Binro the Heretic
Because that is a bull. In the opening shot, you can clearly see his bullhood under his belly which they later pixelate when he mounts the farmer.

I'm not exactly sure how modern ranches work, but the old-fashioned way of collecting "bull's milk" was to keep them isolated to the point that the sight of another, younger bull would arouse them to the point they'd be willing to mount anything. Then, the ranch hands would roll a little metal-roofed wagon draped in cowhide into the pen. Inside the wagon was a ranch hand with a double-layered rubber tube filled with warm water. The bull would mount the wagon and the guy in the wagon would slide the tube over the bull's member. The bull would blow his load into the inner pocket of the tube and dismount. The wagon would then be pulled out of the pen.

I think nowadays they just snake thin tubes up the old boy's plumbing to collect a deposit, but again, I'm not exactly sure.

Anyway, it looks like this bull accidentally came in contact with a smaller bull and got turned on. Then, when the ranch hand entered the pen, the bull tried to relieve his tension.

Smellvin
I thought they were blurring out the udders (because of cow in the title probably). The bull penis makes more sense.

fluffy
Of course the goofy announcer keeps referring to the cow as female.

baleen

Binro, don't you fuck animals?

Binro the Heretic
Of all my many problems and flaws, that is not one of them.

I think Alfred Shitcock was into that, though. Or I might be thinking of some other PoE denizen.

Gwago
That's what the cow said. Hey-ho!