Do cows sleep standing and lying down?

Horses sleep standing up because they are a prey animal thus they need to be able to get away from any dangerous situation quickly. A horse that is laying down cannot get up and run from danger nearly as quickly as a horse that is standing. Horses also sleep standing up for the most part because they are so heavy that laying down for an extended period of time puts significant pressure on the tissues on the downward side of the horse and can lead to tissue damage and tissue death. Horses do need to lay down to sleep for about 45 minutes a day in order to achieve REM sleep and remain well-rested, but they tend to do this at times and in places where they feel very secure. Horses who are in unfamiliar or frightening surroundings or cannot lay down due to a health issue can actually become sleep deprived if they are not comfortable enough to lay down.