Horses were a primary means of transporation. Traditionally, about 1/3 of agricultural production was applied to feeding horses.
Even if accurate, you are talking about a time when people largely grew, raised, and hunted their own food. Horse feed was also supplemented by grazing, or rather grazing was supplemented with sweet-feed.
Technically, though, I suppose your statement is accurate. I just think comparing the two is the whole apples and oranges thing. People and horses both ate oats and corn. Still do. It’s adding internal combustion engines to the mix that screws everything up.