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Articles from 2007 In April

Debating Meat Dominance

Debating Meat Dominance

So what is the "dominant" meat in the U.S. marketplace? That probably depends on how you want to define dominant. Perspective is such an important issue in so many things, isn't it?

In terms of per capita disappearance/consumption on a boneless equivalent basis, beef still maintains a narrow lead over chicken in the United States (See Figure 1). That lead actually grew slightly in 2006, and is forecast by the Livestock Marketing Information Center in Denver to remain the same in 2007.

The trend for beef is flat while the trend for retail weight chicken production, though it declined last year and may do so this year, is still up. Note that retail weight pork consumption has changed little for the past 20 years, meaning that pork industry growth has been completely dependent upon population growth and exports.

Boneless equivalent is probably our best measure of what people actually eat since it leaves out much of the "waste" that we see in meat products. The figure is still based on the residual of production plus imports plus inventory change over the amount we export, since no ongoing public data exists that reflects direct measurement of consumption. In addition, this figure (and retail weight, for that matter) is based on rather old factors that convert carcass weight production to downstream weights based on standard cutting methods, trim loss, pet food usage, etc. The U.S. Department of Agriculture is presently revising those conversion factors.

Chicken Wins on Volume Purchased
If we measure importance in terms of the volume of product that people actually purchase (See Figure 2), chicken is the clear winner with per capita retail weight consumption over 20 lb. higher than beef and nearly 30 lb. higher than pork. The same trends are evident here that are evident in the boneless equivalent chart since they are related by a constant conversion factor.

The argument can clearly be made that either of these "consumption" measures is really just a matter of production since "consumption" here is just what is left over after we deduct the things we actually measure (imports, exports and frozen stocks). And year-to-year variation in "consumption" is indeed a matter of production variation. The kicker, of course, is what price a given level of production/disappearance/consumption results in and the concurrent value of total disappearance/consumption.

Beef Rules Expenditures
Figure 3 shows total retail level expenditures (price times quantity) for the four major species through 2006. By this measure, beef is still the "ten ton gorilla" of the meat sector. Pork maintained a narrow lead over chicken for many years before chicken took over second place in 2004. Pork expenditures moved back ahead of chicken in 2006 as chicken prices fell dramatically and pork prices declined by a smaller amount.

The Case for Chicken
While important, none of these charts provides a complete answer about which is the "dominant" meat if, in fact, there is one. Len Steiner of Steiner Consulting Group makes a compelling argument that chicken has become the leader of the meat business. Its huge presence in virtually every level of foodservice usage and its many product forms in retail stores make it ubiquitous. In addition, its position as the lowest-cost meat protein always makes it a good option for tight budgets and the ability of the industry to respond quickly to prices (such as is the case at present), and price pain leaves it in a terrific position to capitalize on opportunities and, with some discipline, limit the duration of losses.

Experiences with Price Pain
The industry has not historically responded very well to price pain, at least partially because it doesn't have much painful price experience. The merger of Tyson and IBP, however, has brought a degree of red meat margin management to the chicken industry, and probably means that the industry will respond more quickly to low prices than it has in the past. When your business always grows by 4%/year, market share is a pretty simple way to measure success. Slower growth, though, amplifies the importance of margins and will likely result in more response to them. Last year is one instance of chicken's new-found margin sensitivity, and this year may be the first measure of its responsiveness to regained margins.

Click to view graphs.

Steve R. Meyer, Ph.D.
Paragon Economics, Inc.

The Risks of Misdiagnosis

The first step in dealing with any herd health challenge is diagnosing the problem. Without this critical step, launching into therapeutic or preventative responses is foolhardy and the chances of success will be severely limited.

But what happens when the initial diagnosis is wrong?

A misguided diagnosis could happen any number of ways:

  • The presenting clinical signs might be confusing or misleading to the untrained eye;

  • The presenting problem may be just one part of a disease complex;

  • There may be several disease processes occurring within the population at the same time, and only one (perhaps the most innocuous) rises to the degree of clinical disease;

  • The experience of the person making the diagnosis may be too limited when a “new” or different disease process occurs;

  • The problem may be over-simplified;

  • The diagnosis could be based on faulty information; or

  • Lab tests are either not specific or sensitive enough for a particular disease.

No Simple Answers

The days of simple answers to challenging health problems, making a “drive-by diagnosis” or expecting an accurate diagnosis over the phone are gone forever. Even a veterinarian with a lifetime of experience diagnosing diseases will submit lab samples to confirm or deny their preliminary diagnosis.

Recently, I participated in a large mortality surveillance study that involved performing necropsies (postmortem exams) on a large number of grow-finish animals. The pigs were necropsied and the findings were compared to the “barn” diagnosis.

The barn diagnosis is typically made by the caretakers and is based on the outward appearance of the carcass and where it was found within the barn. As is commonly done, the caretakers were instructed to choose the diagnosis from an abbreviated list of mortality reasons, which for the most part was outdated and incomplete.

The results of this survey were quite disturbing. Of more than 1,000 pigs that were necropsied, the barn diagnosis was correct on only 40% of the cases.

The technicians who performed the necropsies checked their accuracy by submitting tissues to a state diagnostic laboratory. Results showed they were nearly 100% correct in their determination of reasons for death based on gross lesions.

The lesson learned from this survey was that “eyeballing” carcasses and “educated guessing” should be avoided.

What is the most concerning about the outcome of this study was that we had been making significant herd health-related decisions based on severely flawed information.

In response to the monthly death loss summaries, vaccination protocols and antibiotic therapy were instituted, but they were doomed to fail because they were attempting to attack the wrong enemy!

Why Are These Pigs Dying?

Finishing pig health has been defined many different ways, but often the first noticeable sign of problems in the finishing phase of production is a rise in the mortality rate.

Across the industry, mortality rates vary widely between systems and even between sites or groups of pigs within a system.

Two decades ago, it was uncommon for a producer to report more than 3% mortality in finishing; 1-2% was the target.

When mortality occurs, eventually someone asks: “Why?”

Perhaps the question doesn't come with the first few mortalities, but when the death rate for the group exceeds the interference level for that particular group or system, it is imperative that we try to understand what is going on.

Morbidity is the term used to describe the illness rate or the frequency of animals in the population that are sick. Mortality rate describes the number of deaths that occur in a given group or from a given cause.

You may hear veterinarians refer to a disease as having high morbidity, but low mortality. This means that many in the group got sick, but few died from the disease. This would describe how Mycoplasmal pneumonia.

On the other hand, a syndrome such as hemorrhagic bowel syndrome (HBS) may affect only a few pigs in the population (low morbidity), but it kills nearly every pig it affects (high mortality).

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Steps to an Effective Diagnosis

Veterinarians and physicians have been trained to use a systematic, stepwise approach to making a diagnosis when confronted with a health issue or problem.

Step 1: Gather the History

The first step is to gather a thorough history of the patient, or in this case, a group of pigs. This generally requires asking a lot of questions. Here are some examples that may be asked about a group of feeder pigs (in no particular order):

Where did the pigs originate?

When did the pigs arrive?

What was the health status of the source herd?

Have there been problems with pigs from this source before?

What was the nature of the problems?

Were the problems resolved?

Is the current problem similar to past health issues?

Are there predictable spikes or peaks of mortality?

What did these pigs weigh when they arrived?

Are they gilts, barrows or mixed sex?

Were they vaccinated? With what?

Have they been treated? With what?

Was the treatment successful?

How many are or have been sick?

How many have died?

Have there been any issues with ventilation? Temperature? Feed? Water?

Are the pigs eating? Drinking?

What has been the feed disappearance rate and water usage for the site?

What feed ration is being offered?

Is the feed medicated? With what?

Who is the caretaker? Experience level?

Have any diagnostic tests or post-mortem exams been done?

Do production records indicate a level of performance that is within industry standards?

What biosecurity protocols are in place? Are they enforced?

Step 2: Physical Examination

The next step towards making a diagnosis is to physically examine the pigs and their environment. This step occasionally requires the use of all of your senses: sight, sound, smell, touch and at times, taste. A sixth sense — “pig sense” — may also prove valuable for the physical exam.

The physical exam in pig barns may also be called a “barn walk.” You must observe the pigs' behavior; assess their environment, feed and water availability; and check for the presence of clinical symptoms, such as coughing, thumping, diarrhea, lameness or other physical or medical condition that would indicate a problem.

While you are examining the population, you must focus on individuals and assess every pig for clues as to the problem or problems affecting the population.

It is very important to “listen” to the pigs. In this case, listening is more than using your ears. It also includes carefully observing behavior, appearance, condition and activity levels. The pigs will “tell” you what is bothering them. The better “listener” you become, the fewer misdiagnoses or mistakes you will make.

The physical exam is the subjective step in the diagnostic process, and thus will force you to draw on your experience and impressions of how normal pigs should look and act. This is where “pig sense” is so invaluable. You must know and understand “normal” behavior and appearance before you can make an initial clinical diagnosis of “abnormal” or “sick.”

The best caregivers perform a physical exam every day. The only difference is they tend to call the process “chores.” Swine veterinarians know that good chores are dependent on the ability of the caregiver to observe pigs carefully and know the difference between normal and abnormal behaviors. Good chores generally lead to good health and performance.

Necropsy is a valuable and necessary tool that should be used as part of the physical exam. An experienced necropsy technician can differentiate normal organ systems from diseased systems, which allows the search for a diagnosis to become more focused.

Necropsy should be performed on every pig that dies. In some cases, sick pigs need to be euthanized and necropsied so as to best ascertain the lesions causing the clinical picture.

Without necropsy, the cause of death cannot always be accurately determined. Again, in the study referenced earlier, the technique of assigning death reasons based on outward appearance of a carcass was only correct about 40% of the cases, when compared to actual necropsy examination.

I often tell producers that the most valuable pig in the barn is the first one that dies. But that is true only if the animal can aid in the diagnosis of potential problems by revealing what caused its death.

Without performing a postmortem examination, it is often difficult to determine the cause of death. Swine veterinarians are the experts at conducting necropsies or autopsies, not only because of their training, but most importantly, because their experience enables them to recognize what is normal and what is abnormal.

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Veterinarians also know which tissues to collect, how to preserve them and which diagnostic laboratory to submit them to.

Producers should never pass up an opportunity to observe lesions when their veterinarian necropsies a pig, and should be ready to ask questions. Curiosity is the best learning tool we possess.

Obtain the tools necessary (primarily a sharp knife) and begin by examining pig mortalities. A digital camera is a valuable tool to preserve images that can later be e-mailed and shared with your veterinarian if he/she cannot visit the production site.

Remember, to understand what “abnormal” looks like, you must first know what “normal” looks like. The primary goal of a necropsy is to determine the cause of death, but always consider a necropsy as a chance to gain valuable knowledge or clues about what is going on in your pigs.

Step 3: Laboratory Confirmation

The final step in the process of diagnosing a problem requires the use of one or more of a myriad of lab tests that have been developed over the years. This confirmatory testing can be done by a veterinary diagnostic laboratory such as a state-supported lab or in some cases by the attending veterinarian at his or her clinic or lab.

The list of suspected causes uncovered in the history and physical exam will determine what samples or specimens should be collected and submitted to the laboratory.

Samples may include pieces of tissue such as lung, intestine, tonsils or lymph node, just to name a few. Or, the test desired may require only blood or serum from the affected or recovered pigs.

It is very important to work with your veterinarian when submitting tissues to ensure the right samples can be collected, prepared and transported in a manner that will give the greatest chance of securing a lab confirmation. If you submit wrong or poorly prepared samples, you will likely not receive accurate or meaningful results.

When submitting tissues for laboratory confirmation, it is very important to choose samples from a pig that died early in the course of disease and represents the problem at hand. Avoid the temptation to send tissues from only chronic, poor-doing pigs because they may not be representative of the disease you are trying to confirm.

It is important to include as much information and history as possible when submitting samples to the lab, since the pathologists will need a list of the differential diagnosis as well as a thorough history and description of the main clinical signs. Your veterinarian will supply this information along with a submission form in most cases.

The laboratory results are the objective portion of the diagnostic process. The results of a lab test tend to be positive or negative, and thus help to eliminate other possibilities that were on the list.

The Cost of Misdiagnosis

I was recently asked: “Which is worse — a wrong diagnosis or no diagnosis?”

In nearly every case, a wrong diagnosis is a bigger issue than having no diagnosis at all. While not detecting a problem early in its course can result in substantial loss, misdiagnosing the problem and setting off on the wrong course of therapy or prevention will delay making the correct diagnosis, plus inflict the cost of the wrong therapy or intervention.

This is particularly true when a diagnosis is made based solely on the physical appearance of the mortality, and the assumption is made that every pig that is found dead, and presents itself in a particular way, can be attributed to a single disease or syndrome.

Hemorrhagic bowel syndrome (HBS) is one such problem that is often misdiagnosed or over-diagnosed. If a postmortem exam or necropsy is not performed on these pigs, the tendency is to diagnose HBS on any unexpected or acute death of an apparently healthy pig. There are many potential causes of death in such pigs, and without a necropsy, the correct diagnosis will never be known.

When the level of deaths attributed to HBS reaches a level that is perceived to require intervention, such as feedgrade antibiotics or the addition of mitigating feed ingredients, the end result will simply be a waste of resources.

In some scenarios, a misdiagnosis that leads to the wrong intervention could allow the true problem to progress or worsen, potentially resulting in even more loss that would have been prevented with the correct intervention.

Interventions are not always therapeutic. Preventive tools such as vaccines are also at risk of being misapplied in cases of misdiagnoses. Certainly, a vaccine intended for ileitis will not reduce mortality due to HBS, and the cost of the vaccine (if not offset by controlling ileitis) would have been wasted.

Avoiding Misdiagnosis

To avoid making a misdiagnosis, first avoid taking preconceived ideas into the process. This is called an “anchoring mistake.” It leads to not considering other options or possibilities when your mind is made up early in the process.

In many cases, the wrong diagnosis results from errors in thinking or judgment. Often, simply looking at or listening to the pigs would have resulted in the correct diagnosis. If the initial attempts at remedying or treating the problem do not work, you must reassess and try again.

It is important to ask your veterinarian and yourself the right questions:

“What else could have caused this?”

“Could there be more than one thing going on?”

Rarely do diseases act entirely alone. Most are multi-factorial and will require a systems approach to resolve them.

Lastly, never stop listening to the pigs! In most cases, the pigs will tell you what is wrong and help you make the right diagnosis.

‘Why Do We Need to Bleed So Many Pigs, Doc?'

Researchers have made great strides in developing and improving the serological tests available for swine. Although the perfect serology test has yet to be discovered, it is important to know both the strengths and weaknesses of any test you plan to use. When used correctly, serology can be a very valuable diagnostic tool.

Serological tests are assessed based on two criteria — sensitivity and specificity. Sensitivity is the measure of how good the test is at identifying animals that are truly infected as “positive.”

Specificity is the measure of how good a test is at identifying truly non-infected animals as “negative.”

If a test tends to mistakenly identify true positives as “negative,” we say it has poor sensitivity. Poor sensitivity tests are prone to producing “false negative” results.

This type of error would be disastrous if, for instance, you were testing boars for porcine reproductive and respiratory syndrome (PRRS) virus prior to using their semen in naïve sows and the test failed to identify an infected boar.

If the test wrongly identifies true negative animals as “positive,” it is said to have poor specificity. A test with poor specificity is prone to producing “false positive” results.

If you are working with a population expected to be negative for PRRS, for example, “false positive” results will likely force you to retest the animals in question to confirm that the test was truly a “false positive.” Too many “false positive” results will add to expense and frustration.

Before you sample the first pig, there are several issues you need to consider. First, why are you testing and how do you plan to use the results? Do you simply want surveillance for the presence (or absence) of a particular disease in your herd, or do you have a need to know the prevalence of a disease that already exists in the population?

You can also use some serological tests to roughly determine when a disease entered and infected a group of animals. This may be valuable in determining the best time to vaccinate ahead of the exposure.

To gain the most benefit from the tests, a basic understanding of what the test is detecting is important. Today's serology tests generally are looking for the presence of the bug itself (antigen) or for the pig's immune system response to the infectious agent (antibody). Not all pigs in a population respond the same, and there are certainly differences between infectious agents as to when and to what degree they express themselves to a given test.

Three statistical factors determine how many samples are needed:

  1. The number of animals in the group or population being tested,

  2. The expected prevalence of the disease being tested among the population, and

  3. The confidence level you wish to achieve with your testing.

For example, in a 1,000-head finishing barn, to achieve a 90% confidence level of detecting a 10% subset of the pigs that are positive for a disease, statisticians have calculated that you must sample 22 animals in order to detect at least one positive in a given time frame.

If you raise the desired confidence level to 95% and lower the suspected prevalence to 5% in the same 1,000-head barn, you must increase your testing to 57 pigs. It really is a numbers game where statisticians make the rules.

Interestingly, as population size goes above 1,000, the number needed for the same confidence and prevalence values does not go much higher. There are published statistical sample size charts that are a handy reference for determining the number of samples required for various confidence and expected prevalence levels. Figure 1 offers an abbreviated version as an example.

Risk aversion may be the determining factor as we decide how many animals to bleed. If you are bringing a small number of gilts (100) into a known PRRS-naive herd, you may want to be nearly 100% confident that a single animal will be detected. If so, the statistics tell us we must test every animal in the group. The problem with this approach is that it often exceeds the specificity of the test, and then you will have to deal with one or more false positive results. False positive results will likely lead to retesting some of the animals using a confirmatory test.

Remember, the perfect test has yet to be discovered. Until it is, we will just have to go on asking: “Why do we have to bleed so many pigs, Doc?”
John T. Waddell

Figure 1
Number of Samples
Expected prevalence 10% 5%
Confidence level 90% 95% 90% 95%
Population size
50 18 22 30 35
100 20 25 37 45
500 22 28 43 56
1000 22 29 44 57

Are Sows Being Culled for the Right Reasons?

Pork producers and breeding herd managers typically record a single reason for culling a sow. Often, they simply check a box in their recordkeeping program without reporting other health-related conditions that may be occurring simultaneously.

Classifying cull sows into various categories is done by lay personnel and serves as an evaluation of health status, which is frequently used to make management decisions.

Many recordkeeping software systems do not allow producers to record multiple reasons for culling a sow. Typically, the reason for culling is based on external signs and does not incorporate evidence of internal lesions or diagnostic testing results.

Evaluating sow carcasses at harvest plants presents an opportunity to confirm the reasons recorded on the farm and characterize the factors that may cause sows to be culled. Studies that investigate the presence of gross lesions in harvest plants are few.

Postmortem examinations of sow reproductive organs can potentially identify the reason for reproductive failure. A comparison of the on-farm culling records and the observations made at the plant can provide a means of evaluating the accuracy of recorded culling codes.

Standardizing Culling Codes

A retrospective cohort study compared reported reasons for culling with production data and lesions observed at harvest. Records on 923 uniquely identified sows from eight conventional, farrow-to-wean farms with common standard operating procedures were collected at two harvest plants in the Midwest. Individual production records and the reason for culling were obtained.

Criteria were established to identify sows that did not match the culling codes of old age, did not conceive, anestrous, poor body condition, farrowing productivity and cesarean section.

Old age was considered an appropriate culling code if a sow was greater than Parity 5. Sows typically reach maximum body weight at the fifth parity; therefore, sows culled at or before their mature size is reached, arguably are not old.

The “did not conceive” code was considered an accurate culling reason if sows had not conceived within 45 days after weaning. The 45-day limit was established by adding three days for an early return to estrus after weaning and two normal, 21-day estrous cycles. This was consistent with procedures reported by farms participating in the project.

Anestrous was considered an acceptable culling code if sows were culled eight or more days after weaning. The eight-day limit is considered at the upper range of a normal wean-to-estrus interval and anestrous could not be definitively determined prior to this time.

Body condition was considered an acceptable reason to cull a sow if body condition score was less than 3. Body condition score was evaluated prior to slaughter using a scale of 1 (thin) to 5 (fat) [See Body Condition Scoring Guidelines in “Managing Sows in Gestation” Blueprint, National Hog Farmer, April 15, 2006].

Farrowing productivity was established as an acceptable culling code if sows had poor number born alive, poor number weaned, or poor milking ability and were culled at Parity 2 or greater.

Culling Parity 1 sows for poor litter performance was considered unacceptable because those traits are lowly heritable, indicating there is a large environmental influence.

Culling codes that could not be evaluated at the harvest facility, such as lameness, prolapse and other illnesses and management reasons, were accepted as correct without evaluating additional criteria.

Although lameness could not be determined at the harvest facilities, front and rear foot lesions were evaluated and recorded at the harvest facility. Foot lesions included cracked hooves, pad lesions, abscesses on any surface of the foot, overgrown toes and missing dewclaws.

The culling codes of “not found, unknown” or “sudden death” were not acceptable because the sows being evaluated made it to the harvest facility; therefore, those sows were in fact found, and were actively culled for some reason.

The Real Reasons Sows Failed

Of the 923 sows evaluated, 209 (23%) appeared to have had an inaccurate reason recorded for why they were culled. (See Table 1.) The relatively high frequency of culling code errors could result in health, management and financial decisions being based on erroneous information.

Taking a closer look at the individual reasons for culling, old age was improperly recorded in 19% of sows. Of the 322 sows recorded as being culled for old age, 40 (12%) were culled more than 21 days after weaning, 10 (3%) were Parity 5 or younger, and 12 (4%) were culled more than 21 days after weaning and were Parity 5 or younger.

In the study, sows from all parities (1 to 13) were identified as being culled for “old age.” Farms that cull for old age at a specific parity automatically forces the parity average down. This management practice changes herd parity distribution and may make it increasingly difficult to reach the point at which the average sow pays for herself — approximately three parities.

The code “did not conceive” was inappropriately recorded in 48 of 172 (28%) sows culled for this condition. Of the 48 sows culled less than 45 days after weaning, 43 (88%) were culled 29 to 44 days after weaning, indicating they may have been given just one opportunity to conceive.

Anestrous was inaccurately recorded in a relatively small proportion — 7 of 123 sows (6%). Within 30 days of weaning, 59 (48%) were culled for anestrous.

Body condition was improperly recorded in 31 of 90 sows (34%), meaning those sows had a body condition score of 3 or greater at slaughter. Of the 90 sows culled for body condition, 63 (70%) had a body condition score of 1 or 2. And, of the 73 sows with a body condition score of 1, only 27 (37%) had a culling code of poor body condition recorded at the farm.

Farrowing productivity was not appropriately recorded in 23 of 73 sows (32%). Of the 73 sows, 16 (22%) were culled at greater than 21 days after weaning, five (7%) were Parity 1 sows, and two (3%) were culled at greater than 21 days after weaning and were Parity 1 sows.

In addition to the 23 sows with an improper culling code, 16 (22%) averaged more pigs born alive/litter/parity than the study average (10.93). However, since the farrowing productivity code used by several farms represented poor number born alive, number weaned or milking ability, determining the underlying productivity reason for removal using this culling code was not possible.

Cesarean section was unacceptably recorded in 14 of 15 (93%) sows. Of those, 13 (87%) were pregnant at the harvest facility. The Cesarean sectionculling code appeared improperly applied because sows often die or are euthanized following the procedure.

Lameness was recorded as the culling code for 83 sows; as previously noted, lameness was not evaluated at the harvest facility. What we were able to observe and count were the number of lesions (cracked hooves, foot pad abrasions, abscesses, missing dew claws, etc.,) on each foot. The number of lesions per foot and per animal were then totaled.

Total number of front foot lesions in the lameness culling code tended to be higher (P 0.05) between the lameness culling code and the other culling codes combined (1.19 vs. 1.16). Although the presence or absence of foot lesions was recorded in the current study, the relationship between the severity of foot lesions and lameness was unknown.

Prolapse, other illness and management were recorded as the culling codes for 11, 8 and 2 sows, respectively. Prolapses were confirmed in 4 of 11 sows from harvest facility research.

Not found, unknown and sudden death were recorded as the culling codes for 18, 5 and 1 sow, respectively.

Based on the study's findings, herd investigations and interventions that rely heavily on farm reported assessments of clinical condition may have significant limitations.

Differences within and between farms, despite common management and standard operating procedures, suggest that developing health interventions in integrated systems will still require assessment of individual farm characteristics and management. Training farm personnel in the correct diagnosis and reporting of clinical conditions of sows could be very beneficial.

Table 1. Frequency of Sow Culling Codes and Improper Culling Codes From Eight Farms Within an Integrated U.S. Production System
Cull code Frequency % Frequency of improper culling codeb %
Old agea 322 35 62 19
Did not conceive 172 19 48 28
Anestrous 123 13 7 6
Body condition 90 10 31 34
Lameness 83 9 0 0
Farrowing productivity 73 8 23 32
Not found 18 2 18 100
Cesarean section 15 2 14 93
Prolapse 11 1 0 0
Other illness 8 1 0 0
Unknown 5 1 5 100
Management 2 0 0 0
Sudden death 1 0 1 100
Total 923 100 209 23
aAverage parity at removal of culled sows = 5.44.
bCulling codes not meeting defined criteria.

Foreign Animal Disease Preparedness is the Key

Exposure to a foreign animal disease could have devastating effects on the U.S. pork industry. It is important to understand how such an animal disease disaster would unfold. Advanced preparation and swift action are the keys to minimizing the impact.

The average pork producer probably doesn't spend a lot of time thinking about foreign animal diseases. But it is important to have a basic understanding of what occurs during an animal disease disaster and the roles individuals would play in such an event.

Economic Effects

The economic impact of a foot-and-mouth disease (FMD) outbreak in the United States has been estimated at $14 billion — roughly 9.5% of U.S. farm income.

Losses in gross revenue for live hogs and pork products in the United States are estimated at 34% and 24%, respectively, according to a 2002 Journal of the American Veterinary Medical Association article written by P.L. Paarlberg, J.G. Lee and A.H. Seitzinger.

A significant portion of the projected loss would result from closing of export markets, which account for approximately 15% of U.S. pork production and contribute an additional value of $23/head domestically.

Similar economic effects could be expected for a case of classical swine fever or other foreign animal diseases that have the ability to rapidly spread through the swine industry.

The loss of export markets is not the only repercussion when a foreign animal disease is discovered. On a national scale, the aggressive disease control measures enacted by animal health authorities to prevent further spread of a foreign animal disease will affect the movement of live pigs, fresh pork and pork products, locally and interstate.

Jointly, the loss of export markets and the restricted movement of pigs and pork paints a grim picture and underscores the importance of preparedness.

The better prepared the industry is to detect and respond to the introduction of foreign animal disease, the quicker and easier it will be for the industry to fully recover.

Focus on Early Detection

The early detection of a foreign animal disease in the U.S. swine herd is critical for mounting an effective disease response.

Because they observe their animals every day, pork producers play an important role in early detection. When disease problems arise, utilizing a herd veterinarian to determine the cause is critical.

The producer-veterinarian relation-ship is a powerful tool toward early detection of potential foreign animal diseases, especially when pork producers and veterinarians have a greater awareness of the symptoms and an understanding of how to report a suspect case.

Foreign Diseases of Swine

Foot-and-mouth disease, swine vesicular disease, vesicular stomatitis, classical swine fever (hog cholera) and African swine fever are animal diseases not present in the U.S. swine herd today.

A confirmed case of any of these diseases in the U.S. swine herd would affect the industry's ability to export pigs, as well as limit interstate commerce. Luckily, producers don't need to know the intricate details of each of these diseases in order to increase their awareness. The clinical signs can be broken down into two general categories — swine vesicular diseases and swine fevers.

Swine Vesicular Diseases

Foot-and-mouth disease, swine vesicular disease and vesicular stomatitis fall into the category of swine vesicular diseases. All cause blisters, which usually pop early and cause raw spots (excoriations) inside the mouth, on the snout, around the coronary band (top of the hoof) and between the toes.

In general, pigs affected with the early stages of these diseases have a high fever, refuse feed and are lame. In the later stages, pigs can get secondary bacterial infections of the raw spots and slough their hooves. These diseases usually don't cause mortality in older pigs, but some piglets may die and some sows may abort their litters.

Diseases currently circulating in the swine industry do not cause these types of outward appearances, so whenever these signs and symptoms do occur, producers should always be suspicious of a foreign animal disease.

If seen, it is important to immediately report these conditions to the herd veterinarian or directly to animal health authorities. See pictures of the vesicular diseases shown here and on the attached poster.

Swine Fevers

Classical swine fever and African swine fever fill the swine fever category. Weaned pigs infected with these diseases can have a high fever; go off feed; have splotchy, red, skin discolorations; diarrhea; and hind limb weakness. Mortality rates can exceed 30%.

These diseases can cause rapid mortality, or pigs may develop drawn-out, chronic symptoms. Unfortunately, many of the clinical signs of the swine fevers are mimicked by current diseases in the swine industry — particularly porcine circovirus-associated disease (PCVAD), erysipelas and salmonella. This presents a problem because producers may have dealt with these domestic diseases, so seeing the clinical signs may not trigger suspicions that a foreign animal disease could be present. This underscores the importance of using your herd veterinarian for disease diagnostics when clinical signs appear.

Timely Disease Reporting

When a foreign animal disease is suspected, producers have two options — report the suspect case directly to state animal health authorities or contact your herd veterinarian immediately.

In most cases, the herd veterinarian is more familiar with state animal health authorities and knows how to contact them. Regardless, producers should have the contact information for their state animal health authorities readily available. The attached poster provides space to list contact information for the herd veterinarian, state animal health authorities, premises identification, full site address and the primary contact person.

Foreign Animal Disease Investigations

Any time state animal health authorities are notified that a foreign animal disease may be present, they will initiate a foreign animal disease investigation. Investigations are a free and confidential service provided by state animal health authorities for early detection of foreign animal diseases.

State veterinary authorities who have received training at the Plum Island Animal Disease Center to qualify them as foreign animal disease diagnosticians (FADD) will investigate.

Once reported to state authorities, the goal is to have a foreign animal disease investigation completed on the same day. The diagnosticians work closely with the herd veterinarian and the pork producer to investigate and collect the appropriate laboratory samples to determine if a foreign animal disease is present.

During the investigation, foreign animal disease diagnosticians provide important information to the producer on the steps to prevent disease spread while the investigation is occurring. Most investigations are resolved within 24 hours. Unless there is a positive diagnosis of a foreign animal disease, producers are allowed to get back to business.

It is important for pork producers to understand that these investigations are fast, free and confidential. Hundreds are done across the country every year. Most turn out to be negative for a foreign animal disease.

These investigations are also a critical component in national disease surveillance programming. The ability to rapidly prove that a foreign animal disease is not present provides a level of confidence that the U.S. swine herd is free of foreign animal diseases. This confidence helps the pork industry maintain and expand its export markets. Pork producers play a direct role in supporting the industry's export markets.

Disease Response

If a foreign animal disease outbreak occurs, such as foot-and-mouth disease, state animal health authorities have to accomplish very specific actions in order to get a disease controlled and eradicated.

First, they must establish the appropriate control area and a surveillance zone around the infected farm. This defines the area where disease control measures and resources will be targeted.

Next, they will identify and classify farms with susceptible species in the control area that are directly exposed or at risk of exposure due to their proximity to the infected farm. Authorities will also identify industry assets, such as sale barns, buying stations, packing plants and county fairgrounds, within the control area.

Once the premises and assets are identified, state officials must communicate important information for disease identification and reporting, plus the disease control and biosecurity measures required to prevent further disease spread. Once contained, animal health authorities can focus efforts on eradicating the disease and the surveillance programs necessary to prove disease freedom. The faster all of these steps can be accomplished, the sooner producers can resume normal business operations.

Proactive Producers

During a foreign animal disease disaster, time is money. Successful business continuity during an animal disease disaster relates directly to the speed in which all cases of a disease are identified and controlled, the appropriate surveillance methods are initiated, the unaffected regions are identified, and the biological risk management programs (biosecurity) are implemented.

The easiest step producers can take to help prepare for a foreign animal disease outbreak or a natural disaster affecting livestock is to register their premises at the state level. Premises registration provides state animal health authorities with a data point on the map and corresponding producer contact information that allows officials to respond faster.

If an animal disease disaster occurs, premises identification and the National Animal Identification System will aid animal health authorities in identifying and certifying disease-free regions or compartments. This capability will help the industry more rapidly reestablish commerce interrupted by the aggressive disease control measures put in place at the state and national levels.

Pork producers should take advantage of animal disease disaster and foreign animal disease awareness training provided by state animal health authorities, county emergency managers or Extension offices. This training will increase awareness and help producers understand the effects of a foreign animal disease in their local communities. In addition, producers should work with their veterinarian to review biosecurity protocols to ensure they have procedures in place to prevent disease introduction.

The high impact of foreign animal diseases on the U.S. economy deserves special consideration, even when the risk of disease introduction is small.

Bottom line — the swine industry would be significantly affected by these diseases. Our level of preparedness as an industry will make a major difference in how quickly we will recover. Producers who take the time to increase their awareness play a critical role in increasing the overall preparedness of the swine industry.

More Effective Disease Diagnostics

Recent widespread outbreaks of porcine circovirus-associated disease (PCVAD) in North America have served as a dramatic reminder that infectious diseases can be devastating to pigs and profits.

And, it's not as if porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus, ileitis, or any of the “old” diseases, such as Mycoplasmal pneumonia, have gone away.

Fortunately, there are effective approaches for dealing with most of these challenges. Putting a plan together to prevent, control or eliminate specific diseases starts with an accurate understanding of the health status of swine populations.

Perhaps “health status” is the wrong choice of words, since health and disease tend to be quite dynamic in many pig populations.

To keep track of these health dynamics, the producer, veterinarian and diagnostic laboratory must work together in a partnership to develop diagnostic approaches that are effective and worthwhile. Each party brings key expertise that is essential for accurate and timely disease diagnosis.

Understanding the normal production and health dynamics within a herd is the foundation for early detection of disease. Early detection is the key for effectively managing endemic, emerging and exotic disease problems.

The Partners

The producer, veterinarian and diagnostic laboratory all have important roles in keeping tabs on the health of pig populations.

The point person in tracking herd health dynamics is the producer/animal caretaker. The producer sees the pigs every day and is the first to observe changes in performance or clinical signs of disease. Therefore, the producer is the “expert” on a particular group of pigs. He/she knows, for example, how the pigs looked last week, or how the previous group of pigs looked or performed. These are important details for a complete understanding of why a group of pigs is performing as they are.

Next in the herd health partnership are the veterinarians with their specialized training and knowledge in disease diagnosis, treatment and control. They are trained to recognize the clinical signs associated with specific diseases, and the sampling and submission procedures necessary for effective diagnostic testing in the laboratory. Veterinarians know and understand the diagnostic tests available for different diseases, and how to interpret the various tests as they relate to the clinical history of the farm.

Veterinarians offer a different perspective by benchmarking the client herd against other similar herds, and through an awareness of pig health concerns in the geographic area. Working with the producer, the veterinarian is able to develop appropriate health monitoring programs as situations and producer goals dictate.

To be most effective, veterinarians need to understand the health status and goals of a herd, and then work closely with producers to achieve those goals.

The third member of the health monitoring team is the veterinary diagnostic laboratory. Many swine practitioners provide some degree of diagnostic service in their practice. However, veterinary diagnostic laboratories provide more specialized equipment, knowledge and service. These labs develop, validate and conduct diagnostic tests, and maintain a portfolio of diagnostic procedures for working up different types of cases.

In addition, diagnostic labs serve as a resource for veterinarians; advise on test selection and interpretation of results; and provide current information on disease trends regionally, nationally and even globally. Diagnostic laboratories also maintain key relationships with disease researchers, other diagnostic labs and animal health regulatory officials.

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Baseline Monitoring — Production Performance

A good understanding of the herd baseline performance facilitates more rapid diagnosis of new diseases, helps direct testing strategy and streamlines interpretation of diagnostic results. Only by knowing the “normal” performance or health of a herd, can the producer or veterinarian identify the “abnormal” situations or diseases that may arise.

Tracking baseline performance relative to disease status also allows cost-benefit analyses of health interventions for existing diseases, providing a yardstick for measuring response to treatment/control measures. Baseline production performance monitoring includes such measures as average daily feed intake and water disappearance, individual treatment, mortality (adjusted for season, gender, etc.), pulls or culls and average daily gain.

An obvious and very important monitoring tool is the daily observation of pigs for clinical signs of disease. A consistent method of observing pigs can detect changes earlier and increase the success of treatment interventions.

It is important to remember three characteristics of most disease outbreaks in pigs:

  • Only a small portion of the group might be affected at any given time.

  • Important clinical signs, such as coughing or pigs going off feed, generally start as very subtle changes.

  • Early detection usually results in improved response to treatment.

To recognize these early, subtle changes, it is important to have a consistent and structured approach to walking the pens and observing the pigs (see sidebar on page 10).

Changes from normal performance can also include unusual lesions in pigs that are identified during a postmortem examination. Some producers work with their veterinarians to develop the skills necessary to perform postmortem exams. These skills must not be taken lightly. Every precaution must be taken to avoid exposure to enzootic disease.

Routine examination of carcasses for common causes of death, such as gut torsions or gastric ulcers, helps a producer become more aware of what occurs routinely in their herd, allowing more rapid detection of abnormal findings.

Performing postmortem examinations keeps the mind, eye and knife sharp, and improves the odds for early detection of new health problems.

Tracking baseline performance allows producers and veterinarians to establish triggers for action or thresholds for intervention when a particular factor exceeds a set value or changes from the normal, background level. This becomes part of a set of formal or informal farm standard operating procedures developed by the producer and herd veterinarian, by which performance is continuously monitored and compared to the baseline.

Baseline Monitoring — Disease Detection

Actively monitoring a herd for specific disease agents is another important tool for understanding the baseline performance in a herd. There are several different approaches for monitoring health status in pigs, but a brief overview of the basic diagnostic methods may help clarify how the different methods are applied.

Generally, when searching for specific disease agents, we use two approaches — searching for the agent directly or searching for evidence or clues left by the disease agent indirectly.

Finding the agent directly may be possible by visual detection. For example, some internal parasites of pigs are visible without magnification and eggs can be seen with microscopic examination of fecal samples.

At the other end of the spectrum, an electron microscope can magnify thousands of times to see the specific size and shape of Transmissible gastroenteritis (TGE) or rotavirus particles in a fecal sample. This confirms the presence of the virus in the sample.

A common method for directly detecting bacteria and viruses is to amplify the number of organisms by culturing them. With bacteria, the colonies are visible and can be further tested to identify the specific bacteria isolated. Viruses, on the other hand, cause changes in the cell cultures in which they are grown. Further testing provides positive identification.

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The advantage of growing the organisms is that they can be available for further testing or for use in autogenous vaccines, when appropriate. The disadvantage is that the procedure can be slower (in the case of virus isolation), and not as sensitive (less likely to find all positive cases) than some other methods.

Another method commonly used to directly detect bacteria and viruses is the polymerase chain reaction (PCR) test. This method is used to amplify the genome (DNA or RNA) of specific disease agents up to levels that can be detected by various means. PCR tests for several viruses (PRRS virus, Type 2 circovirus, swine influenza virus, TGE, classical swine fever) and bacteria (Lawsonia intracellularis for ileitis, Haemophilus parasuis, Actinobacillus pleuropneumonia, Actinobacillus suis, Erysipilothrix rhusiopathiae for erysipelas, and Leptospira sp.) have been developed for routine use at diagnostic laboratories.

PCR tests are generally faster and more sensitive than other methods for detecting disease agents directly. Because they are so sensitive, great care must be taken in handling tissues to avoid cross-contamination and false positive results.

In addition to finding disease agents directly, we also look for evidence of the disease agents by various methods.

A common tool used for monitoring swine health is serology, in which the serum component of blood samples is tested for antibodies that are produced against specific disease agents. Sometimes several tests are available for the same disease, but the basic principle of finding the antibodies is the same.

The advantage of using serology is that antibodies against the disease agents tend to last longer than the actual agent, so there is more time for detecting the agent. The disadvantage is that it can be days to weeks after infection before the antibodies appear in the serum, so it is less useful in the early stages of a disease outbreak.

Additional indirect evidence that a disease agent is present is the change it can cause in the pig, either outwardly (clinical signs) or by changes to tissues that are evident grossly or microscopically.

Observation for clinical signs was discussed earlier. More detail on postmortem examination is covered elsewhere in this issue. However, it is important to note that when evaluating gross lesions in diseased pigs, it is only possible to make a presumptive diagnosis — an educated guess — as to the specific disease causing the lesions. This is because the body has a limited range of possible reactions to disease, so the lesions caused by one disease may overlap with others. This is the reason for laboratory confirmation of a presumptive diagnosis.

The microscopic lesions caused by specific disease agents are central to pulling the diagnostic story together. Here, too, the lesions are sometimes nonspecific, especially when pigs are chronically affected with multiple infections. Still, the microscopic lesions are critically important, for example, in diagnosing PCVAD in pigs, since many pigs examined will test positive for the virus whether they have the disease or not. In these cases, the diagnosis requires a combination of typical clinical signs, specific microscopic lesions and the presence of the virus within the affected tissues. In other words, effective diagnosis requires input from all of the diagnostic team.

Infectious agents do not cause all health challenges. Many chemical compounds are associated with poor performance and even mortality in pigs when deficiencies or toxicities are allowed to develop. Testing directly for these compounds in tissues, feed or water is an important diagnostic capability performed by specialized laboratories.

Monitoring Refinements

Very often the diagnostic question goes beyond simply whether or not a disease is present. For example, it may be important to understand the level of activity of diseases at specific ages, such as the presence of PRRS virus or Mycoplasmal pneumonia at weaning, or the presence of antibodies against swine influenza in nursery pigs. This information is used directly in making health and production management decisions such as use and timing of vaccines and medications.

There are also instances when more information about the specific strain or type of a virus or bacteria can be useful. For example, keeping track of genomic sequence information on PRRS viruses isolated from a farm can be used to determine whether an “old” virus circulating in the herd caused a new outbreak or if a new virus has been introduced.

Similarly, subtyping bacteria, such as Haemophilus parasuis, has been used to determine whether clinical disease is the result of bacteria that are already present in commercial or autogenous vaccines.

Develop a Plan

The final step is pulling the diagnostic story together so that an action plan can be implemented. This step requires the input of the producer regarding the pig population (ongoing clinical signs, response to treatments, etc.); the interpretation of the diagnostic results by the veterinarian; and, perhaps, the diagnostic laboratory.

It is important to emphasize that diagnostic testing should not be initiated unless you know how you will apply the results. Diagnostics are an integral part of an overall herd health and biosecurity plan. The key word is “plan.” The return on investment from applying diagnostic tests comes from using them as a part of an overall herd health strategy.

There are many case studies demonstrating successful partnering by producers, veterinarians and diagnostic laboratories.

A dramatic example includes a case in which PRRS PCR testing was performed on a large scale to eliminate PRRS-infected breeding stock, shortly after moving into a herd from an isolation facility that was infected in the late stages of quarantine. In this instance, the producer and the veterinarian had set herd health goals and established a plan of action in the event of a PRRS virus infection.

The infection was detected through active monitoring of the incoming replacement breeding stock for PRRS, according to the plan. Because of the veterinarian's relationship with the diagnostic laboratory, the testing capabilities of the lab were well understood and were immediately set into motion.

In the end, the technical expertise of the laboratory and the timely testing was accomplished and reported. This allowed for a successful test and removal of infected pigs, which prevented a costly infection of the breeding herd.

All of these elements — effective partnering, established herd health goals, plans for diagnostic testing and the subsequent response — are essential for efficient and effective management of the dynamic health environment of pig populations.

Circle the Barn, Circle the Pen, Circle the Pig

To be confident that subtle changes truly reflect a change in pig health, it is important for producers to develop a consistent observation technique that can be applied every time you check a barn.

Daily observation of pigs for clinical signs of disease is a very important herd health-monitoring tool. A consistent method of observing pigs will help detect changes earlier and increase the odds that a successful treatment or response will be found.

If your approach to checking pigs in a facility varies from day to day, the small changes you see might simply be the result of viewing the pigs differently.

Often, early disease is accompanied by changes in feeding behavior. But we also know that pig activity and feeding behavior changes during the day. If you observe pigs during their peak feeding activity — generally in the morning during summer months — but check the pigs in the afternoon the next day, the differences in feeding behavior may not be significant.

Likewise, if an incomplete or random approach is used, the most obvious clinical signs (i.e., coughing) and less severe signs (i.e., mild lameness) that might help understand and diagnose the problem, may go unnoticed.

There are many ways to standardize observations. The key to developing a standard method is to find one that is thorough, consistent and comfortable.

Here's an example of consistent observation in a finishing barn with small pens and a central alleyway:

Start at the entrance to the barn. Think in terms of three successively smaller circles — circle the barn, circle the pen, circle the pig.

Begin at the first pen on your right side and move pen by pen down that side of the barn, ignoring anything on the opposite side of the barn.

At each pen, evaluate the entire pen thoroughly — starting at the front left corner and looping your visual pattern around the pen in a circle. Make sure to look directly at each pig, the feeder, the water source, the floor, the pen walls and the gates.

The goal of this first pass is to identify any pigs that appear to be abnormal in activity, posture or mobility, or have obvious signs of illness. Pen walls and floors should be viewed for evidence of diarrhea or blood from wounds. Be sure water is available — the floor below the water source should not be dry. Confirm that the feeder is providing clean, dry feed. Repeat this process with each pen.

Any pig that appears to be different from its penmates in terms of activity, posture, mobility or obvious signs of illness, such as respiratory difficulty, should then be observed using a thorough, systematic circling procedure focused on the pig.

Begin at the head, checking the eyes for excessive discharge or redness and the nose for discharge. Follow along the top and back of the pig, checking its physical condition. If you can see the pig's spine, it's likely the pig has not eaten well for several days.

At the rear of the pig, check for signs of tail or vulva biting and diarrhea. Severe scours with watery diarrhea might not be as obvious as staining of the legs. However, you might observe a reddened, irritated area around the anus. Excessive tail movement with the tail curled down may be a sign of irritation.

Moving forward along the pig's underline, observe both rear legs for abnormal posture, redness or swelling of the joints and a willingness to put full weight on both feet. Follow the flank forward to assess fullness of the belly — an indication of feed intake. Abnormal flank movements may indicate respiratory problems. In severe cases, you may observe “thumping” motions. Evaluate any signs of wounds or injuries. Repeat this evaluation on the front legs.

When you have completed the right side of the barn, turn and check all of the pens on the other side.

The three-circle approach, applied systematically, improves your chances of seeing the important clinical signs of health problems and leads to faster, more accurate diagnosis and intervention.
Locke Karriker, DVM

Educational Materials Increase Awareness of Classical Swine Fever

Educational materials have been developed to ramp up awareness of classical swine fever (CSF) and complement the surveillance program that is in place, according to Harry Snelson, DVM, director of Communications for the American Association of Swine Veterinarians (AASV).

AASV, the National Pork Board and Iowa State University have joined in a cooperative agreement with the U.S. Department of Agriculture (USDA) to launch a new video on CSF that provides updated information. The video features a mock scenario of a hog farm in the Southeast, and how a mixed-practice veterinarian deals with a potential foreign animal disease introduction.

To add interest and harken back to the days when CSF or hog cholera was a concern in the United States, 3-D glasses must be worn to view the video shown by a special projector. There is some indication that viewers retain information presented in 3-D better than information viewed in conventional formats.

“CSF — The Differential We Can't Afford to Forget,” premiered at the AASV annual meeting in early March in Orlando, FL.

CSF may be confused with a variety of swine diseases, including acute pasteurellosis, African swine fever, erysipelas, Haemophilus parasuis, leptospirosis, porcine circovirus-associated disease, porcine reproductive and respiratory syndrome, salmonellosis, Streptococcus suis and septicemias.

Production of the video arose out of a new CSF Surveillance Program that USDA has developed, says Dave Pyburn, DVM, of USDA's Animal and Plant Health Inspection Service.

That new surveillance effort involves sampling from several populations in the field, including feral swine captured by Wildlife Services, diagnostic cases submitted to participating diagnostic laboratories, and slaughter swine that are condemned for diseases that look like CSF, he adds.

“We also wanted to educate veterinarians in particular on what CSF looks like and how it can mimic endemic diseases that we already have here; then, to make the surveillance effective, we want swine veterinarians to send in tonsils for testing with their diagnostic cases,” Pyburn stresses.

There are two reasons for submitting tonsils, he points out. First, the tonsil provides a good diagnostic sample for many swine diseases, and second, the USDA is in the process of validating a polymerase chain reaction test that can quickly test for the presence of CSF.

“That's why we want veterinarians to turn in tonsils so we can pull those out of diagnostic lab cases, and those pigs then become part of our surveillance stream under this CSF surveillance program,” Pyburn notes.

“The whole message is that veterinarians see certain diseases all of the time — salmonella, septicemia, etc., but they can't tell them apart from Classical Swine Fever,” explains Paul Sundberg, DVM, vice president of Science and Technology for the National Pork Board. “The only way you can tell is to send the tonsils to the diagnostic lab.”

“The point is that now, when the tonsil is submitted, it will be eligible to be tested for CSF through USDA's National Animal Health Lab,” adds Snelson.

When a diagnostic lab pulls a tonsil and submits it for the CSF Surveillance Program, the veterinarian submitting the tonsil will receive a $50 credit at the diagnostic lab as an incentive to participate, says Pyburn.

The surveillance program was launched last year, and about 8,000 nasal swabs and tonsils were submitted through diagnostic labs.

To further the CSF surveillance program, Pyburn says the new video will be shown at veterinary schools and veterinary meetings. Regional sessions for accredited veterinarians will also be conducted, some held in conjunction with state veterinary programs.

Plans are to also develop an interactive computerized module that would assist in tissue selection for specific disease diagnostics and aid in differentiating diseases such as for CSF, he says.

Postmortems, Herd History Help Find Effective Answers

The emergence of porcine circovirus type 2 (PCV2) in the Midwest in the last year has forced producers to refocus on the nursery and finishing phases of production. We continue to battle a wide range of preexisting pathogens, including porcine reproductive and respiratory syndrome (PRRS), swine influenza virus (SIV), Mycoplasmal pneumonia, Haemophilus parasuis, Actinobacillus suis and Streptococcus suis. And Porcine Respiratory Disease Complex (PRDC) is a bigger economic issue than ever.

When mortalities occur on any farm, the postmortem (posting) exam may be the most valuable tool in determining the cause of pig deaths. It allows us to make a quick, initial diagnosis of the pathogens that may be involved so an early treatment protocol can be put into place. A diagnostic laboratory then confirms this initial diagnosis.

The pathology report that you receive from the diagnostic laboratory contains a large amount of information, including the presence of viruses, bacteria and parasites, plus bacterial sensitivities and histopathology reports (microscopic changes in the tissues) that help to determine whether or not the pathogens found are significant.

We consider tissue submissions to be a very good diagnostic investment due to the amount of information received relative to the expense. Polymerase chain reaction (PCR) tests and virus isolation results also provide a source of virus that can be used for additional sequencing information to help characterize the strain or subtype of virus present. The control program often requires this specific information.

Information from the pathologist's report then drives the treatment recommendations and future diagnostics. Bacterial antibiotic sensitivity reports indicate which antibiotics should be effective in controlling bacterial pathogens that are causing problems. Your veterinarian can develop a treatment protocol using this information, coupled with his knowledge of the antibiotics that will effectively reach the target organs. In cases where the sensitivity report shows that multiple antibiotics are available and appear to be effective in pigs, the decision-making process may include a cost comparison.

Injectable antibiotics are the most important part of any treatment protocol involving bacterial pathogens, but water-soluble and feedgrade antibiotics may also be used in the treatment program.

Additional diagnostics, such as serum profiling of different age groups, might be useful to identify the age when pigs are becoming infected. This information can be helpful for prevention and control strategies.

The diagnostic lab's report may be even more valuable in a consistent flow of pigs when it is used to take preventative actions in younger groups to “get ahead” of problems before they occur. Preventative actions might include changes in management or pig flow, changes in vaccination protocols or the use of strategically timed medication programs, to name a few.

When your veterinarian arrives to post pigs and collect tissues for the diagnostic laboratory, a complete history should be taken. This history gives the diagnostic laboratory background information on the group of pigs, and serves as a good way to review what actions the producer has taken. It can also help guide future interventions based on the effectiveness (or lack of effectiveness) of these past interventions. It may also uncover something that has been missed.

The diagnostic laboratories' tissue submission form can serve as a guide in taking this history, which should include:

  • The age of the pigs submitted;

  • The date and time of pig death;

  • Whether the submitted pigs were euthanized;

  • The number in the affected group, including the number of pigs that are sick and dead;

  • The duration of the problem;

  • The type of housing;

  • Any treatments or vaccinations the pigs have received;

  • Major clinical signs and clinical diagnosis; and

  • A description of the postmortem findings.

Realizing that postmortems and tissue collection can help zero in on the cause and effective treatment of a herd health problem, following are five pitfalls to avoid when conducting those examinations:

  1. Failure to conduct postmortem examinations.

    Veterinarians are specifically trained to effectively conduct postmortem exams; however, producers and managers are often called upon to assist with collecting, preserving and shipping samples for laboratory analysis.

    Due to the large scale of many hog operations today — both in numbers of pigs and geographically — it is not always possible for a veterinarian to get to the site to conduct postmortem exams in a timely manner.

    For producers who are interested in learning proper posting procedures, it is critical to spend time with a veterinarian to learn pig anatomy and effectively collect samples. Some veterinarians have found it helpful to have producers accompany them to a packing plant to do slaughter checks. This is a good way to see a lot of normal anatomy and, possibly, some abnormal anatomical conditions.

    Digital cameras have been useful tools for producers to e-mail pictures of posted pigs for a conditional opinion. Digital photos and the color calibration of computer monitors present some major challenges to overcome, but some gross analysis can be made in specific circumstances.

    In difficult cases, pigs can be delivered directly to the diagnostic lab to get the very best results, since there is no delay between postmortem and testing of the tissues.

    Some causes of mortality are easier to diagnose than others. Submitting the proper tissues in adequate quantities to the laboratory increases the odds that the correct pathogen is identified. If a diagnosis has previously been made, posting pigs can help verify whether the diagnosis was accurate or if circumstances have changed.

    As a rule, the most accurate results will be achieved when your veterinarian conducts the postmortem exam and submits the tissues to the diagnostic laboratory to confirm a preliminary diagnosis.

    The veterinarian will follow up with the results of the laboratory diagnosis, and present an action plan to treat or manage the problem and/or prevent future occurrences. It is a mistake not to post pigs. We must try to learn from past failures (dead pigs) to succeed in the future.

    It is vital to identify groups of “at risk” pigs quickly. New tools are becoming available to help monitor groups of pigs to quickly identify increased mortality so that postmortems and corrective action can be taken to reverse a bad trend.

    Figure 1 is an example of Metafarms' Mortality-by-Week-on-Feed report. It shows a dramatic spike in mortality in the fourth week after pigs are placed in finishing. Real-time recordkeeping systems such as this are helpful for monitoring losses in large systems.

  2. Failure to post the “right” pigs.

    Groups of pigs with a high mortality rate can look dramatically different from one group to another. Some mortalities occur as “sudden” or “unexpected” events, where apparently healthy pigs are found dead the next day.

    Pigs in another group may have more warning signs and, by the time they die, appear more as chronic cases. In those cases, it is tempting to simply post the dead pigs and submit tissues. However, the diagnosis from these pigs may be different from what caused the initial problem.

    Chronic pigs may have more secondary infections, and may have received antibiotic treatments that inhibited growth of bacteria at the lab. In that situation, it may be necessary for economic reasons, as well as for the welfare of the group, to sacrifice pigs that are showing clinical signs of early disease progression.

    It is rarely rewarding to submit tissues from pigs that have been dead for longer than 24 hours (and even less in hot weather), since postmortem changes will make the accuracy and effectiveness of diagnostics questionable.

  3. Inability to collect the right tissues.
    • Keep the work area clean to avoid contamination. While veterinarians or on-farm personnel usually do not have a dedicated area for posting pigs, a clean work area with good lighting (like outside the barn on the gravel or grass) is still helpful.

    • Your veterinarian will follow a routine collection order by starting with systemic tissues such as the heart, lungs, liver, spleen, kidney and lymph nodes/tonsils. Samples of the small intestine and colon will be collected last to avoid fecal contamination. Postmortem kits can be a convenient way to organize the supplies needed and serve as a reminder of which tissues to collect.

      After the organs have been removed, they should be individually packaged in whirl packs. If a clean surface is unavailable, each organ should be put directly into the whirl packs to avoid contamination.

    • It is important to collect enough of each organ to allow for multiple diagnostic tests. In general, a fist-sized piece should be adequate. With larger organs, such as the lung from larger pigs, there will be more volume of tissue than is needed. In this case, make sure to collect a sample of the abnormal-looking part of the lung — such as the part with pneumonic lesions — for lab analysis.

      Culture swabs can be used to sample fluid from swollen joints or other locations.

    • Formalin-fixed tissues from each organ are collected so that the pathologist can look at these tissues under the microscope for characteristic lesions caused by specific disease processes. This is referred to as histopathology.

    To prepare the fixed tissues, collect a thin slice of each organ (no more than 1 cm thick) and place it in a whirl pack, then add 10% formalin to “fix” or preserve these tissues. To adequately fix the tissue, at least a 3:1 ratio of formalin to tissue by volume is required.

    It is especially important to make sure the whirl pack containing formalin is adequately sealed by holding the tabs at the top of the pack and “whirling” the bag around at least six times, then folding over the tabs.

  4. Not properly storing and shipping tissues.

    After the pigs have been posted and the tissues processed, it is critical to refrigerate the sample packs until they are shipped to the lab to prevent additional decomposition.

    Tissue samples should be driven directly to the diagnostic laboratory or shipped “next day.” Every effort should be made to maintain a cool temperature without freezing the tissues. Gel packs can be frozen and used to keep the package cool during shipment. Diagnostic labs typically provide foam coolers and cardboard shipping boxes for this purpose.

    Tissues samples also must be sealed to prevent leakage and comply with shipping regulations. Packages that are leaking will not be delivered.

    The whirl packs containing the samples from each pig are packaged together in a one-gal. zip-lock bag, which is then packaged in a larger zip-lock container along with others, if there are tissues from multiple pigs. This larger zip-lock bag is then put into the diagnostic lab box that is lined with a garbage bag.

  5. Not taking precautions to prevent injury or infection.

    Some viral and bacterial diseases of swine are zoonotic (also having the potential to infect people). For this reason, it is important to take precautions by wearing latex gloves, boots and coveralls when posting pigs or handling tissues. Washing or showering after postmortem exams is also a good idea. Disinfectant wipes are an additional option for cleaning your hands and equipment where other options might not be available.

Use a sharp knife for the posting process. A sharp knife is much easier and safer to use than a dull knife, which forces the user to apply greater pressure to cut through tissues. A knife is obviously a potential cause of injury. When you combine a cut with infectious organisms, the risk can be compounded. Use common sense to avoid injury.


Posting pigs and processing tissues for laboratory diagnostics can seem intimidating at first, but with guidance from your veterinarian, this information can provide valuable information.

When mortality rate becomes a concern, it is important to quickly identify groups of high-risk pigs and identify the right pigs to post and collect samples for the laboratory. From there, it is just a matter of keeping things clean, and safely following a systematic approach to collect the right tissues, package them properly, and ship them off to the diagnostic laboratory.

Market Study Under a Microscope

In the Feb. 22 edition of North American Market Preview, I addressed the findings of the recently released Livestock and Meat Marketing Study by USDA's Grain Inspection, Packers and Stockyards Administration (GIPSA). The report has been a topic of widespread discussion since its release, but a number of those discussions have misinterpreted the results.

A perfect example came up in a discussion with University of Missouri agricultural economist Ron Plain earlier this week. Both Ron and I believe it is important enough to warrant attention in this week's column.

One of the findings highlighted in the study's executive summary was this:

". . . the estimated elasticities of industry-derived demand indicate a 1% increase in contract hog quantities causes the spot market price to decrease by 0.88%, and a 1% increase in packer-owned hog quantities causes the spot market price to decrease by 0.28%."

As background, an elasticity is a measure of the responsiveness of one economic variable to a change in another variable. Elasticities are expressed as percentages in order to remove the effect of the units of measurement (i.e. data using pounds has bigger numbers than data using tons).

These measures say that if the number of contracted hogs or packer-owned hogs changes by 1%, the spot market price will move 0.88% and 0.28%, respectively, in the opposite direction.

Some have interpreted that to mean: "If we reduce the proportion of hogs sold under contracts by 1%, we will increase spot market prices by 0.88%." Or, similarly, "If we reduce the proportion of hogs owned by packers by 1%, spot market prices will increase by 0.28%." By that logic, if we just eliminate the 25% or so of hogs owned by packers, we will increase spot market prices by 0.25 x 0.28 = 0.07 or 7%. Better yet, if we just outlaw the contracts used to sell 60-65% of all hogs, we would increase prices by 0.60 x 0.88 = 0.528 or nearly 53%. Wouldn't that be great?

But those numbers are wrong. The research does not address changing the proportion of hogs sold under these arrangements. It used the number of hogs sold through the various methods. So, a change in the number of hogs sold under contracts would affect the total supply of hogs. No wonder the effect is negative -- it is a demand elasticity that measures the change in total quantity on price.

In addition, each elasticity applies only to the amount of hogs sold under those methods. So, a 1% change in the number of hogs sold under marketing contracts is 1% of roughly 60% or 0.6% of the total supply. Similarly, a 1% change in the number of hogs owned by packers amounts to 1% of about 25% = 0.25% of total supply.

GIPSA's data indicated that, for the study period of October 2002 through March 2005, 59% of hogs were sold through contracts, 11% were sold through negotiated trades, and 30% of hogs were packer-owned. Given these shares, the correct way to use the estimated elasticities is:

  1. Contract supplies. A 1% change in the number of hogs sold under contract would amount to a 0.59% change in total supply and that change in supply would be associated with a 0.88% price change in the opposite direction. The price flexibility for total supply would be -0.88/0.59 = -1.49. Meaning that prices move 1.49% for each 1% change in total supply, if the change is sold through contracts.

  2. Spot market hogs. GIPSA found that the price elasticity with respect to spot market supplies was -0.27. A 1% change in the number of spot market hogs would amount to .01 x .11 = .0011 or 0.11% change in total supply. The price flexibility for that change in total supply would be -0.27/0.11 = -2.45. Each 1% change in total supply drives prices 2.45% in the opposite direction, if the change is sold in spot markets.

  3. Packer-owned hogs. The price elasticity with respect to packer-owned pigs was 0.28. A 1% change in the number of packer-owned pigs would amount to 0.01 x 0.30 = 0.3% change in total hog supply. The price flexibility for that change would be -0.28/0.3 = -0.923. That is, each 1% change in the total supply drives prices 0.92% in the opposite direction, if the change is comprised of packer-owned hogs.

Those impacts are dramatically different than the raw numbers. In fact, packer-owned pigs have the smallest impact on spot market prices and spot-market-sold pigs have the largest. If you think about it for a moment, that makes sense. Wouldn't the pigs sold at the price being measured have the biggest impact?

Whether you like these numbers or not, we need to use them according to how they were derived and what they actually mean -- not according to what we want them to mean. In addition, we need to remember that these numbers are only accurate near the level at which they were estimated. Doubling the number of hogs sold under spot markets would not have a -0.27% impact for each 1%. The -0.27 only applies near the number of hogs that represent the 11% market share in the data set.

None of this means this study is perfect. It is not. The huge amount of data and vast variation in the way producers and packers provided data appears to have caused some problems. But let's take time to make sure we are using the numbers correctly and, if need be, take another look at the data and the research methods and improve on them.

Click to view graphs.

Steve R. Meyer, Ph.D.
Paragon Economics, Inc.

Studying the Weight Class Swings

In my Hogs and Pigs Report review sent earlier this week, I alluded to the big swing between the year-over-year change between the inventory of 120-179 lb. pigs (-0.1%) and the inventory of pigs weighing over 180 lb. (+3.8%). That 3.9% total change between successive inventory groups struck me as very large and I questioned whether our industry, with its "constant throughput" goals, would actually see that much variation. So I went back to the historical data to see just where these numbers fit.

Figure 1 shows year-over-year changes in the inventories of pigs of different weights. This graph compares one quarter's under-60 lb. inventories, for instance, to the under-60 lb. inventory for the same quarter one year before. Data for the four weight classes are included. A few conclusions can be drawn:

  • As with virtually every other measure of production in the U.S. pork sector, this one demonstrates a decreasing level of variation. Annual swings of 20% were common prior to 1980, and 10% swings persisted even through 1998-99. The largest year-over-year changes this decade have been just 4%, and even those swings appear to be a thing of the past.

  • The weight categories generally lead one another in a quite logical fashion. While the graph is pretty busy, the blue line representing under-60 lb. inventories always moves first and then is followed by the heavier inventories.

  • The magnitude of the percentage inventory changes are very close, but recent changes in the heaviest category appear to be getting larger than the changes in the lighter inventories.

That last finding was rather curious, so I computed the differences in percentage changes for successive weight classes in the same quarter. For instance, I compared the percent change in the under-60 lb. category to the percent change in the 120-179 lb. category for the same quarter. Comparing weight classes this way should capture the cumulative effect of changes in pig crops and survival for previous time periods. I expected to see these numbers get smaller over time.

One potentially confounding factor, though, is imports of weaner and feeder pigs from Canada. Their dramatic growth since 2000 would suggest that negative class-to-class shifts should be less frequent and positive shifts may be larger.

Figure 2 shows the frequency counts for changes of 3% or more for each pair of successive weight categories. As expected, the number of changes of 3% or more, regardless of direction, has declined dramatically over the years. But the frequency decline for the difference in the top two weight categories (i.e. 120-179 vs. 180+ line) has been much smaller than for the lighter weight categories.

The second portion of Figure 2 shows the frequencies of declines of 3% or more between the weight categories. These, too, have fallen over time due to the relative stability of today's high-investment production systems and the fact that our industry has generally been growing. But note that the decline in frequency is less for the 180 lb. and over category than for the lighter-weight categories.

More to Learn
So is there any lesson to be drawn here? I think so. Year-to-year and group-to-group variation in the U.S. pig supply is definitely smaller than it once was. That comes as no surprise. However, changes of 3% or more in the year-over-year shift in weight classes are still not rare, especially for the 120-179 lb. vs. 180+ categories.

I'm still a bit concerned about the shift from +3.8% to -0.1% for the two numbers in last week's report. Much of that concern, though, lies in the fact that porcine circovirus-associated disease (PCVAD) was causing widespread death losses and that porcine circovirus vaccine is now on the scene.

We shouldn't expect the decline in slaughter in mid-April to be as abrupt as the report suggests but, if those numbers are correct, slaughter totals should begin a pretty sharp decline soon. Federally inspected slaughter through Thursday was 1.4% lower than last week, but that's a far cry from 3.9%.

Click to view graphs.

Steve R. Meyer, Ph.D.
Paragon Economics, Inc.

Veterinarians Oppose Swine Fever Rule

The American Association of Swine Veterinarians (AASV) has submitted comments to the U.S. Department of Agriculture (USDA) regarding recently proposed amendments to regulations governing the importation of uncooked pork and pork products from regions of Mexico positive for classical swine fever (CSF).

USDA’s Animal and Plant Health Inspection Service has proposed changing the import rule to allow for the importation of uncooked pork from CSF-free regions. Pork imports would have to be further processed in regions where CSF is known to exist.

Current regulations allow for uncooked pork and pork products to be imported only from CSF-free regions.

In its comments, the AASV opposed the proposal as presented due to the lack of a thorough risk assessment, estimating both the additional risk posed to the health of the U.S. swine herd and the overall benefit afforded the industry.

ASV also suggested additional safeguards should be enacted to ensure the product is not exposed to CSF virus during processing or transport. One such safeguard involves establishing a protocol for product testing to verify the absence of CSF prior to distribution.