Most producers agree that the best way to deal with respiratory disease is prevention. But prevention often means vaccination or medication with little regard to the production practices that promote health.
Promoting health is a 24-hours-a-day, seven-days-per-week job, whereas disease prevention strategies are viewed as short-term activities, that are expected to yield outstanding results.
Unfortunately, the underlying biology of the pigs, the bugs and their association are not very forgiving. A short-term lapse in promoting health can have long-term consequences in the pig. Disease can occur within hours, days or weeks after the lapse.
Problems in the finisher actually start in the nursery or farrowing room. Our ability to understand when these lapses occur is hampered by how well we observe the pigs and their environment.
Numerous studies prove the impact of environment on respiratory disease. Yet objective evaluations of the environment are rarely part of a problem-solving strategy for respiratory disease.
Also, observations occur during the day, and we have no idea what happens at night.
Finally, the health of all pigs in the population needs to be promoted. For example, it is rare to find a nursery “comfort board” that is large enough to handle all the pigs in the pen.
The following production practices apply to pigs of all ages.
Provide effective environmental temperature (EET). This is influenced by air temperature, air velocity across the pig, floor (contact) temperatures, wall/ceiling (radiant) temperatures, moisture/humidity, zone heating and bedding. Accurate measurement of the individual parts holds the key to providing the proper EET.
Air temperature is easily measured by a standard thermometer, but temperature changes over time are often more important. High-low thermometers serve as useful monitoring tools. In barns with reoccurring problems, continuous-recording thermometers often reveal sudden temperature fluctuations that substantially contribute to the problem. Surface temperatures are best measured using an infrared thermometer.
Air velocity can be estimated by observing smoke movement patterns, but objective measurement of air speed requires an air flow meter.
Assessing EET is critical for diagnosing problems in suckling and nursery pigs that are prone to chilling because of their small body size. Pig behavior such as sleeping and dunging patterns will tell you if the EET is improper. But evaluate the components of EET in order to make the necessary adjustments.
Control gas levels. Gases of concern include water (humidity), oxygen, ammonia, carbon dioxide, carbon monoxide and, of course, hydrogen sulfide.
The ventilation system should be viewed as an extension of the pig's respiratory tract. The pig breathes in oxygenated air and exhales carbon dioxide-containing air.
Heaters use oxygen to burn fuel, producing carbon dioxide (clean burning) or carbon monoxide (incomplete combustion).
Ammonia is often used to evaluate gas levels because we can smell it. In my experience, ammonia is not a good indicator of ventilation quality because the levels can be greatly influenced by the waste handling system.
Measuring carbon dioxide levels provides a better indication of ventilation rates but requires specialized measuring devices. In the past two years, I've investigated several cases of poor nursery performance that were directly attributed to high carbon dioxide levels, even though ammonia and humidity levels were acceptable.
Gas levels are dependent on the ventilation rate and correct mixing of fresh air with stale air. With mechanical, negative pressure systems, I have yet to see a situation where the “20-foot rule” does not apply. The 20-foot rule states that wherever you are standing in a room, you should be no more than 20 feet from an inlet. Designs that fail to follow this rule either have dead spots or turbulence in the microenvironments where pigs live.
Proper stocking density is a controversial subject. Requirements for top production in one phase may be different than those for the next phase.
For example, inadequate space in the late nursery phase, which is commonly observed, can promote disease in the finisher. Stocking density also impacts feeder space and drinker availability. Stocking rates should be based on the space requirements of the pigs as they exit the production phase.
Ensure food and water availability. Food access is mostly a problem in the early nursery phase; the presentation of the diet can dramatically impact feed intake.
Failure to promote feed intake in small pigs by gruel feeding or using special diets creates a subpopulation of animals more susceptible to disease.
Water availability issues are mainly a challenge for the weaned pig. Regardless of age, pigs can suffer from an inadequate water supply. An important defense mechanism in the respiratory tract is the removal of debris and pathogens by the mucociliary escalator apparatus. Proper hydration of the animals is important for maintaining this apparatus.
Segregate pig flow (all-in, all-out production) by room, building or site depending on disease concerns. For viral diseases, site separation is often required, although some diseases can travel between sites. Building and room layout within continuous flow sites will also influence health status. Segregated production also implies that all aspects of the facilities are thoroughly cleaned and disinfected between batches of pigs.
Realize that operation (population) size influences the pattern of disease spread within a herd. Larger herds typically take longer to develop whole herd immunity and the dose of organisms can progressively increase as the disease spreads through the herd. Pig density also influences the effectiveness of the ventilation system. The bottom line is that large herds must make fewer mistakes.
Reduce vertical transmission from sows to pigs. This can be accomplished by reducing weaning ages, stabilizing the immune status of the breeding herd or by eliminating disease.
Store vaccines and medications for product effectiveness. Refrigerators should be monitored daily for temperature. High temperatures or freezing will ruin many products. Overstocking can result in poor air circulation and uneven temperatures within the refrigerator.
All vaccines and medications should be stored in a clean and dry environment. Attention should be paid to proper injection techniques, dosages and withdrawal times. Expired products should be discarded or returned to the supplier.
Address biosecurity needs externally and internally. Internally, design procedures for moving people, animals and equipment that reduce disease transmission within the herd.
External biosecurity is dependent on a number of issues, including purchased animals, animal transport vehicles and truck drivers, wild animals, proximity to other farms, repair personnel and their equipment and visitors.
Provide accurate and timely diagnostic testing to determine which disease is causing the problem. Diagnosis of a specific respiratory disease-causing agent is nearly impossible by simply observing the lung tissue during a postmortem examination. Follow-up laboratory testing is the only way to make this determination.
Promoting health through proper production practices holds the key to controlling respiratory disease.