What I Have Learned About Cows

They get lonely, for starters. Graeme and Dora keep one bull for their 20-cow herd, and they make a steer to keep the bull company (can't keep a bull company with either a cow or another bull, so a steer is perfect). When they bring up the bull for mating, they bring the steer with him so that neither will get lonely. They are also scared of fire trucks (a rare sighting on a road so remote as Graeme and Dora's) - during lunch one day we watched the cows run frantically from one side of the field to the other and back again a few times before we heard the sirens and realized what was going on.
Mooing at cows is hit or miss - my friend and fellow wwoofer Katharina tried it on a hillside of calves, and they didn't take much notice. But she tried it again in Kerikeri with Marty's neighbor's cows, and before we knew it, all 35 cows had run over to the fence and had us in a staring match. The cows won of course.
And if you own cows, please make sure that their fences are all secure, because if the cows get through the fence, they will leave a sloppy pile of dung in the neighbor's pathway to the beach, and someone will have to clean it up.