While rational antibiotic use remains an important part of pork production, and is likely to remain so, there are a number of management alternatives that can reduce the need for their use. These management practices also minimize the introduction and spread of disease organisms, including potential food contaminants.
Biosecurity Practices The best alternative to treating disease is to prevent it. Biosecurity systems are put in place to prevent introduction of disease organisms onto a farm and reduce the spread of disease organisms that are already present.
Biosecurity programs should address the potential for introducing disease-causing organisms onto the farm from pigs, trucks, equipment, wildlife and people. A perimeter fence will help with all these areas of concern.
In addition, animal load out areas deserve special consideration. They should be covered and designed so as to prevent the return of loaded animals from the truck back into the premises. Only those trucks that have been properly cleaned and dried should be allowed to approach the load out area. Likewise, passages between buildings should be covered, bird-screened and any curtain-sided buildings should have bird screening in place.
Moreover, the most important aspect of biosecurity is to understand the health status of the source herd providing new breeding stock. The recipient herd and the source herd veterinarians should openly consult with each other to best accomplish this understanding. Breeding stock suppliers must be open with health status information. Their veterinarian should provide the results of diagnostic workups, slaughter checks, recent clinical observations and serological surveillance to your veterinarian.
When you and your veterinarian are satisfied with the health status of the supplier's herd, then set up an isolation/acclimation (I/A) program for the new breeding stock. Standard practices vary widely within the industry. Still, some general measures should be considered. It doesn't take long distances to separate the isolation facility from the farm. But the isolation area should provide for separation of air space and personnel. Animals in isolation can be cared for at the end of the work day by employees who won't re-enter the production facilities that day.
There are two reasons for the initial isolation period. First is to protect the farm from any pathogens the isolated animals may be carrying. Second is to observe the isolated animals for a certain period of time in case any outbreaks occur on the source farm after the animals have been delivered. A common isolation period is 30 days.
The next step in the I/A program is acclimation of the new animals. This involves exposing new stock to pathogens common to the home farm. This allows new animals time to develop an immune response to those pathogens. This exposure may include the use of vaccines, exposure to cull sows or "spent" gilts (females that have been added to the herd but have not conceived), or the feedback of manure.
When animals are delivered from two different source farms, as may be the case when both boars and gilts are delivered, the acclimation period allows them to become acclimated to each other as well. A normal acclimation period runs from 21-30 days. A combined isolation-acclimation period will take 60 days or more.
Movement Technology The biggest breakthrough in disease prevention and control didn't come from biotechnology or the development of new antibiotics - but from the widespread use of some common hog movement practices.
Herd Repopulations: In the past, "depopulation/repopulation" was the most reliable method of eliminating disease organisms from a herd. Other movement methods, discussed later in this paper, have largely replaced herd repopulations due to their relative lack of downtime and less dramatic disruption of cash flow. Herd repopulations are still useful in some situations and if planned correctly, can minimize downtime.
Herd repopulations used to be a popular solution when an unmanageable level of disease organisms had built up in a herd over time. My general advice was to consider repopulation when an operation was not competitive, and when problems exceeded solutions. In other words, repopulation was the method of choice if your herd had excessive, multiple disease problems.
Today, I see herd repopulations in a different light. Repopulation is a tool used in more specific situations, such as a herd wishing to get rid of one or more major pathogens, particularly in breeding stock herds. By using an off-site breeding project, actual nonproductive downtime can be two weeks or less. Downtime will likely be more in a one-site farm.
Partial Depopulation or Phase Depopulation: This is a form of depopulation that is tried in only one phase of production in order to clean up or cut down on the effects of a specific disease, such as endemic transmissible gastroenteritis (TGE) or porcine reproductive and respiratory syndrome (PRRS). It's most common to depopulate the nursery phase, but this technology may be applied to the finishing phase as well.
Before partial or phase depopulation is tried, however, some background work needs to be done. Diagnostic testing should be performed in the breeding herd, the nursery and the finisher to determine level of infection and how and when disease transmission is occurring.
The next step is phase depopulation. Sell feeder pigs or move them to another facility. It may be necessary to wean pigs into another facility for a designated period, depending on the organism being targeted. During the downtime, the phase that is being depopulated is cleaned thoroughly and disinfected. The objective is to break the cycle of transmission of an organism from older to younger pigs.
All-Out Production Systems: Commonly referred to as all-in, all-out production (AIAO), the key element of this technology is complete emptying of a room, building or site, and thorough cleaning before a new group of pigs enters the area. It is a planned, scheduled depopulation on a regular basis. An integral part of the process is washing and disinfecting.
Multi-Site, Isowean Production Systems: In this system of production, pigs are weaned into isolated nurseries or nursery-finishing buildings, thus the term "Isowean" as coined by D.L. "Hank" Harris, DVM, in the late 1980s. The purpose of Isowean production systems is to eliminate infectious agents and to enhance growth and lean tissue deposition. Specifics of the system, including recommended weaning age, may vary on the organisms targeted for elimination or reduction.
But the general principles are the same - move young pigs away from the sow herd so that diseases that affect grow-finish performance are not transferred within the same facilities to susceptible pigs by older pigs or by people. If disease organisms are introduced onto a site, multi-site production offers more flexibility than traditional systems for dealing with the problem. Sites can be depopulated as described earlier, using partial or phase depopulation, without the need to depopulate the sow herd.
Reproductive Technology There is currently one, production-based reproductive technology, artificial insemination (AI), that is being successfully applied to improve pig health and potentially decrease the need for antibiotics. The use of AI as a health strategy was discussed in detail in the April 15, 1997 Blueprint Series, "The Art of AI."
In brief, AI provides these pluses:
It reduces the number of animals brought onto the farm, and
Females aren't exposed to the natural mating process, allowing a more hygienic process if AI is carried out correctly. In some farms, vaginal discharges have declined when AI replaced natural mating.
A second reproductive method that's not readily available, but will allow movement of genetic material with greatly reduced disease risk, is embryo transfer. It is possible to wash embryos after collection, potentially improving health status above that attainable by AI. This technology will be widely used when practical, non-surgical collection and transfer methods become available.
Environmental Modifications Several environmental changes will reduce the need for antibiotics. Start with a good cleaning and sanitation program, together with AIAO production. The keys are removal of manure and all other biological residues with hot water power washing. Follow cleaning with one of many available disinfectants. Scheduled washing in facilities that are not usually run AIAO may be useful as well.
The best medicine for vaginal discharge complex is power washing the breeding/gestation building every 2-4 weeks or washing the area as groups move to farrowing.
A second environmental modification could be to alter stocking density. My observations are that 8 sq. ft./pig is a good starting point, but should be altered to account for the type of flooring, the waste removal system and the disease organism.
For high-health pigs in an environment with good waste removal, good air quality and little disease challenge, something less than 8 sq. ft./pig may be the best stocking density. With a heavy disease challenge or the presence of certain serious organisms, for example Actinobacillus pleuropneumonia, a lower stocking density is advisable.
A third environmental modification related to stocking density is adjustment in group size. As with stocking density, the optimum group size isn't known and likely varies with the type of facility. However, when faced with serious disease threats, decreasing group size may help. Some farms are having good results with large pen/large group systems, but there is little controlled data available.
Finally, providing the proper environment for the pigs will decrease the need for antibiotic use. Major considerations are effective environmental temperature (EET) and lower critical temperature (LCT).
EET is the temperature the pig feels. LCT is the temperature at which the pig must increase its heat production rate, usually by increasing feed intake, to maintain body temperature. LCT varies with pig age and with group vs. individual housing. Pigs maintained at an EET lower than the LCT will be more susceptible to the effects of endemic pathogens and, therefore, more likely to show clinical signs of respiratory or enteric diseases. Additionally, air quality must be maintained in order to reduce pig exposure to airborne bacteria, dust particles and gases.
Diet & Health Interactions The interaction of diet and health is much broader and more complex than deficiencies or excesses of specific nutrients. Nutritionists now recommend specific, daily nutrient intakes based on age, sex, season and genotype. These suggestions must be considered when evaluating disease treatment and prevention measures.
Poor diets can increase susceptibility to disease. But the converse is also true. Diseases alter feed intake (respiratory diseases) and nutrient utilization (enteric diseases), thereby predisposing pigs to other metabolic or infectious diseases.
An example is the pneumonia/ulcer complex. Ulcers are often found in conjunction with pneumonia, probably stimulated by the decrease in feed intake often seen with respiratory disease. In addition to the factors mentioned above (age, sex, season and genotype) it may become more common to consider disease load and immune status when formulating diets. These types of diets may decrease the need for antibiotic use.
Stimulating Immunity The most common ways to stimulate the immune system are to inject vaccines, to expose naive animals to sick or carrier animals and to provide feedback of manure or other biological material (mummies or placenta for parvovirus exposure or intestinal contents for TGE exposure). The goal is to boost immune response to specific diseases prior to exposure. Vaccines and other types of exposure have been used for many years with variable results.
Keep in mind these vaccination tips when attempting to provide immunity for disease prevention:
Vaccination does not always equal immunization. Vaccines and other types of controlled exposure fail for a number of reasons: the animal may have been incubating the disease at the time of vaccination; the animal may already be sick or stressed and unable to respond to the vaccine; or exposure may overwhelm the animal's defenses.
Also, the vaccine may be unable to stimulate immunity against the disease in question. Some vaccination tips:
Vaccines stimulate the immune system; they do not eliminate disease organisms.
Proper vaccination timing is critical to success. The vaccine should be given soon enough before exposure to a disease challenge to allow the animals' immune system to respond. Usually this should be done at least two weeks prior to exposure. Also, many vaccines require two injections, 2-3 weeks apart, in order to stimulate protective immunity.
Genetic Resistance In the future, genetic resistance to hog diseases may be an option to conventional disease control strategies. There have been reports of genetic differences in susceptibility to atrophic rhinitis, respiratory diseases, porcine reproductive and respiratory syndrome, and colibacillosis.
Progress in selection for genetic disease resistance has been slow due to the necessity of selecting for other performance traits (growth, leanness) that may be counterproductive to selecting for disease resistance.
In addition, selection under field conditions introduces many confounders (environment, management systems) to the process. The use of molecular genetic techniques to find genetic markers or the actual genes linked to disease resistance will potentially allow greater progress in this area in the future.
Strategic Medication Strategic medication involves the use of antibiotics at precisely defined times for a well-defined purpose. Often, injectable, water or feed medication will be used just before the anticipated exposure. If the exposure times or stress periods can be defined well enough, this approach can be useful.
Examples of strategic medication include the use of water medication prior to nursery pig exposure to strep organisms, specific injections in a medicated early weaning (MEW) program, the use of antibiotics in an isolation diet for prevention of ileitis, or spot treatment with an antibiotic for chronic urinary tract disease in gestating sows.
Often, the problem with strategic medication programs is that what starts out as strategic becomes routine. The challenge is to use medications wisely and as needed. The economics of production and quality assurance considerations dictate as much.
Summary There are many viable, production-based, management alternatives to the use of antibiotics in pork production. Most of them are available for your use today. Some would require production system changes (i.e., the movement technologies). Some will be applied in the future (i.e., embryo transfer, genetic resistance). None are likely to replace the need for rational use of antibiotics. But, by using the available alternatives when possible, antibiotics can be used less frequently and more effectively.