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Prevention vs. Treatment of Disease

PRRS has taught us that sourcing quesitons begin at the conception of the source animal.

Our mothers and grandmothers knew the value of disease prevention after years of respiratory disease and diarrhea in children.

Likewise, the sharpest pork producers challenge their veterinarians to provide appropriate disease prevention plans and monitor their results.

Disease prevention or control begins with understanding what diseases and risks are present and extends to implementation and monitoring. Careful review of sources and health status lays the groundwork for the future.

Following a complete review of health status, control measures are necessary to limit the negative impact of known pathogens. Change must be deliberate and controlled to adequately monitor results. Performance of the growing pig is the ultimate indicator.

Source Screening is Critical

Whether selecting a gilt supplier for a breeding herd, or weaned pigs for the grow-finish system, understanding your source is critical. The simple “standard” disease-free checklist is not sufficient to make plans.

Questions for the gilt supplier need to include health status for diseases like pseudorabies, porcine reproductive and respiratory syndrome (PRRS), atrophic rhinitis, Actinobacillus pleuropneumonia, Transmissible gastroenteritis, mange and swine dysentery.

Review with your veterinarian how the source manages Streptococcus suis, Haemophilus parasuis, swine influenza virus (SIV), Mycoplasmal pneumonia and others.

PRRS has taught us that sourcing questions begin at the conception of the source animal. Development of the gilt prior to birth may impact her entire life in terms of disease status and immune development. History tells us we want fetal development of PRRS-negative gilts.

A PRRS-positive commercial sow herd needs to expose breeding gilts to their own strain of PRRS virus; however, they need a PRRS-negative source and they need to expose the replacement gilt to PRRS virus prior to 2 months of age.

The supplier of weaned pigs to the grow-finish population also must openly provide herd vaccination history, weaning age history, current health monitoring protocols and contact information for health changes.

First-time pig buyers should ask the source herd questions regarding farrowing crate number in relation to herd population, their gilt entry protocols, short-term and long-term health goals, and even plans in the event of a health break at either location (Table 1).

Successful long-term relationships depend on shared goals for the health of the entire system. Biosecurity is only part of this plan. Sow herd disease management and grow-finish health plans complement each other.

Breeding Herd

Incoming gilts and young-parity females entering the breeding herd are being recognized as major sources of diseased piglets. These animals pose an immediate challenge to sow herd stability and a greater challenge to the grow-finish population.

Few systems are large enough to segregate gilts and first-parity females onto separate sow sites. Systems with this edge believe grow-finish has the most to gain from segregation of piglets reared on those young females.

All sow herds must keep a consistent flow of replacements. Usually, weekly gilt entry leads to a modified, continuous-flow gilt development where multiple-aged gilts are raised near or even in the same finisher barn.

Maternal colostrum protection, weaning age, early vaccinations, and disease exposure help to create immunity in gilts less than 50 days old.

PRRS-positive commercial herds may take gilts from a known naïve PRRS source and expose them to PRRS to prepare them for entry. Immunologists tell us that cell-mediated protection requires four months without re-infection for complete PRRS virus control. An early exposed gilt could still have a changed PRRS virus with her sisters and bring new PRRS strains into the breeding herd.

Table 1. Questions for the New Weaned Pig Source
1. Current disease status of sow herd and sow herd source
2. Current monitoring program
3. Number of farrowing crates and sow herd inventory
4. Genetics of both male and female
5. Grow-finish closeout history
6. Weekly piglet production for last 26 weeks
7. Current sow herd vaccination program
8. Current piglet medication program
9. Source information for health break
10. Short-term and long-term health goals

Controlling PRRS

PRRS control measures deserve attention. Herds in the acute stages of a break have seen some benefit from killed virus vaccination to reduce shedding and shorten the activity period. This is likely valuable only if PRRS virus does not continue to evolve and mutate in the herd.

Other herds have stabilized using positive nursery pigs or even serum from actively positive groups to expose entire populations. The same rules must apply to be successful — exposure prior to 2 months of age, followed by four months of inactivity.

Immunologists also caution, don't create large numbers of PRRS virus populations through uncontrolled activity. At our clinic, we have attempted to sequence virus and serologically monitor every gilt group monthly to gain confidence regarding early exposure.

Eliminating PRRS

The elimination of the PRRS virus is a common topic of discussion now that many gilt suppliers have established PRRS-free herds. The risk of naïve entry poses another problem for the commercial producer.

Our clinic has helped many producers evaluate the cost benefit of off-site breeding with entry of PRRS-naïve gilts in late gestation (Table 2). Failures still occur as herds don't fully stabilize for PRRS and virus breaks back. Even so, the benefits of improved productivity and grow-finish performance make this alternative very attractive, even if the sow herd is only PRRS free for 12-16 months.

Other Gilt Programs

As bad as PRRS is, it's not the only preventable disease we manage in swine production. Gilt development programs must also include the more easily controlled organisms such as mycoplasma, SIV and ileitis. In later development, pre-breeding gilts also require parvovirus, leptospira (five strains), and erysipelas boosters with herd maintenance vaccination protocols for disease prevention.

Pre-breeding vaccines are often better if they follow a controlled feedback program in herds where segregated production may lead to naïve breeding stock. Feedback must be controlled due to the risk of creating uncontrolled PRRS viremia (presence of virus in the blood).

Table 2. PRRS Elimination Project (Herd Roll)
Current Production Post Elimination
Sow Herd Impact Analysis
Sow Herd Size 2,400 2,400
Litters/Sow/Yr 2.38 2.45
Pigs Born Alive/Sow 10.21 11
Preweaning Mortality 12% 9%
Pigs Weaned/Sow 8.98 10.01
Weaning Weight 10.5 10.5
Number Weaned 51,321 58,859
Weaned Pig Cost $33.82 $29.49
Annual Sow Farm Costs $1,735,682.23 $1,809,382.23 (production plus herd roll cost)
Herd Roll Cost
Breeding Project Cost (10 months)
Gilt Housing cost/gilt $30.00
Additional Breeding Costs/gilt $28.00
Additional Testing Costs/gilt $3.00
Additional Transport and Labor Costs/gilt $6.00
Total Herd Roll Cost $73,700.00*
Grow-Finish Impact Analysis
Nursery Medication Cost (all) $2.65 $1.65
Nursery Mortality 3% 2%
Finisher Medication Cost (all) $3.50 $2.50
Finisher Mortality 5% 3%
ADG (wean-to-finish) 1.45 1.55
Feed Effic (wean-to-finish) 3.00 2.75
Feed Cost/lb Gain (no meds) $0.185 $0.185
Slaughter Weight 265 265
Grow-Finish Space Cost $17.50 $17.50
Transport $2.00 $2.00
Number Sold 47,215 55,916
Cost of Production $106.55 $100.22
Cost of Production (cwt) $40.21 $37.82
Difference in Production from Disease Elimination $354,007.99
*The total of $67/gilt for 10 months of gilts on a 2,400-sow farm with a selection rate built in = $73,700.

PRRS-naive herds can collect small amounts of mummified fetuses, sow manure, placenta and piglet manure every week and provide this material to gilts in late development. Feedback must be discussed in a whole herd health program context and must be done for a specific reason (Table 3).

We have stopped using cull sow exposure due to inability to verify or quantify PRRS shedding in those females.

Likewise, we have not attempted tonsil scrapings to create an exposure material. Whatever exposure method is used for PRRS, stick to the rules of immunology — exposure prior to 2 months of age and four-month recovery without reexposure.

In sum, disease prevention begins with the sow herd. Quarterly monitoring may be sufficient for commercial production. Continual evaluation of efficacy of prevention measures lies with the quality of the weaned pigs.

Sow herds require, as a minimum, routine vaccination for parvovirus, leptospira and erysipelas prior to breeding, and most need E. coli and clostridium vaccinations prior to farrowing. Many herds are weighing bi-annual SIV vaccination vs. pre-farrow flu vaccination. Again, weaned pig quality is the guide.

Autogenous vaccine products are being debated as organisms like SIV have changed. Commercial products will be the first choice for most for organisms like mycoplasma, SIV and erysipelas.

However, autogenously derived vaccines will likely be the choice for system-specific or herd-specific organisms like Haemophilus parasuis, Actinobacillus suis and possibly even E. coli and clostridium. Results should be measured and cost analysis instituted.

Growing Pig Population

Vaccination and herd health must be attended to regularly in both the sow herd and the growing pig population. Producers who have segregated themselves from the sow herd need to begin each new group with current information. The previous four group closeouts and the last four weeks of weaning are a good place to start.

Piglet receiving is the best chance to make plans for health and disease prevention. Systems with multiple sources have an even greater challenge to achieve this knowledge level.

Maternal Immunity Decline

Sow herd maternal immunity will decline at different rates for different disease organisms. It may also differ dramatically for organisms given as part of a pre-farrow vaccination program (i.e. SIV). Maternal immunity may be several weeks for SIV, but only days for Strep suis or Haemophilus parasuis.

Pulse dosing of feed or water-soluble antibiotics may be an effective method of preventing the over-growth of opportunistic bacterial organisms. Pulse dosing will help bridge the period from maternal protection to the piglets' immunity development.

Strategic placement of antibiotics also provides protection (from bacterial overgrowth) during periods of known exposure to viral organisms such as PRRS or SIV.

Monitoring of intervention strategies requires attention to details. Historical mortality and treatments are best broken down by week of entry (Figure 1). This allows production plans to anticipate problem areas. Seasonal variation is also necessary data.

Disease Intervention

A disease intervention strategy requires evaluation of multiple factors. The ileitis example (Table 4) illustrates how weekly mortality charts helped identify the problem graphically, and then cost-benefit analysis evaluated the solution economically.

Ileitis is an interesting disease model in that we have both a vaccine and feed-grade antibiotics for strategic placement. Economics and pig performance must both weigh in to monitor the results of this decision.

Oral vaccine technology has certainly made the grow-finish management of disease easier. Salmonella, ileitis and erysipelas can all be prevented today with appropriate use of these products.

Seasonal use of erysipelas vaccine in late winter will provide summer protection, although an injectable booster of erysipelas in the finisher is often necessary in severe cases. Ileitis and salmonella protection both appear to be quite strong when properly administered.

Value of Weaning Age

Often overlooked is exact piglet weaning age and its contribution to quality and growth. Recently published research from Kansas State University (KSU) evaluates long-term growth performance in relation to age at weaning.

The KSU research cites two age group sets for weaning: 12 to 21 days and 15.5 to 21.5 days. Death loss dropped from 9.4% to 3.6% as weaning age increased in the first age group and went from 3.9% to 2.5% in the second study. Piglet grow-finish throughput improved nearly 4 lb. for each day weaning age increased.

Furthermore, the grow-finish system achieved an increase in profitability of nearly 90¢ for each day added to weaning age.

Sow herds commonly resist increasing weaning age due to the illusion that weaning younger improves throughput. Weekly breeding variation further impacts the age variation among weaning groups.

In actuality, weaning later adds value to the sow unit two-fold: sow fertility is improved and subsequent total born number increases. There is also a dramatic reduction in wean-to-service interval in young-parity females. The cost to the sow unit may be the addition of farrowing crate space, about $2,000/crate for controlled environment, high-quality construction.

Don't Underestimate Management

Finally, management is still a major factor in disease prevention of the growing pig. Sow herd systems are producing PRRS-postive and mycoplasma-positive pigs into growing pig groups with nearly identical weaned pig quality and totally opposite grow-finish performance.

Receiving protocols must cover ventilation, feed budgets, antibiotics and vaccination plans. Numerous protocols have been established for “starting” weaned pigs. Producers must use proper management plans and then monitor pig quality. Daily stockmanship requires multiple feedings at delivery. Failure to do so can widen inequality among penmates.

Table 4. Ileitis Intervention Cost
Current Program Intervention Program
Population size, head 1,000 head 1,000 head
Mortality, % 12.83% 5.07%
Cost/dead pig, by age $70.00 $60.00
Mortality cost $8,981.00 $3,042.00
Med cost/pig (all) $2.50 $3.50
Total med cost $2,500.00 $3,500.00
Intervention savings (no credit for growth rate): $4,939.00*
*The savings reflect the difference in mortality costs and subtracting $1,000 for the higher medication costs during intervention.

Early feed management can prevent starvation and weakness in the first weeks after weaning. Feed budget allocation can also prevent cost over-runs in this growth segment.

Some producers maintain excellent air quality, feed quality, feed budgets and treatment protocols, while others fall terribly behind in some or all of these management areas.

Disciplined, planned prevention programs, followed by continual performance monitoring, allow producers to repeatedly achieve high quality, healthy production.

Table 3. Feedback Protocol

To control TGE, enteroviruses, parvovirus, rotavirus and E. coli, collect pig feces. For control of parvovirus, piglet tissues from mummies should be harvested.

Collection Procedures
Retain viscera from one stillborn and one newly born weak pig per 10 head of gilts.
Collect all the mummies that are available that day.
Collect ½ cup of manure per gilt to be fed back.
Mix this material with equal parts of cold water.
Feed two cups per gilt.
Feed at least twice per week for two weeks.
Begin the feedback when the gilts are in the isolation/gilt developer.
Include all females 2-3 weeks pre-farrowing to boost colostrum protection.