Swine: health management


John Carr .



Keywords: Swine, health, biosecurity, pigflow, environmental medicine.



The clinical appearance of many ‘diseases and disorders’ of farmed pigs is heavily influenced by the pigs’ environment.  The classical concept that ‘pathogen meets pig results in clinical disease’ is nearly always incorrect.  The pig industry and its servicing veterinary advisors have moved from individual animal medicine through preventative medicine into health maintenance.  All of the skills learned previously still need to be employed, but veterinarians are now required to apply a degree of animal science knowledge, for which they are rarely prepared.


To maintain the health of swine the clinician needs to approach the pig unit with regard to six major areas:

Biosecurity, pig flow, medicine management, review of current stock health and susceptibilities, competency of the stockpeople and the provision of an environment conducive to healthy pigs


Managing the health of pigs on a farm must become the responsibility of a farm health team, which includes a veterinarian. However, the key players are the stockpeople, and if their training is inadequate, disease recognition will be delayed with potentially devastating consequences both for the pigs involved, the farm and even nationally. This was classically demonstrated by the 2001 Foot and Mouth Disease outbreak in the UK where failure of the producer to recognize and report clinical signs of FMD in his pigs to his local veterinarian resulted in the unnecessary deaths of 6 million animals to control the disease1.



Biosecurity is a major responsibility of the farm health team.  Awareness of the ease of disease spread is required for all members of the farm health team.  It is impossible (at present) to prevent the transmission of some diseases; for example various serotypes of Escherichia coli or earthborne pathogens such as Erysipelothrix rhusiopathiae.   Some diseases may spread long diseases through the air, for example Parvovirus. Other pathogens are only locally spread, for example, Mycoplasma hyopneumoniae will affect farms within a 3 km zone.  However, if your farm is located in an area of low farm density, maintenance of a M. hyopneumoniae free status has been possible for more than 20 years2.  Some diseases, such as Sarcopties scabiei var suis, require direct pig contact.  With modern avermectin therapies eradication of mange on pig farms is achievable.   Adequate biosecurity is the responsibility of the entire pork production chain, from the nucleus and multiplication farms with their AI studs to the family farm. A pathogen which is absent from the farm or area, such as Pseudorabies (Aujeszky’s Diseases), does not require treatment or prevention.  Indeed, the absence of pathogens allows for more errors in environmental management before production suffers.


Pig Flow

The lack of animal science understanding by the veterinary profession has allowed farms to grow without regard for the biology of farmed pigs.  Producers are driven by the need for an economic return and constraints of buildings and local legislation.  Veterinarians and producers have turned to antimicrobials to balance pathogen load against health and disease.   Over time, with inadequate cleaning, environments become infected with an increasing number and variety of pathogens.  Eventually the disease challenge overwhelms the natural defense mechanisms and increasing number of pigs present with clinical disease.  The easiest way to control the pathogen load is to move clean pigs into new buildings.  This is clearly impossible in a farm environment.  However, an approximation can be reached by adopting strict all-in/all-out combined with single source policies.  All-in/all-out is poorly understood by the farming community.   The keystone must be pig flow.  The provision of pigs of the same age and health status is only achieved by minimizing the variation in pig numbers produced per batch by no more than 15% overall - 5% below target output and equally important, no more than 10% above target output.   This creates stable farms and helps to reduce greed in producers.  In several parts of the world legislation regarding stocking density (EU3) is forcing farmers to adopt pig flow measures because failure will result in fines and other penalties.

Pig flow is a complex concept which prescribes the number of animals which the farm can accommodate and then models a production method to fill these buildings4.  The area where pig flow fails on most farms is the gilt pool.  Having insufficient gilts results in a reduction in output.  Poor management of the gilt pool results in a glut of gilts in oestrus, resulting in overproduction and overstocking of the facilities.

Figure 1.

Pig Flow model for a 20 sows a week farm


Gilts                                        Bred                              Farrow                                            Finished kg – 80 kg

Text Box: 2
Text Box: 24
Text Box: 20
Text Box: 15200


                   10 weeks                             17 weeks                                  26 weeks


With specific records of:

Gilt pool 95 kg to service                                    12-15

Females a batch to serve                                   24 

Sows a batch to farrow                                      20

kg to wean per batch                                          1600

kg a batch to sell                                                  15200

kg paid for annually                                           182400

pigs sold annually                                                9880


There are some targets that have to be met:  The farm weans weekly; the ninety percentile farrowing rate is 82% (the farrowing rate is over 82% ninety percent of the time); 10 piglets weaned per crate with an average weight of 8 kg at 24 days of age; a 5% post-weaning mortality, therefore 95 pigs at 80 kg dead weight are paid for each week.  The gilts are given 10 weeks introduction to allow for adequate compliance with biosecurity arrangements.  In addition to take finishing pigs to 80 kg dead weight requires 26 weeks.


Medicine management

Medicine storage and usage is the cornerstone of any preventative medicine programme.  The diagnosis of increased coughing and mortality in finishing pigs associated with Swine Influenza Virus or M. hyopneumoniae may result from the freezing of the vaccines in the farm, veterinarian or distributor’s refrigerator. A study of farm medicine storage areas revealed 10% of farms stored their vaccines below 0oC5.

The inappropriate use and overuse of needles and syringes have been demonstrated in the transmission of many pig pathogens, including Porcine Reproductive and Respiratory Syndrome Virus and Classical Swine Fever virus.

Figure 2.

Vaccines stored in a ‘freezing’ refrigerator on a farm experiencing finishing pneumonia despite ‘vaccination’.


Stock health

The ability to clinically examine, recognise and treat disease in pigs is the responsibility of the entire farm health team.  Adequate training in the recognition of disease by stockpeople is a responsibility of the farm’s attending veterinarian.  Continual professional development is a prerequisite of the veterinarian as new diseases appear (Post Weaning Multisystemic Syndrome) and established diseases (Glasser’s Disease) evolve in the modern pig industry.  The pig itself carries the ability to succumb or fight disease agents.  As the pig’s genetic make-up becomes more understood, commercially available resistance factors will include more than just Escherichia coli F4 or F18 resistance6.  A major problem in pig health management is compromised or sick pigs, who are major sources of disease pathogens.  It is essential that farms provide hospital accommodation and suitable treatment regimes to provide for these pigs.


Stockperson and stockmanship

The fulcrum around which pig health revolves is the stockperson’s abilities.  Modern pig farming has a greater reliance on employed help, who may have little interest in the well-being of the pig. The NPB SWAP7 initiative concentrates on the pig’s behaviour towards the stockpeople. A caring environment promotes good health and productivity8.


Environmental management

The expression of clinical production diseases is often determined by the environmental stressors to which the pigs are subjected.  Assessment of the environment can be easily achieved when the environment is broken down into its component parts – the water supply, the feeding system, the flooring and the air.

Water supply

A supply of fresh drinking water is essential to pig health.  A drinker which provides water is generally accepted as good enough by untrained stockpeople.  However, the flow may be inadequate, the drinker’s height inappropriate, the drinker type unsuitable, the water contaminated or stray voltage affecting the drinker.  If these factors are not recognized and corrected by the stockpeople, then performance and pig health will be negatively affected.

Feeding system

Growth rates are determined by the ability of pigs to eat.  The type of feed, presentation of feed and hygiene of feed are factors which the farm health team needs to constantly assess to ensure that health and production are maintained.  In addition to swine health, feed wastage plays a key role in profitability of swine farms, yet farms may casually waste 10% of the feed.  Poorly constructed feeding systems impact the quantity and type of dust that is aerosolized during feed distribution.  This can impact both stock and stockpeople health.


Stocking densities for all stages of pigs are becoming a legal constraint on pig production throughout the world.  Pig health improves with increased space allowance per pig but pork output is seriously negatively impacted.  Therefore, an acceptable balance between space and production is required.  As farms age, flooring and other contact surfaces (walls, doorways and passages) become eroded, particularly around feeders and water supplies.  Poor maintenance routines ultimately result in compromised pig health.  Analysis of the floor would also include hygiene.  The lack of all-in/all-out routines result in poor or inadequate cleaning routines and maintenance.  It is only through good pig flow that sufficient time be set aside to allow stockpeople to adequately care for the floor.


Failure of the ventilation system is the classic reason for respiratory disease.   Seasonal variations put tremendous pressure on the ventilation system which fails particularly at the turn of the seasons.  Managing the ventilation system requires assessment of the air variations over time with reference to the temperature, humidity, gas pollutants (NH3, CO2, CO, H2S); dust and type and endotoxins.  All buildings should be designed to provide adequate living zones for the pigs – sleeping, eating and drinking, exercise and dunging.   The building engineers should ensure the building works before and during pig occupancy.  When failures are discovered, they should have rational improvements that can resolve the situation.  Poor building orientation, particularly in cross-flow ventilation buildings, result in drafts, creating poor pig respiratory health and increased vices, necessitating tail docking to control the situation. Pre-weaning diarrhoea is often associated with drafts and chilling of the neonatal piglet.


Figure 3

Environmental management directly impacts the health of pigs.  The photograph shows water which is difficult to obtain, a feeder which is too short, broken flooring and dirty fans which reduce air flow in a building.  All of these and other problems directly compromised pig health.




Swine health management maintenance requires a balance between reducing the risk of new pathogens through biosecurity; providing all-in/all-out though pig flow; requiring that medications are effective through proper use and storage; recognizing sick animals promptly; providing excellent stockmanship and ensuring pigs are not compromised by any failing in their environment.   




1 Foot and mouth

2 Muirhead, M.R. and Alexandra, T.J.L. (1997).  Managing Pig Health and the Treatment of Disease.  Published by 5M.  ISBN 0 9530150 0 9

3 EU legal

4 Carr, J. (1999). Development of Pig Flow Models.  Pig Veterinary Journal 43: 38-53.

5 Carr, J. (1999).  Refrigeration Management.  Pig Veterinary Journal 43: 138-143

6 F18 resistance

7 NPB SWAP program

8 Hemsworth work.