By Al Leman.
Historically, pigs were reared in a pasture setting with individual farrowing hutches for each sow. For the past 30 years in the United States, the trend has been toward confinement.
First, sows were moved into a central farrowing house. The early confinement systems utilized a pen for the sow and her litter. Around the outside of the pen, guardrails reduced the number of crushed pigs.
These soon gave way to farrowing crates, which are commonly 2 feet wide by 7 feet long. The sow is restrained in the crate so she is less likely to crush her baby pigs. At first, sows were taken from the crate twice a day for feeding and watering.
Today, however, sows spend their entire lactation period in a farrowing crate, often with automatic feeding and watering. The trend toward confinement has continued, until now an estimated 75 percent of the pigs are reared in some kind of confinement. The term "total confinement" refers to the entire life cycle of the pig being inside buildings. Sow housing may feature pens of sows or sows in individual stalls or tethers.
Nursery housing for pigs begins after they are weaned, commonly from 4 to 10 weeks of age or when pigs weigh 15 to 50 lbs. The growing phase of production is commonly from about 50 lbs. until about 100 lbs., and the finishing stage is commonly from 100 to 220 lbs. or market weight.
In the past 20 years it has become common practice to rear pigs on slotted floors to allow urine and manure to pass through the floor to a pit or gutter system below. The attempt, of course, is separation of the pig from its fecal material.
Two types of common finishing facilities are called totally slotted or partially slotted, depending on the flooring in the building. The partially slotted floor usually consists of a 2/3 solid floor with a 1/3 slotted floor.
Abrasion-free floor surfaces help promote normal hoof development and wear, lessening the chance of damage, infection and lameness. Floors made of expanded metal and wire mesh offer an excellent opportunity for baby pigs to be born in a manure-free environment.
Besides floor surfaces, other factors influence transmission of pathogens. Solid partitions between pens help reduce nose-to-nose contact and disease transmission. Solid walls help separate groups of pigs and encourage all in, all-out production.
All in, all-out production is an effective, yet underused, method of disease control. It encourages age separation of pigs and facilitates cleanup between groups. All new building and housing systems should be designed with this concept in mind. Existing facilities often can be improved by partitioning pigs into smaller groups.
With the trend to confinement, providing fresh air to swine becomes a vital part of reducing disease. Fresh air helps dilute the concentration of microbes, harmful gases and dust. It promotes healthier respiratory tissue, which in turn reduces the dose of microbes that get deep into the lung tissue.
The amount of fresh air is a function of the ventilation system, animal density, volume of space per animal, and the waste management system. There is evidence that pigs with about 4 cubic yards or more of air volume have fewer lung lesions at slaughter than pigs with less air volume.
Current winter ventilation systems in fully slotted barns over a full anaerobic pit do not support optimum performance. Future pork production will feature aerobic waste systems, or more air movement than currently is being provided.
Al Leman is Swine Extension Veterinarian, College of Veterinary Medicine, University of Minnesota, St. Paul.