Do pigs sweat? It seems that pigs or rather swine (because 'pig' is actually a young animal) do have sweat glands but they are so few that they are not efficient temperature controllers and so they cool down by wallowing in cool water or mud, which has the same effect as sweat evaporating on human skin.
Perhaps we should adjust our idioms.
When I was young(er) I was told 'Ladies glow, gentlemen perspire and horses sweat' at the same time as I learnt that Officers marry Ladies, NCOs have wives and other ranks consort with women.
Class-ridden Great Britain?? Never!