The milk has an effect on him: he’s becoming more bull-ish.

Once Tom had a taste of the cream, he couldn’t stop. Moving from one nipple to another, he started doing his best to drain Sarah dry. Not that she minded, his bovine wife was lost in a haze of ecstasy, shivering in pleasure as he drank from her udder. It was only as Tom started getting full that he remembered something about his wish.

He’d based Sarah’s changes off his fantasies, but the milk of a cowgirl was a common element in those very fetish stories. More often than not, the milk of an anthro cow had its own transformative properties. Just as he began to worry about that, pulling away from the udder, Tom felt his body warm up as changes started to touch him.

Now, he hadn’t actually drank that much milk, so the changes weren’t too major. His body hair became more like fur, thicker and darker all over his body. His body, once a bit out of shape, suddenly became a bit stronger, with thicker muscles, though he didn’t lose any of his belly fat, it just rested over the harder muscle. Lastly, his cock, normally at most average sized, grew longer and thicker, as well as changing its shape, until it looked like a bull’s cock. To match this, his balls expanded too, until they were each larger than a tennis ball.

Tom hadn’t been the only one watching the changes wracking his body. In fact, Sarah was looking at him with more lust and desire than he’d seen from her in a very long time. “Looks like my milk is contaminated,” she said, without even the hint that it was a bad thing. “And I’ve got my own bull now.” This time, it was her turn to feel up his changed body, and Tom was left in the awkward position of feeling embarrassed by his still rather pudgy dad bod while also being turned on, both by his changes and the attention. Their sex that night was truly animalistic, and Tom wasn’t about to complain about it