In the U.S.A., housing for the lactating sow and her piglets can be divided into five main areas. Total confinement, defined as the farrowing crate, houses the highest number of at 83.4 plus or minus 4.0%. Remaining operations house fewer sows with open buildings that have outside access at 12.4 plus or minus 4.1%, open building with no outside access, 2.9 plus or minus 0.5%, lot with hut or no building, 0.6 plus or minus 0.2% and pasture with hut or no building the lowest at 0.7 plus or minus 0.3% (. In the U.K., it is estimated that around 70% of sows farrow in crates, 27% farrow outdoors in farrowing arks and only 3% farrow in loose-housed indoor systems.
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