Cow blowing (insufflation) to encourage milk letdown

So, I’m reading this book on milk (Milk: A global history by Hannah Velten) when I come across this picture on the right and I’m thinking “OK, this is looking a bit strange, and is surely quite disconcerting for both species.”

The photo was taken in 1982. It is a young lad blowing, via a tube, air into the vagina of a cow to induce milk letdown. I have read that similar result can be achieved by blowing air into the anus.

I know what you are thinking:

1. No, no, no, you are kidding me, right? No. It’s true, and it’s called “cow blowing” or insufflation. It has been described in many parts of the world, and the “art” has been around for a long time. Back in 440 BC a bloke called Herodotus described this in horses: “... they insert a tube made of bone and shaped like a flute into the mare’s anus, and blow; and while one blows the other one milks.”

2. OK, who was the first person to think of this?

“Hey Dad, Daisy won’t let down any milk, what should we do?”

“Have you tried scratching behind her ear?”

“Yes. Didn’t work.”

“What about rubbing her tummy”.

“Doesn’t work either".

Dad, stuck for ideas, decides to play a joke on the kids. “Try blowing air up her backside.” And so the incredible discovery began.

Seriously, I would like to know the physiology behind this practice, but I had difficulty getting an answer. Is it a physical response or does the air stimulate the release of oxytocin? Anyway, there is a fascinating, although long, history of insufflation of cattle here. There is also a short TV news video here. When food is not always easy to come by you have to admire human ingenuity to get nutrition.