Most of our dairy cows right now are one breed—they’re Holstein Friesians. They share a lot of genes, and this goes beyond how most animals in any breed share a lot of genes. 

We don’t just throw a bunch of cows and bulls together to mate, see. We identify the best bull (originally by observing everyone's offspring and awarding whichever bull sires efficient milkers), and then use him to impregnate as many cows as possible. Today, we’re looking at one legendary bull, Pawnee Farm Arlinda Chief. Pawnee sired 16,000 daughters, who in turn gave birth to many calves of their own. Three generations on, he had two million offspring.

Some of you already have your calculators out to determine just how many times Pawnee rutted per day, and are turning up some truly nonsensical numbers. That’s because we don’t let a champion like Pawnee just have sex with cows, since that’s nowhere efficient enough. Instead, we extract his semen (“that’s the fun part,” say some farmers, earning worried looks), dilute it, freeze it, distribute it, and impregnate more cows than he could ever service unassisted. 

So, a good 14 percent of all Holstein Friesians are Pawnee’s descendants. A fair number of them have a mother and a father descended from Pawnee. And here’s where we see the problems of artificially dispensing with genetic diversity. 

Pawnee had a mutation. It exhibited no negative effects in Pawnee himself. But when a cow’s fetus inherits a copy of this mutation from both parents, the gene expresses itself, which can result in a spontaneous abortion. It resulted in an estimated 500,000 spontaneous abortions, in fact, when you look at all of Pawnee’s offspring, and this added up to a total cost to the dairy industry $420 million. 

It must sound like everyone’s regretting putting their faith in Pawnee right about now. Except no: Even with that nasty mutation of his, Pawnee had so many other good mutations that he benefited the industry hugely. Cows with Pawnee genes make more milk, a boon for the dairy industry beyond normal milk production, one valued at $30 billion. Oh, and now that we’ve finally figured out what the deal is with that one bad mutation of his, we’re able to scan potential parents for it and keep it from doubling up and doing harm. Your defect will not be your legacy, Pawnee. Instead, we’ll remember you for producing white fluid in such high volumes. 

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For more cow news, check out:

Cows Have Best Friends

10 Famous Unsolved Mysteries Easily Explained by Science

Einstein Dreams About Electrocuting Cows, Creates Special Theory of Relativity

Follow Ryan Menezes on Twitter for more stuff no one should see. 

Top image: UC Davis

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