- Riggs, a student at North Carolina State University, compiled a survey and provided an “enrollment” sheet to any veterinarian willing to participate. These professionals filled out the surveys and submitted samples from problem sows.

To view similar data for your own farm, run the following PigCHAMP reports:
  • Performance trend analysis for periods up to 12/31/17 with period definition set to 12 calendar months and highlight observations that deviate.
  • Productivity analysis up to 12/31/17 for 12 calendar months.
  • Female removal analysis for 1/1/2017 to 12/31/17.
  • Reproductive loss report with services between 1/1/2017 to 12/31/17, with pages set to coordinate with your database.

You can quickly find several well-written papers on the subject of sow mortality. In 1991, Drs. Madeleine Chagnon, Sylvie D’Allaire and R. Drolet published the results of an extensive project which highlighted some interesting trends.1 They studied 24 breeding herds that submitted data on significant numbers of animals.

The herds had an average of 3,755 mated sows and gilts. The producers agreed to submit information on all dead and morbid sows over a 12-month period. During this window, the average sow mortality was 3.3 percent. The figures ranged broadly between operations, though, from the lowest mortality of 0.0 percent to the highest of 9.2.

In total, participating herds had a total of 137 sow mortalities. Researchers noted a higher mortality in the months of July, August and October. Sows appeared to be most at risk during the peripartum period that is immediately before, during and immediately after farrowing. During this short time in a sow’s reproductive life, 42.0 percent of all deaths occurred.

The three main reasons for death were heart failure (31.4 percent), torsions and accidents of abdominal organs (15.3 percent), and cystitis pyelonephritis (8.0 percent). Minor causes included endometritis, uterine prolapses, pneumonia and gastric ulcers.

Judging by a review of numerous papers, it seems that death rates had risen significantly by the mid- to late 1990s. In 1999, Drs. Christina Irwin, Jer Geiger, and John Deen presented at the North Carolina Healthy Hog Seminar that “today, 12 to 15 percent (or greater) sow mortality is seen with more and more frequency.”2

Interestingly, the researchers most frequently identified lameness (muscular-skeletal problems) as the cause of the animal’s demise (38.2 percent). The locations (either gestation or lactation) where the animal was housed immediately prior to euthanasia and or death varied, however.

The researchers identified gastro-intestinal problems as the second most common cause of death or euthanasia overall (12.9 percent). Again, location varied but was different than for lameness reasons.

Deaths by Parity

The authors later compiled a meta-analysis of 4 million parity records between 1996 and 1998, and they found some valuable insights. The researchers noted a significant increase in sow mortality within the systems examined. No system seems to have avoided this trend and the rates were significantly higher than reported in the literature.3, 4

In addition, some seasonality was apparent. The highest numbers of mortalities occurred in summer months, although there were differences between the systems. An interaction between season and stage of the reproductive cycle demonstrated that approximately half of the mortality occurred during the first three weeks after farrowing. In the summer, this number went up to roughly 65 percent.

Nevertheless, about 27 percent all mortalities occurred in sows that never farrowed. The authors speculated that an adverse event occurred prior to the subsequent periparturient risk (farrowing). They hypothesized that the stress of farrowing, i.e. loading into the crate, changing rations, act of delivery, etc. contributes to a higher risk of mortality during this critical time for the sow.

A more recent publication by Megan Schnur, DVM, Integrated Veterinary Network, shared further insights from another large database.5 The changes from gestation stalls to open pens have presented with some concerning levels of sow mortality. During the transition in the production system between 2006-12 and 2013-17, overall penned sow gestation space doubled (from 13 percent to 26 percent), Dr. Schnur says.

Mortality rates occurring in penned gestation farms, however, more than tripled, increasing from 7.9 percent to 27.7 percent. Euthanasia also increased as a reason of death, she noted. One can argue that, with PQA Plus standards in place throughout our industry, caretakers are being diligent in their daily activities. But Dr. Schnur’s findings raise questions about why euthanasia is needed more frequently now than in the past.

In our industry, many production systems of all sizes and individual farms are paying very close attention to this concern.

In their own ways, each of these systems and producers are developing tracking methods to capture reasons of death, location, parity and much more. This documentation is the result of a significant economic need to reduce mortalities and the emotional desire to make a difference.

Eventually, all of this data could be compiled and published, which could provide added incentive to the National Sow Mortality project. Dr. Chris Rademacher, a clinical associate professor at Iowa State University, says that the study is underway with 124 farms. Each of these producers compiles a weekly internal document with the goal of publishing the information soon on the Iowa Pork Industry Center website (ipic.iastate.edu).

An analysis of PigCHAMP’s 2017 benchmarking data also demonstrates an elevated sow mortality on most farms. (PigCHAMP’s database includes information from nearly 300 farms and close to half a million sows.) Sow mortality may not be a farm’s major economic concern but it is a matter that needs additional diagnostic help.

Nuber of Deaths

Mortality rates are rising in the late winter or early spring and peaking in April, the data shows. By losing parity 0 and parity 1 females, owners of swine units do not recover their investments. These losses are a drain on their profitability.

Taken together, the range of sources suggest that the risk factors associated with higher sow mortality are industry-wide.

To enhance our understanding of sow mortalities, researchers need to examine more sows to dive deeper into the contributing causes of death. These goals will necessitate a close working relationship between producers, diagnostic labs and pathologists – producers will need to submit more tissue samples to enable this research. The industry is tackling the problem of sow mortality, although it will take some time to fully understand and fix the issue.


  1. Chagnon, Madeleine, Sylvie D'Allaire and Drolet, R. “A prospective study of sow mortality in breeding herds.” Canadian Journal of Veterinary Research. 1991. 55: 180-4.
  2. Irwin, Christina, Jerome Geiger and John Deen. “Getting a handle on sow mortality.” Proceedings of the North Carolina Healthy Hogs Seminar. https://projects.ncsu.edu/project/swine_ extension/healthyhogs/book1999/irwin. htm
  3. Abiven, N et al. “Risk factors for high sow mortality in French swine herds.” Preventive Veterinary Medicine. 1998. 33 (1-4): 109-119.
  4. Christensen, G, L. Vraa-Andersen and J. Mousing. “Causes of mortality among sows in Danish pig herds.” Veterinary Record. 1995. 16: 395-399.
  5. nationalhogfarmer.com/animal-health/veterinarian-shares-observation-sow-mortality Feb. 15, 2018.

Tom Gillespie
Tom Gillespie has a lifelong involvement in the swine industry, beginning with his 4-H participation on his family’s hog and grain farm. He graduated from Purdue University with a doctor of veterinary medicine degree in 1979. In 1981, Gillespie moved to Indiana and joined as an owner in a mixed animal practice. He soon specialized in swine medicine. Gillespie obtained diplomate status with the American Board of Veterinary Practitioners in Swine Health and Management Specialty in 1989. He recertified in 2008 and again in 2017. Gillespie consults with swine operations worldwide.

He is the past president of the American Association of Swine Veterinarians (AASV). He was selected as the AASV Swine Practitioner of the Year in 2010. He has written several papers, including ones on pathogens.

Gillespie has lectured in most hog-producing states in the United States, as well as in Canada, Europe, Southeast Asia and China.

Tom Gillespie founded Rensselaer Swine Services, PC in 1991. Rensselaer Swine Services was obtained by Pipestone Veterinary Services in 2016.