Horse 'cubes'

[Alnico]

An unimportant question I know, but my (horse-owning) partner couldn't answer this one. Why are horse cubes called 'cubes'? There's nothing remotely cubical about them. Why aren't they horse pellets?

Were they actually cubes in the past, and the name has just stuck? Or is the origin more to do with three axes of nutrition (along the edges of a cube)?

 

[Tnavas]

It's a really strange name for them - I've always remembered them as being cylindrical.

 

[xloopylozzax]

Sheep feed the same shape is called "nuts". It is an odd name I guess...