美国国家公共电台 NPR As Milk Production Cools In Summer, Farmers Try To Help Cows Take The Heat

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SCOTT SIMON, HOST:

Climate change disrupts our lives in all kinds of ways, including in the icebox. It turns out, global warming is hurting global milk production. As part of our summer series on heat, Mose Buchele of member station KUT has this.

(SOUNDBITE OF CICADAS CHIRPING)

MOSE BUCHELE, BYLINE¹: The morning I visit Mill-King dairy farm in McGregor, Texas, the cicadas are loud, but the cows are silent.

CRAIG MILLER²: It's starting to warm up, so they're starting to get a little bit less frolicy (ph).

BUCHELE: That's Craig Miller. His grandfather started this farm. Now he runs it. And hot cows are exactly what I've come to talk to him about.

MILLER: Any dairy farmer - commercial, small, local - are experts in dealing³ with heat.

BUCHELE: That's because the way cows digest food takes a lot of energy and generates a lot of heat. When it gets too warm outside, cows want to cool down, So they spend their energy panting, increasing blood flow to their skin and...

MILLER: They just stop eating. It's hard to get feed into them.

BUCHELE: In the case of beef cattle, that means less beef - with dairy cows, less milk.

MILLER: Right now, this time of year, you just expect in any farm in Central Texas, it will produce about two-thirds of the milk they will in January.

BUCHELE: That means less money for his family business. And Miller says he's noticed summers are getting longer and hotter. So you can see the problem. One study finds the nation's dairy industry already loses $900 million a year thanks to what it calls heat stress. Another says global warming has already decreased U.S. milk production from Holstein cows by about 2 percent. Geoffrey Dahl is the chair of the Department of Animal Sciences at the University of Florida, Gainesville.

GEOFFREY DAHL: There are a lot of cows that are going to be living in hotter climates, and that number's probably going to increase in the future.

BUCHELE: And the problem is bigger than just hotter summers. Dahl's research shows how pregnant cows that suffer heat stress give birth to calves⁵ that also produce less milk.

DAHL: It's kind of a negative cascade⁶ that occurs from those early - well - in utero, really - insults.

BUCHELE: He and his colleagues are working on one solution. They've bred a new kind of dairy cow. It includes the DNA⁷ of a South American cow breed that's adapted to better withstand heat. It's called a slick cow.

DAHL: That's really in reference to their hair coat. They have a very, very fine hair coat, and that's all part of their improved ability to handle higher temperatures.

BUCHELE: He says these cows also seem to sweat more and transfer heat off their bodies more efficiently⁸, so their milk production does not decline when it's warmer out. Heat-tolerant slick cows just went on the market about six months ago.

DAHL: There are actually some bulls now that are available through a couple of the semen companies out there that have this slick gene⁴.

BUCHELE: Meanwhile, other researchers are looking at more traditional techniques to help cows cope with the heat.

BARBARA JONES: We have fans here, and we also have sprinklers.

(SOUNDBITE OF SPRINKLER)

BUCHELE: Barbara Jones directs the Southwest Regional Dairy Center in Stephenville, Texas, where 400 cows are milked, studied and kept cool. They munch⁹ on feed in their barn while pipes overhead spray them with water.

(SOUNDBITE OF WATER SPRAYING)

JONES: It should wet the cow to her skin. Then those sprinklers will shut off, the fans will keep going, and we're going to employ that evaporative cooling to cool the cows.

BUCHELE: Jones is researching what different dairy farm designs and cooling techniques do to milk production. She says these water and fan setups are pretty common in the South and Southwest, but they could be used more. Geoffrey Dahl at the University of Florida says they're also becoming more widely used in other parts of the country as those places get hotter.

(SOUNDBITE OF CICADAS CHIRPING)

BUCHELE: Back at Mill-King dairy farm, that doesn't surprise Craig Miller. But he points out that all of these things cost money.

MILLER: You know, there's only so much that you can do and be economically feasible.

BUCHELE: That could mean yet another consequence of a warming climate - more expensive milk.

(SOUNDBITE OF COW MOOING)

BUCHELE: For NPR News, I'm Mose Buchele in Austin.