Don't do drugs. Harass people who wear fur coats. Remind them that an innocent baby seal was mercilessly clubbed. They hate that. And don't ever eat meat.
Cows are animals, just like humans are animals.
That means that they have rights. No, not always. Sometimes killing can be justified, like in the Persian Gulf. You have to be able to tell when an animal has rights, and when it doesn't. If an animal is rare, pretty, big, cute, furry, huggable, or lovable, then it has rights.