Changes in the health of finishing pigs have been impacted by a variety of industry changes.
Finishing health has been defined many different ways, but most agree that the first 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.
Of course, there were some bad bugs in those days that would escalate death loss. Actinobacillus pleuropneumonia (APP), for example, was known to wreak havoc, and could cause mortality rates to soar into double digits. Now severe APP outbreaks are rare.
Changes in the health of finishing pigs have been impacted over the years by a variety of industry changes in genetics, nutrition, environment, weaning age, pig flows, group size, stocking density, market weights, biosecurity practices, diagnostic tests, backfat, percent lean, vaccines and antibiotics.
Of course, the real changes that have taken place have been in the diseases we fight. We've added totally new diseases to North American pork production, such as porcine reproductive and respiratory syndrome (PRRS) and porcine circovirus-associated disease (PCVAD), which were unheard of 20 years ago.
The reason mortality rates are higher, in some cases much higher than 20 years ago, is because rarely does it turn out that disease outbreaks are caused by a single disease entity.
Over time, we've created healthier, leaner, faster-growing, larger groups of pigs that have mostly come from healthier sow farms than ever before. To use a sports car analogy, we are now feeding Porsches and Lamborghinis vs. the Fords and Chevys of the past.
Not only do these pigs require premium fuel, they are also more sensitive. You had better “baby” these high-performance models or they will break down and leave you stranded!
In short, today's pigs are less likely to have been exposed to bugs that we considered normal flora years ago, and thus are more prone to get sick if infected.
These pigs leave the nursery without having had an opportunity to build immunity. Since they are often considered high health, they enter the finisher without being vaccinated and so are vulnerable to disease challenges.
Of course, there are other ways to define health than merely an increase in mortality. Health affects performance, namely average daily gain, feed conversion, days to market and the number of culls or undervalued pigs.
While none of these performance parameters alone are indicative of health issues, together they may point to a health challenge in spite of low mortality.
Industry standards, targets and benchmarks provide a good place to begin a comparison. But they do not take into account differences or idiosyncrasies of a particular farm or system.
Use farm-specific records to analyze the effects of disease and the value of health. Records are vital to differentiate between groups of pigs, caretakers, sites, seasons and genetics.
Steps to Healthy Finishers
Regardless of current health status, follow these three basic steps to reduce health problems in the finisher:
Determine what disease organisms or health issues exist within the population (diagnose).
Provide appropriate therapy and supportive care for pigs that are clinically ill (treat), and
Design a preventative program to keep the problem from reoccurring (prevent).
Most experienced pig caretakers intuitively perform these three steps every day as they go about their daily barn walks. Lets take a closer look at these three vital steps:
Step 1: Diagnose
The first step to good health with any group of pigs begins the day of arrival and should continue at least daily through the entire finishing phase.
Daily observation is required to identify early signs of disease or injury. The good caregiver will perform this observation on three levels: the barn, the pen and the pig.
At the barn level, the producer ensures that environmental conditions are in balance.
At the pen level, common disease signs to look for may be as simple as hearing a cough somewhere within the pen or observing diarrheic feces on the floor. These signs can be clues to help find individual pigs with problems.
At the pig level, determine if a pig is normal or abnormal. If deemed abnormal (sick or injured), then the problem needs to be classified as to its nature or to what system (nervous system, respiratory system, etc.) is affected.
Remember that diseases can be clinical or subclinical. Clinical disease is where signs of illness are evident. For subclinical disease, the illness may be very early in its course, and has yet to produce the typical, full-blown symptoms that would be obvious to even the casual observer.
Keys to disease resolution are early detection and subsequent proper treatment.
Observation and treatment varies with the production stage, size and number of pigs requiring individual attention. For a 1,000-head finishing barn with conventional-sized pens, it should take an experienced caregiver 30 to 45 minutes to individually observe and treat 10 pigs.
As a proper incentive to identify every pig needing attention, it is a good practice to attempt to identify at least 1% of the pigs in any given barn or room as those that need some form of attention.
Even in what may appear to be a healthy, normal barn of 1,000 pigs, there will nearly always be at least 10 pigs that could be deemed “abnormal” each day. Setting this as a daily, personal goal will provide a proactive course for maintaining health.
Good chores and observation of every pig, every day and acting on these observations will lead to proactive behavior of the caregiver. Being proactive will lead to good pig health.
Often the most valuable animal in the barn is the first one to die! That is only true, however, 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 on the cause of death, not only because of their training, but most importantly, because their experience enables them to recognize what is normal and what is abnormal.
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 they should be ready to ask questions.
Producers should 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 when a health challenge occurs.
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.
Serologic testing, performed on live pigs to check for health status, can be a valuable diagnostic tool. A blood sample is easily obtained, and there are many tests that can be run on the serum or blood of a pig.
Some serological tests, such as enzyme-linked immunosorbent assay (ELISA), measure a pig's immune response to a disease challenge. But it can take several weeks for the pig's immune system to mount a response to a disease before it would be detectable in the serum.
Other tests, such as polymerase chain reaction (PCR), detect the presence of some of the common viruses in the blood, such as the PRRS virus.
Both types of tests can provide valuable insight into a population's disease status. But because of their complex nature, always consult your veterinarian for help with diagnostic goals and interpretation of results.
If used alone and interpreted improperly, serology may lead to faulty health assumptions. Always consider serology (and other diagnostic tools) in the proper perspective, and know that they merely provide pieces of the larger health picture. Factors such as clinical signs of disease and history of the population must also be considered.
After determining health status, assign a classification of the diagnosis. It is best to keep this process as simple as possible, such as grouping by the dominant clinical symptom.
A simple system would be to classify the abnormal pigs into three primary groups — respiratory (lungs); enteric (gut); and other (lame, injury, etc.). You can't always wait for lab results before starting treatment, so this simple classification system will aid in choosing the initial treatments.
Step 2: Treatment
Once a preliminary diagnosis has been made, choose the therapy that best addresses the health concern diagnosed. At the same time, if underlying problems were discovered during the observation phase, it is imperative to correct these issues before starting treatment.
Before initiating any treatment protocol, besides determining the preliminary diagnosis, the caregiver must first consider many other factors:
How many pigs in the barn are showing the same clinical signs?
How fast was the onset of clinical signs?
If left untreated, would pigs die?
Are the clinical signs primarily respiratory or enteric?
How close is the group to market? Is withdrawal period a concern?
How much time is available for treatment and followup?
What is the health history of prior groups?
Are there obvious underlying problems that could have triggered this event?
Based on the answers to these questions, the caregiver will determine the type and route of the treatment that best fits the health issues occurring in the barn.
A respiratory health challenge will likely require a different treatment regimen than an enteric problem.
A challenge that suddenly affects the entire barn may require the use of mass medication via feed or water.
Some veterinarians promote the concept of “trigger” levels of affected animals required to initiate mass medication of any kind. This “trigger” level may be 3-5% or higher, depending on the situation.
There are a number of educational tools to aid in choosing the right medications. Always work with your veterinarian to set up treatment protocols that can aid in the decision-making process. Veterinarians are knowledgeable in prescribing the proper medicine at the proper dosage, route and withdrawal periods. They are also familiar with withdrawal periods and potential interactions and contra-indications that may exist with a particular set of pigs.
Your veterinarian can apply the “Judicious Antimicrobial Use Principles for Swine Veterinarians” through the normal course of his or her practice. These principles and guidelines were developed in cooperation with the American Association of Swine Veterinarians, the American Veterinary Medical Association and the Food and Drug Administration's Center for Veterinary Medicine to aid in the proper use of antimicrobials and the reduction of antibiotic resistance.
The National Pork Board's Pork Quality Assurance Level III and Take Care — Use Antibiotics Responsibly programs are excellent educational initiatives that promote proper swine care through “good production practices.” Everyone responsible for the day-to-day care of pigs should be familiar with and implement these principles and practices.
The final step with any treatment protocol is to evaluate its success and be ready to change the course of therapy if the pigs do not respond positively. A lack of response may be due to one of two factors: either an inaccurate disease diagnosis, or antibiotic sensitivity testing may reveal that the diagnosis was correct, but the choice of treatment medication was inadequate for this particular case.
For example, in a case of an uncomplicated viral infection, such as swine influenza virus (SIV) or porcine circovirus, you would not expect antibiotic therapy to be successful because antibiotics don't work against viral agents.
Evaluation of success or failure of treatment also requires good records. Document which pigs were treated and by whom, the medications administered, dosage, route, duration of treatment and the expected withdrawal period, results and the prescribing veterinarian in cases of extra-label drug use.
Evaluation of the treatment choice is also important for future decisions on preventative programs. If treatment success is limited (as with uncomplicated viral infections), then the focus should be turned to the final step in our approach to health issues in the finishing phase — prevention.
Step 3: Prevention
Disease can occur when pigs are exposed to an infectious agent in dosages sufficient to overcome the pigs' immunity level. Often, infectious agents can be present without causing disease, because the immune system provides adequate protection.
On the other hand, the infectious dose (the dose required to cause disease) may be quite low if the pig has little or no immunity to that disease agent.
Pigs can only express clinical disease when their immune systems don't provide adequate protection to a given amount of exposure. Stress of any kind, but especially environmental stressors such as extreme temperature swings, drafts or overcrowding, reduce the pig's ability to ward off a disease challenge.
The pig's immune system produces antibodies against infectious agents such as bacteria, viruses and even some parasites. Antibodies are proteins produced by the immune system in response to exposure from either the actual disease agent, or a vaccine made from such a disease agent. This type of immunity is called “active” immunity as opposed to “passive” immunity, which the pigs receive from their mother's milk via colostrum shortly after birth (See Figure 1 on page 18).
Pigs are born with little or no immunity, so it is very important for them to receive this passive immunity from the sow in order to provide protection until their immune systems mature and provide active immunity.
By the time the pig reaches the finishing phase of its life, most or all of the passive immunity has waned. The pig has begun to develop its own active immunity in response to exposure to bugs in its environment or to vaccines administered in the nursery phase.
In some instances, the presence of passive immunity actually blocks the pig's own system from producing active immunity. This is called “passive antibody interference,” and with certain disease agents such as SIV, it can last until the pig is well into the nursery or early grower phase (40-80 lb.).
The principle of passive antibody interference, coupled with the age at which pigs are first exposed to the disease agent, are paramount in deciding the age at which vaccination efficacy is optimized. Most vaccines need to be administered two to four weeks ahead of the anticipated disease challenge or exposure to the infectious agent.
Other factors to consider for preventive treatment effectiveness include the type of vaccine used; the health and nutritional status of the pigs at the time of vaccination; the presence of environmental stressors; and, with some of the newer modified-live-virus vaccines, whether the pigs are currently being treated with antibiotics.
It is important to remember that vaccines rarely confer 100% protection against any given disease. As you might imagine, there are multiple pitfalls that can occur along the path to producing a protective immunity in the pigs besides proper timing of vaccination. In addition, some vaccines are better than others at overcoming these pitfalls.
As with any animal population, we must never forget the normal variation that exists within any group or flow of pigs. Population dynamics interact with this biological variation to produce the normal distribution of whatever trait you may wish to measure.
This normal variation within a population accounts for the fact that while the average pig in the group may be well protected from a disease challenge with the vaccination, a small percentage of the group fails to mount an adequate response.
If a few pigs in the group develop clinical signs of the disease after being vaccinated, it does not necessarily mean that the vaccine failed across the population. Normally, for every pig in a group that failed to mount a protective immunity, there was also a pig that produced much more immunity than was needed for protection.
Development of a vaccination protocol and schedule requires that you first know what health challenges exist in the population, and an estimate of the economic effect they make on production. A working knowledge of the available immune management tools, as well as the approximate cost of vaccination, is required to estimate the cost: benefit ratio of any given program. Rely on your veterinarian to drive adoption of any vaccination protocol in your herd.
The ultimate tool for disease prevention is to never allow the introduction of new infectious agents. The finishing phase of most operations is often considered to be at the bottom of the health pyramid, and thus, the safeguards are fewer and less stringent than at the sow sites and nurseries.
The primary objective of any biosecurity protocol is to prevent the entry of new bugs, regardless of the stage of production.
While location of the site and proximity to other pigs are important biosecurity risks, there is usually little that can be done on these issues once a barn is sited.
We can, however, work to reduce the risk associated with many other practices, vectors and fomites that present biosecurity challenges.
If you are bringing in healthy pigs with good protective immunity, it just makes good sense to enforce similar biosecurity protocols and take similar precautions as you would in the sow sites or nurseries that supply the pigs.
Porcine Circovirus-Associated Disease: Emerging Threat to Grow-Finish Health
The U.S. swine industry is experiencing an emerging health challenge the likes of which haven't been seen since the early years of porcine reproductive and respiratory syndrome (PRRS).
This “new” syndrome was originally named postweaning multi-systemic wasting syndrome (PMWS), to reflect the wasting condition that characterizes this disease.
Recently, scientists and swine practitioners have coined a new term for this problem: porcine circovirus-associated disease or PCVAD. This name reflects growing evidence that porcine circovirus type 2 (PCV2) is the primary player in this disease complex.
PCVAD is a growing problem and generally hasn't affected pigs until they reached the grower stage of production.
There is no doubt that concurrent infections or stressors may make this disease worse, especially PRRS virus, swine influenza virus, Mycoplasmal pneumonia and Salmonella cholerasuis.
Disease Severity Grows
Circovirus and clinical signs of wasting have been present in U.S. swine herds since the late 1990s.
But a new, more severe form of the disease has been reported in eastern Canada since late 2004, and has gradually spread to the United States in 2005 and 2006.
These more severe clinical signs may be associated with a new or altered strain of the disease. This strain causes mortality rates to double in late nursery, but more often in early finisher flows. In a few cases, mortality rates have topped 40%.
Adding to the confusion surrounding PCVAD is the fact that porcine circovirus has existed on most hog farms in North America for many years without causing noticeable problems.
If you suspect PCVAD has infected a group of pigs, first contact your veterinarian to obtain an accurate diagnosis. Other pathogens and syndromes can produce similar clinical signs.
Essential for a confirmed diagnosis is the presence of clinical signs producing substantial mortality, plus laboratory confirmation of microscopic lesions and the presence of PCV2 in the tissues.
Besides animals off feed and experiencing very rapid weight loss, the other most common clinical observation is a respiratory problem such as thumping and labored breathing.
After confirmation of PCVAD, your veterinarian can outline management changes to reduce disease severity and prevention steps, which may include vaccination.
It may be necessary to identify and control any concurrent infections such as PRRS, mycoplasma, SIV or salmonella.
Implement management changes to reduce disease severity. Strictly adhere to all-in, all-out (AIAO) pig flow, avoid mixing and resorting of animals, reduce stocking density and take steps to improve the environment.
Good hygiene and disinfection of facilities are also essential to minimizing the impact.
Early removal of the affected pigs from the group or site appears to have helped reduce mortality in some cases.
The most encouraging news regarding PCVAD is that there are several commercial vaccines under development. Early field reports indicate they appear to be very effective when administered to weaned pigs ahead of the expected disease challenge.
Many aspects of this disease remain unknown, any one of which could help control the spread and reduce the economic severity of PCVAD.
Make Treatment Chores Convenient
Daily health checks and chores can be simplified if you can take all of your supplies with you during the walk-through.
For example, a fly fishing vest is lightweight, durable and has numerous pockets and places to safely carry supplies and equipment.
If this vest saves one trip back to the office for a forgotten treatment medicine, etc., it eventually adds up to a lot of valuable time that is better spent diagnosing and treating pigs.
Be it a fishing vest or a customized tote tray, make sure you pack it with enough supplies and equipment to last the entire walk-through.
Some suggestions for what to always carry include:
An assortment of treatment medicines;
Syringes (disposable and otherwise);
Hypodermic needles (always use the correct gauge and length and never straighten a bent needle);
Marking crayon or spray (assorted colors);
Safety scalpel for castrations and other minor surgery procedures;
An inexpensive digital thermometer;
Pen and notepad; and
Basic tools such as locking pliers, an adjustable wrench and screwdrivers.
The more time spent with the pigs vs. walking back and forth for supplies and tools, the better the overall health of the pigs.