Around 58 per cent of female pigs (called sows) give birth in farrowing crates in the UK.
This is a major concern because farrowing crates prevent sows from being able to turn around and sows are often not able to build their nests.
This is for up to five weeks, around the time of giving birth.
Not allowing sows to behave naturally can make them frustrated and stressed.
Another welfare problem is that many pigs in the UK only have slatted, bare floors to lie on and aren't given enough things to do.
Pigs are intelligent animals and not allowing them to express their natural behaviour can lead to boredom.