My first job was on a dairy farm. Cows themselves aren’t smelly - no more than a horse or goat, not half as bad as a hound dog. They do belch a lot. Never saw one fart - that said, they had 30 or so cows, only one or two bulls at a time, who I never spent much time with. So maybe they fart, I can’t confirm one way or the other.
I found them smarter, kinder, and more gentle than anyone tends to give them credit for.
Wouldn’t have as a pet simply because their BMs are like if someone dumped a 5 gallon bucket of ......... And they do that about every half hour.
I would cow-sit though, as long as I don’t have to clean the barn.