I’ve heard of the ag lobby and the meat and dairy lobbies but never big grain. Of course they exist and do something but going against the meat lobby just seems weird.
-- 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 Slightly out of date source, but recent figures show this has only moved a few percentage points.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).
[1] https://www.usda.gov/sites/default/files/documents/coexisten... [2] https://www.usda.gov/sites/default/files/documents/coexisten...
They’re deeply tied to the meat industry so would benefit more from increased consumption.