Let's not forget about cow farts. They are a major contributing factor, as well.
Which is amazing, because cows are physically incapable of farting. Horses, maybe. But the four-stomach set-up of a cow’s stomach is incompatible with the accumulation of gas. They get displaced, so that the poor cow can’t even defecate, and if they are not operated on to relieve the condition, they die. And when you feed them a high-carb diet to make them produce more milk, as is done with Holsteins, it becomes a big problem. Learned this while working with cows on dairy farms in the Florida panhandle.