eli5 Why do cows produce so much milk while pregnant? Instead of producing milk only after birth to feed their young? Does it have to do with the fact that they’re pregnant every year so their body is trying to produce milk for their previous offspring?

Question

eli5 Why do cows produce so much milk while pregnant? Instead of producing milk only after birth to feed their young? Does it have to do with the fact that they’re pregnant every year so their body is trying to produce milk for their previous offspring?

In: Biology

Answer 1

They’re bred that way. The amount of milk dairy cows produce has increased over threefold since the middle of last century. A dairy cow can produce 30-50 liters per day, which is way more than the 4-5 liters a calf needs per day.  We created cows that overproduce milk the same way we bread sheep that overproduce hair and turkeys that overproduce meat. Dairy cows have to be milked twice a day or they are in massive pain. Sheep need to be sheared once a year otherwise they disappear under their wool.