This is rectal palpitation. It is a method of diagnosis where one inserts one's hand into an animal's anus and spreads the fingers in the rectum in order to check for pregnancy or internal diseases. This technique is also called "palpitation" for short.

Akigumo said there'll be more opportunities for gags this way, compared to drawing a normal cow. And it'll be fun, more than anything! ...So she said.

Now, now, it's just a drawing, isn't it? Nothing to get angry over, really.♪

I wouldn't mind if it were me.