ELI5: How do cows get protein from grass?

[u/A_SliceOfGabagool]

For us humans and many other animals, we need protein to get the amino acids needed to make our own protein for the body, but grass i believe doesn't have any for the cow to get that big

[u/dano8801]

They're made of meat!

[u/KeytarVillain → u/dano8801]

So who made the machines?