Mortality Rates Inching Upward

The number of pigs dying around the globe appears to be on a slow but steady climb in the last decade. While the number of high-health herds being established is on the rise, the number of growing pigs dying is also on the rise, according to reports presented at the Leman Swine Conference, St. Paul, MN, in September. This seeming paradox appears to be due to shifts in production practices and disease

The number of pigs dying around the globe appears to be on a slow but steady climb in the last decade.

While the number of high-health herds being established is on the rise, the number of growing pigs dying is also on the rise, according to reports presented at the Leman Swine Conference, St. Paul, MN, in September.

This seeming paradox appears to be due to shifts in production practices and disease complexes, and not just to recent outbreaks of porcine circovirus-associated disease (PCVAD).

Production databases tell the story of this apparent contradiction, says Nashville, TN-based swine veterinarian Bill Christianson:

  • Agrimetrics Associates Inc. represented 15-20 large companies in the United States that comprise about 20-25% of U.S. sows. A 10-year trend of wean-to-finish mortality from 1996-2005 shows a slow but steady increase of less than 0.2%/year.

  • The National Animal Health Monitoring System (NAHMS) surveys production practices and disease levels of farm animals for the U.S. Department of Agriculture. In three swine surveys in 1990, 1995 and 2000, death loss of growing pigs averaged about 4.5 to 5%. NAHMS surveys smaller swine herds.

  • Wean-to-finish mortality in Danish herds during 1996-2005 suggests an increase of almost 2.5% (Figure 1). Christianson says this dataset is considered among the most reputable because of the way it is organized, and the controlled fashion in which industry results are reported. He says the upward trend in pig death loss began long before the ban on growth-promoting antibiotics in Denmark took effect a few years ago.

Those mortality rates are in line with the losses incurred in the United States. Losses in Denmark and across Europe the last 3-4 years reflect a more upward spiral due to greater losses associated with PCVAD, he adds.

Productivity Growth Overshadows Losses

Agrimetrics data reveals that despite the fact that more pigs are dying, overall sow productivity is increasing. Pounds produced/sow/year has gone from 4,600 in 1996 to more than 5,200 lb. in 2005 (Figure 2).

“This is the dilemma — sow production performance is booming, but yet, more pigs are dying. That is unacceptable to the public, and to producers as they continue to strive to make pig production more efficient and compete with other protein sources around the world,” explains Christianson.

“Throughput and efficiency are improving, yet more wean-to-finish pigs are dying today than ever before,” he adds.

Health Purchases Paradox

The other part of the paradox — an increase in health expenditures — is harder to pin down, says Christianson.

Data from Agrimetrics for the last 10 years (through 2005) shows that overall medication costs have remained relatively flat, but routine feed medication costs are becoming an increasing part of total medication cost/pig (Figure 3).

Large-scale production systems in the Midwest typically will average $2/finished pig in health costs, he says.

Causes for Increased Mortality

Christianson speculates there are a number of potential reasons for the pronounced growth in pig mortality:

  • Genetics has changed dramatically over the last 50 years. The proliferation of lean pigs and selection for production traits has been correlated over time with a decrease in livability.

  • Herd size has grown substantially in the last 15 years, allowing, on the positive side, for greater use of all-in, all-out pig flow. This has also led to the common use of multi-site production systems. But size of operations and pig flow dynamics may have negatively impacted overall herd immunity.

  • Disease issues are somewhat different today than 15 years ago. Around 1990, pseudorabies had not yet been eradicated in the United States and swine dysentery was still an issue. Today, pseudorabies has been eradicated in domestic swine and swine dysentery is much less of an issue.

Atrophic rhinitis, Actinobacillus pleuropneumonia, Transmissible gastroenteritis, mange and salmonellosis were major players in 1990. Many diseases in this group remain issues today, but are far better controlled.

Mycoplasmal pneumonia and porcine reproductive and respiratory syndrome (PRRS) were major problems then, and are arguably bigger problems today. Swine influenza virus was a known pathogen in 1990, but is a major issue today. Haemophilus parasuis causes more problems. PCVAD was unknown in 1990, but is increasingly frustrating to producers today.

“On the face of it, the disease situation is better today — we have better control systems — but we still have big looming issues out there,” says Christianson.

There may also be more non-infectious disease problems today, such as gastric ulcers and torsion, than were present earlier.

Addressing Health Issues

That's not to say that today's serious swine health concerns aren't correctable, he stresses. For instance, one operation that raises 400,000 pigs/year was virtually overwhelmed in 2001 with a variety of diseases, including PRRS, mycoplasma, influenza, Haemophilus parasuis and a variety of other common swine pathogens. Mortality rates were high and debates were common as to whether the owners could continue in pork production.

“However, they reduced their mortality back to acceptable levels, and they did it by management changes and vaccination programs,” says Christianson.

In short, they implemented early gilt development, developed sow farm vaccination programs to increase pig immunity downstream, increased weaning age, provided single-source flows of pigs to wean-to-finish facilities and improved timing of nursery vaccination.

Poultry Industry Progress

Christianson urged the swine veterinary community to emulate the great strides the poultry industry has achieved in reducing mortality while bettering performance.

In 1925, it took 112 days for a chicken to reach a market weight of 2.5 lb.; mortality was 18%. In 2005, average age at marketing was 44 days, weight was 5.25 lb. and mortality was just 4%.

He acknowledges that veterinarians are being bombarded with more information than ever before. Their challenge is to turn that information into knowledge by using discipline, tackling new disease problems head on and working on details in the production system that can be controlled to reduce pig mortality trends.

Diversity Defines Finishing Mortality

The days of simple answers to health challenges causing finishing mortalities are probably over, according to Matthew Turner, staff veterinarian for Prestage Farms Inc., Clinton, NC.

Preventing and treating a single bacterial or viral infection has given way to disease complexes that are far more challenging, he says.

A case in point is an outbreak of respiratory disease and mortality in a single flow of pigs that occurred at Prestage Farms in the fall of 2005.

Prestage Farms consists of 110,000 sows; 87% of the sows are in farrow-to-finish, three-site production systems, with the balance in farrow-to-feeder production.

Health of the sows and nurseries in 2005 was above average, says Turner. He described the quality of piglets placed into finishing sites as “average.”

At the time, three, 750-head, farrow-to-wean sow farms were undergoing depopulation to change genetics. All three groups were positive for porcine reproductive and respiratory syndrome (PRRS) and Mycoplasmal pneumonia, plus Pasteurella multocida Type A and Haemophilus parasuis.

Piglets were weaned at 14-24 days of age and commingled into all-in, all-out (AIAO) nursery rooms, then moved at 50-55 lb. into finishing barns managed AIAO by barn on a continuous-flow site.

In early 2005, periods of high mortality were sporadic with diarrhea as a key component, linked to salmonella and ileitis.

The pattern of mortality changed by the fall of 2005, to predictable high mortality caused by persistent respiratory challenge, including swine flu, porcine circovirus-associated disease (PCVAD), interstitial pneumonia and related lymphatic system problems.

Weight loss and death loss occurred from 14 to 18 weeks of age; survivors were near normal condition by 20 weeks of age.

During the outbreak, total mortality rates were 5% higher than normal, says Turner.

“The clinical presentation was unusual because the sow farms were in the process of depopulating. Generally speaking, the health status tends to improve as sow farms stabilize for multiple pathogens during depopulation; however, health in this flow diminished over time,” he explains.

Turner says the outbreak taught him several lessons:

  • Herd closure will not stop PCVAD;

  • Porcine circovirus Type 2 (PCV2) is not the only cause of high mortality in a herd, but it certainly can play a big role;

  • Diagnostic support is required to make an accurate diagnosis of PCVAD; and

  • It takes a lot of necropsy examinations to really know the health status of your herd when it comes to PCVAD.

Setting Finishing Mortality Targets

Determining what is an acceptable level of mortality in the finishing phase of production is a difficult task, says John Deen, DVM, associate professor at the University of Minnesota Swine Center.

“The problem is that unlike reproductive problems, where most of the challenges are noninfectious, mortality rates and morbidity rates are closely related to the disease status of the herd. Therefore, making a generalized benchmark across the industry (for growing pig mortality rates) just creates frustration,” Deen says.

When high-health, high-quality pigs flow to grow-finish, some systems regularly report 1½ to 2% mortality. “That can be used as a benchmark to aim for if system-level factors are under control. Similar levels can be reached in the nursery,” he notes.

A second problem with benchmarking mortality is that the process should also cover morbidity, usually measured as cull and lightweight pigs.

Deen stresses producers shouldn't cull pigs that need to be euthanized just to minimize mortality rates. These marginal pigs are usually shipped to a secondary market that accepts poor pigs, and thus, are excluded from mortality rates.

Disease control practices are another concern. The challenge is to not only lower mortality rates, but also lower morbidity or symptoms of disease in pigs, he adds.