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 by the 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 numbers 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, but an approximation can be reached by adopting strict all-in/ all-out procedures 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 the pigs of the same age and health status is achieved only 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 procedures. In several parts of the world, legislation regarding stocking density, as in the European

Union,[3] is forcing farmers to adopt pig flow measures, because failure will result in fines and other penalties. Pig flow is a complex concept that prescribes the number of animals the farm can accommodate and then models a production method to fill these buildings.1-4-1 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 estrus, resulting in overproduction and overstocking of the facilities (Fig. 1).


Medicine storage and usage are the cornerstone of any preventive medicine program. The diagnosis of increased coughing and mortality in finishing pigs, associated with swine influenza virus or M. hyopneumoniane, may result from the freezing of vaccines in the farm, veterinarian, or distributor's refrigerator. A study of farm medicine storage areas revealed that 10% of farms stored their vaccines below 0oC.[5]

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 (Fig. 2).


The ability to clinically examine, recognize, and treat disease in pigs is the responsibility of the entire farm

Gilts Bred Farrow Finished kg - 80 kg





10 weeks 17 weeks 26 weeks

With specific records of:

Gilt pool 95 kg to service


Females a batch to serve


Sows a batch to farrow


Kg to wean per batch


Kg a batch to sell


Kg paid for annually


Pigs sold annually


There are some targets that have to be met: The farm weans weekly; the 90 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% postweaning mortality, therefore 95 pigs at 80-kg deadweight 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 deadweight requires 26 weeks.

Fig. 1 Pig flow model for a 20 sows per week farm.

Fig. 2 Vaccines stored in a freezing refrigerator on a farm where pigs experience finishing pneumonia, despite vaccination.

health team. Adequate training of stockpeople in the recognition of disease is a responsibility of the farm's attending veterinarian. Continual professional development is a prerequisite for the veterinarian as new diseases (postweaning multisystematic syndrome) appear and established diseases (Glasser's disease) evolve in the modern pig industry. The pig itself carries the ability to succumb to or fight disease agents. As the pig's genetic makeup becomes more understood, commercially available resistance factors will include more than just Escherichia coli F4 or F18 resistance.1-6-1 A major problem in pig health management is compromised or sick pigs, who are the major sources of disease pathogens. It is essential that farms provide hospital accommodations and suitable treatment regimes to provide for these pigs.


The fulcrum around which pig health resolves 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 National Pork Board's Swine Welfare Assurance Program initiative1-7-1 concentrates on the pig's behavior toward the stock-people. A caring environment promotes good health and productivity.1-8-1

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