Proper management can increase reproductive performance and feed utilization and decrease mortality. Disease in farm animals is often the result of inadequate management, allowing for proliferation of commensal microflora or the introduction of a pathogen (eg, porcine reproductive and respiratory syndrome virus, PRRSV) to the population. Properly managing the interaction between pigs, people, and the environment, along with effective biosecurity, has a positive effect on controlling the level of commensal organisms within the population, the introduction of new pathogens, disease expression, and productivity of the herd. In many cases, clinical disease is merely the indicator of failure in one or more of these interactions. Treatment of disease through chemotherapy is a first step in disease control, but elimination of the underlying environmental or management problem is the most important one.

When large numbers of pigs are housed together, pig-to-pig and pig-to-environment interactions are enhanced, and manager-to-pig interaction is diminished. These are the bases of disease problems on intensive swine farms, and an understanding of their consequences is necessary to reduce health-related losses in modern pig enterprises.

On poorly managed farms, ~30% of pigs born alive do not survive to market weight. For example, ~15% die before weaning, 10% in the nursery, and 5% during the grower-finisher stages of production.

Survival of neonatal piglets during the first 7 days depends on 3 major factors: 1) adequate intake of energy, 2) suitable environmental temperature, and 3) passive transfer of immunity from the sow. Because piglets are born with limited glycogen reserves, they need to replace and add to their energy reserves within hours of birth. If energy (colostrum) is not acquired, mortality due to hypoglycemia follows. Hypoglycemia (see Management of the Neonate: Immediate Postpartum Care) probably is the most common cause of piglet death. Several management procedures may reduce these starvation losses. For example, equalizing piglet weights within litters by cross-fostering in the first few hours of life eliminates or markedly reduces losses and can have a dramatic effect on overall mortality rates. Another important management factor is proper thermoregulation of the lactation area. During lactation, piglets are sensitive to low environmental temperatures, and should be born and maintained for 1 wk in environmental temperatures of 86–93°F (30–34°C).

In addition to its vital role in supplying energy, colostrum supplies piglets with antibodies to protect them against common infections. The most common fatal infection is intestinal colibacillosis (see Intestinal Diseases in Pigs: Enteric Colibacillosis in Pigs); losses can be reduced by vaccinating the sow, which provides antibodies to the piglets via the colostrum and, especially against gut diseases, via the milk.

Any sow disease that results in decreased milk production increases susceptibility to diarrhea, as does low environmental temperature, which slows gut motility. (Also see Postpartum Dysgalactia Syndrome and Mastitis in Sows.) Slower passing of milk and its antibodies through the intestines enables E coli to adhere more readily to the intestinal wall and then produce enterotoxins that cause excess secretion of the intestinal cells and diarrhea.

Significant numbers of piglets die from crushing in the first few days after birth. The sow is likely to lie on piglets if she is clumsy, if the warmest spot in the farrowing pen is next to her, or if the piglets are hypoglycemic and sleepy. Suitably designed farrowing crates and correctly placed heat lamps can minimize losses from crushing, although they are unlikely to completely eliminate them.

Careful attention to these management factors usually reduces neonatal mortality to 5–10%. Even in extensive systems, at least some of the neonatal pig mortality is due to management and, to this extent, avoidable.

In today's swine industry, no agent has affected performance of nursery pigs more than PRRSV (see Porcine Reproductive and Respiratory Syndrome). Following introduction of the virus to the nursery through the entry of infected pigs at weaning, PRRSV circulates from room to room; older infected pigs become the source of virus for newly weaned piglets after loss of maternal immunity at 4–6 wk of age. Endemic PRRSV in nursery and finisher pigs has significantly reduced growth rate and increased mortality, feed conversion ratio, and vaccination and medication costs. However, management strategies such as partial depopulation, all-in/all-out pig flow, and vaccination have been very effective at reducing the severity of the disease.

In farms that are free of PRRSV, fewer pigs die (2–3% nursery mortality is considered acceptable on a commercial basis). In the absence of PRRSV, the major infectious disease is diarrhea, but starvation and inadequate growth are also problems. Weaning is a particularly stressful period due to changes in diet and surroundings and often in social order. Generally, the earlier the weaning, the more important management becomes. At weaning, piglets should have enough trough space to allow them all to eat at the same time. The inclusion of feeding boards for the first 5–7 days after weaning enhances feeder space and promotes group feeding. Piglets should have ready and continuous access to acidified water but should be fed small amounts of feed frequently (3–5 times a day) for the first week after weaning. The quality of the feed enhances intake, and diets that are fortified with plasma protein and milk products are required. Environmental temperature is also critical—pigs maintained in suboptimal temperatures frequently succumb to diarrheal disease. Depending on the age of pigs to be weaned, environmental temperatures should be maintained at 77–80°F (25–27°C). Size at weaning is as important as age; small pigs are more likely to starve or have diarrhea. Oral fluid therapy is a good adjunct to antibiotics in the prevention and treatment of postweaning diarrhea.

Finally, due to the warm nursery environment, skin diseases such as exudative dermatitis (greasy pig disease) may be more prevalent, secondary to high humidity. Streptococcus suis and Haemophilus parasuis infections also develop in intensively maintained, recently weaned pigs.

Regarding the growing-finishing area, allowing for sufficient pen space is important to reduce crowding, stress, and pathogen transmission. Space recommendations for growing pigs are based on a report by the Nutrition Council of the American Feed Industry Association (see Health-Management Interaction: Pigs: Space Needs of Growing-Finishing Pigs). When maintained on slatted floors, each growing-finishing pig should be provided 4–6 sq ft of floor space from 50–125 lb, and 8 sq ft from 125–240 lb body wt. Pigs carried to heavier weights (eg, 270 lb) may be more efficient if allowed 10 sq ft, but that recommendation is difficult to justify economically.

Table 1
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Space Needs of Growing-Finishing Pigs Weaning to 75 lb (<34 kg) 75–125 lb (34–57 kg) 125 lb to Market Size (>57 kg) Sleeping space or shelter per pig (square feet) 4 5–6 8 Pigs per linear foot of self-feeder space (or per hole) On dry lot 4 3 3 On pasture 4–5 3–4 3–4 Percent of feeder space for protein supplement On dry lot 25 20 15 On pasture 20–25 15–20 10–15 For hand-feeding or hand-watering, running feet of trough per pig (access from one side) ¾ 1 ¼

The greatest economic losses due to inadequate management are seen in the grower-finisher stage of production. Respiratory diseases (such as Actinobacillus pleuropneumonia, enzootic pneumonia, and PRRS) and intestinal diseases (such as ileitis) significantly reduce growth rate and efficiency of feed utilization.

The most significant management technologies recently adapted in the nursery and grow-finish areas are all-in/all-out animal flow and segregated early weaning. All-in/all-out production systems greatly enhance grower-finisher productivity and disease control and can be adapted to room, building, or site. Segregated early weaning consists of segregation of the weaned pig from the sow at an early age (14–16 days). Most infections early in life are derived from sows during lactation. If each week's production of weaners is isolated from the sow, the chance of infection spreading to each batch of new pigs is reduced. Nursing pigs are protected, to some extent, from infections carried by their dams through colostral antibodies. Weaning at an early age, before the colostral antibodies have been lost, reduces the chance of the piglets being infected from their dams. Advanced systems combine segregated early weaning with all-in/all-out animal flow to prevent the transmission of pathogens from older, previously infected pigs to younger, more susceptible pigs. Finally, combining segregated early weaning with all-in/all-out animal flow and housing the sow herd, nurseries, and growing-finishing population on separate sites forms the basis for multi-site production.

Together, these technologies represent a major development in production and disease control. They are not, however, completely foolproof. In some cases, they may merely delay the development of clinical disease to a later age group, particularly S suis and H parasuis infections. But in most herds, practicing this form of continuous depopulation and repopulation has notably improved productivity and disease control.

Finally, proper biosecurity is essential to protect the health and productivity of the farm. Selecting a breeding stock source that is free of PRRS virus, Actinobacillus pleuropneumonia, Brachyspira hyodysenteriae, transmissible gastroenteritis virus, and sarcoptic mange is critical. After purchase, animals should be quarantined and tested before entry. Protocols should be in place to limit visitors, control rodents, and ensure the safe introduction of personnel (shower in/shower out) and shipments (fumigation rooms). A site and protocol for cleaning and disinfecting transport vehicles is necessary, particularly in multi-site systems that rely on frequent movement of pigs across the country. Finally, the application of air filtration systems to prevent the introduction of airborne pathogens may be important for artificial insemination centers and breeding stock multiplication units. (Also see Biosecurity.)

Last full review/revision July 2011 by Scott A. Dee, DVM, MS, PhD, DACVM