No, really. There is a logic.
If you have a cow on your property, your land is classified as agricultural rather than residential... and property tax on agricultural is close to zero. Cows are low-upkeep and eat grass. So. You actually save money by owning cows. Big and apparently frequently-exploited loophole.
So if you're driving to my parents' house (known as Stately Ravensnatch Manor by felisdemens & co.) and going WTFCOW every few blocks? Now you know.