>>41777558Probably cows and to a lesser degree sheep and goats.
My headcanon is that thousands of years ago as ponies were developing agriculture they made a trade off similar to what happened with herder and pastoral peoples in our world. The ponies would protect the milk producing animals and defend their grazing land, and in exchange those animals would produce milk for them and surrender some control over their reproduction to the ponies who would manage them as livestock. Selectively breeding them for more desirable traits.