"There doesn't appear to be a cap yet on the projections," says Nigel Cook, a dairy expert at the University of Wisconsin's School of Veterinary Medicine. Even though cows are producing 23,000 pounds per year on average, some herds produce more than 30,000 per head -- and he's found exceptional animals that can produce between 45,000 and 50,000. If more cows can be brought up to that level, the line could keep moving upward for a good while yet. Unlike poultry, for example, the state of dairy science isn't anywhere near maturity.
"We learn new things about dairy cows almost every day," Cook says. "I never thought I'd see cows producing 200 pounds of milk a day. That was beyond my ability to imagine 20 years ago."
So, what's happened to make cows so incredibly productive? For one thing, Cook says, farmers are feeding them excellent food -- the best alfalfa and other forms of grass silage. For another, they've been bred to be healthy and long-lived, not just walking milk pumps.
"There was a big focus on production, but we didn't focus on how they looked and survived and walked and how they milked," Cook says. "Instead of production indices, there's a much greater focus on cow survival, traits that allow her to stay in the herd longer." For a farmer, that's more valuable than a heifer that hits peak production and then needs to be replaced.
The final factor is environmental: Happy cows produce more, so he teaches farmers to coddle them. "Putting the cow in a very comfortable environment where she can rest for half the day, and she has all the things she needs to be a cow," Cook says. Deep sand beds to lounge on, for example, and heated barns when it's cold outside. "Basically she gets to live on a beach all day."
"They have a metabolic rate that's their equivalent of Lance Armstrong doing the Tour de France," Cook says. "They're like Olympic athletes, and we have to treat them like that."
It's a good thing cows are producing more, too, and that the world requires fewer of them. Cattle generate a lot of carbon dioxide and its equivalents, like methane, which contribute to global warming. Cook says they've already managed to reduce the amount of greenhouse gases produced per kilo of milk to a third of what it used to be -- and super-productive cows will only keep driving it down further.