This is sometimes true. However, e.g., about 4% of the farmland in California is used for alfafa, which is just for livestock. Alfafa is also a very water intensive crop.
Additionally, there are other uses that livestock corn feed could be put to if there weren’t so many damn cows, so it’s not like we’d be throwing away megatons of silage if it weren’t for cattle.
Commentary: We face a world potentially running out of antibiotics (www.channelnewsasia.com)