Gestation crates

A gestation crate, also known as a sow stall, is a metal enclosure used in intensive pig farming, in which a female breeding pig (sow) may be kept during pregnancy and for most of her adult life. A standard crate measures 6.6 ft x 2.0 ft (2 m x 60 cm).

Sow stalls contain no bedding material and are instead floored with slatted plastic or metal to allow waste to be efficiently collected below. This waste is then flushed into open-air pits known as lagoons. A few days before giving birth, sows are moved to farrowing crates where they are able to lie down, with an attached crate from which their piglets can nurse.

There were 5.36 million breeding sows in the United States as of 2016, out of a total of 50.1 million pigs. Most pregnant sows in the US are kept in gestation crates. The crates are banned in the European Union, Canada, and in nine states in the US (Arizona, California, Colorado, Florida, Maine, Michigan, Ohio, Oregon and Rhode Island). However, farrowing crates, in which female breeding pigs can be kept for up to five weeks, are not banned.

Opponents of the crates argue that they constitute animal abuse, while proponents say they are needed to prevent sows from fighting among themselves.

Between 60 and 70 percent of sows are kept in crates during pregnancy in the United States. Each pregnancy lasts for three months, three weeks, and three days. Sows will have an average of 2.5 litters every year for three or four years, most of which is spent in the crates. They give birth to between five and eight litters before being culled from the herd. Some older sows may reach a size at which they have to sleep on their chests, unable to lie on their sides as pigs usually do. The floors are slatted to allow excrement and other waste to fall into a pit below.

A few days before giving birth, sows are moved to farrowing crates, which are slightly wider so they can lie down to nurse. Crates have 18-in. (46-cm) "troughs" on each side where the piglets can safely lie without being in danger of sow overlay (when the sow lies down on top of a piglet).

Piglet survival also depends on selection pressure. Groups of piglets bred for higher survival showed no difference in mortality when weaned in farrowing crates and outdoor systems.

Although farrowing crates have been used based on the assumption that they reduce piglet mortality rates, there appears to be little published evidence in support of this claim. Perhaps the most comprehensive publication to date on this subject concluded that there is no significant effect of housing on overall piglet mortality, the authors stating that “Despite the fact that the crate system has been considered to reduce piglet mortality mainly through a reduction of crushing, there is not much scientific evidence for this when considering the few large surveys that compare the mortality rate in commercial herds“. The review goes on to describe several large studies dating from as early as 1983, the majority of which found no difference in piglet mortality rates between loose and crated sows. The review also details a convincing argument as to why piglet mortality rates have been reported to be somewhat higher in a comparably small number of studies, citing methodological flaws.

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