To contextualize this given the parent commenter's question:
-- About 50% of US corn production goes toward animal feed (and another 30% goes to ethanol). Slightly out of date source, but recent figures show this has only moved a few percentage points. [1]
-- Over 70% of US soybean production goes toward animal feed. [2]
-- I wasn't able to find something similar about wheat, but I would guess nearly all of it is human consumption.
Given this, it's safe to say that a large portion of these grain subsidies are linked to meat, although to get a better idea of the distribution, we would need to see a further breakdown by category (corn, soybeans, wheat).
I think mahogany’s comment is more important but I just want to add: how many subsidies they get doesn’t relate at all to what research they might fund.
They’re deeply tied to the meat industry so would benefit more from increased consumption.
https://www.thoughtco.com/us-farm-subsidies-3325162