Dear Suzy,
I love a saucer of milk. But that’s usually cow milk or maybe goat milk.
I asked my friend Kim Davenport why nobody drinks dog milk. She studies dairy cows at Washington State University.
She told me dogs don’t make extra milk.
“We’ve selected cows to make more milk,” Davenport said. “Whereas dogs make enough milk for their puppies, and that’s about it.”
The amount of milk a dog makes varies a lot. It depends on the dog’s size, breed, age, how many puppies they have and how old those puppies are. Even a large dog nursing a big litter might produce about three quarts of milk a day.
Dogs usually only nurse their puppies for a few weeks. Their milk has more protein and fat than cow milk, which may help the puppies grow quickly.
Today’s dairy cows produce gobs of milk. They usually make 6 to 9 gallons of milk every day—and sometimes much more. And they can nurse their calves for months.
This is an approximation of how much milk a large dog and an average dairy cow make per day. Since 4 quarts equal 1 gallon, this dairy cow would make about 36 quarts of milk.
It wasn’t that way for the extinct ancestors of today’s dairy cows. They were called aurochs.
Aurochs likely made just enough milk to feed their calves. We don’t know exactly how much that was. But wild cows today produce about 2 gallons of milk a day—much less than modern dairy cows.
Scientists think that ancient humans were taming aurochs about 10,000 years ago. They were massive, ferocious wild animals. But over thousands of years, domesticated aurochs became the cows we know today.
We think ancient humans had lots of reasons to domesticate those fierce aurochs. They probably used all parts of an aurochs for food and crafting. They used aurochs meat, hides, bones and horns. Plus, aurochs were super strong. A big domesticated animal could carry or pull stuff for humans.
This is a reconstruction of what an aurochs (left) looked like, based on real skeletons, and a picture of Holstein-Friesian dairy cow (right). That’s the most common dairy cow in the United States. These animals are related in the same way wolves are related to golden retrievers. Jaap Rouenworst CC BY-SA 3.0, Keith Weller/USDA
Much later, humans developed specialized breeds by selecting cows with different traits. That’s how we got dairy cows.
Ancient humans also domesticated wolves. Over time, dogs became hunting partners and camp guards. That happened way before they domesticated aurochs. Eventually, we’d have dog breeds that do specialized tasks—like pest control, herding and looking cute in a bow tie.
But dogs probably didn’t make enough milk to justify making a dairy breed of dogs.
I guess their biology got in the whey.
Sincerely,
Dr. Universe