You do have the practice in the far north (Saskatchewan, UK and some parts of the Dakotas) of using glyphosate as a desiccant on some grain crops to compensate for the short growing season, which probably affects the human food supply disproportionately (wheat is occasionally used for animal feed, but its use is trivial compared to corn and soy).

But given that the allowable limits for glyphosate in animal feeds is an order of magnitude or two higher than for people foods, I really would be surprised if livestock hasn't been eating a lot of it for the last twenty or thirty years.