You can lead a cow out of the barn, but you can’t make her eat grass. If she’s never been on pasture, it may take her a few days to learn how to graze, a University of Wisconsin-Madison study suggests.

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Whether or not a cow has to learn how to graze has been the nub of a debate over how dairy scientists should design research geared toward the needs of pasture-based dairy farm operators. The UW-Madison’s approach has been to use cows from its regular research herd, which are raised and housed in barns. But some farmers question whether findings from those studies apply to their operations. They wonder if barn-raised cows will graze as efficiently as cows that have been grazing all of their lives.

With input from members of the grazing community, dairy scientist David Combs designed a study to find out.

“We’ve been working on a trial for about three years and it’s basically answering a very simple question:  Do cows have to learn how to graze? ” Combs says.

Most U.S. dairy cows are now kept in barns, but grazing has regained favor among farmers looking for more of a low-input management system. While the UW-Madison has stepped up its pasture-based dairy research, some grass-based farmers have urged the university to create a separate, grazing-based research herd. But campus researchers weren’t sure that made sense.

“It would obviously be more efficient to take cows from the main herd and use them in grazing research trials than to create two complete herds with all the land and facilities needed to support them,” Combs says. “But there was the nagging concern with taking a cow out of a barn, putting her on pasture, and being able to get useful, reliable research information for graziers.”

Combs’s study compared behavior and performance of barn-dwelling cows turned out on pasture for the first time in their lives to that of cows raised on pasture. In addition to measuring milk production, he used GPS devices to track their movement around the paddock.

“We found that there clearly is a learning curve,” Combs says. “Cows that had never seen a blade of grass had differences in performance relative to those heifers that had been exposed to grass as growing animals.”

Milk production dropped as much as 10 pounds per day for lactating cows newly introduced to a pasture, mostly because the newcomers didn’t eat as much when they first arrived, he reports. But they adapted quickly. By the end of the first week on pasture, milk production was essentially the same.

Cows that were new to pasture didn’t seem to understand why there were there, Combs says. When they first arrived, they tended to stand by the gate looking for a way back to the barn. Meanwhile, the pasture-savvy animals fanned out and walked as much as four miles a day. But within a few days, it all evened out.

“Over the course of a week, all the animals, whether they were experienced or not, walked about two miles a day.  The experienced ones kind of scoped the pasture out the first couple days and then became more efficient.  The heifers that had not seen grass, at some point figured out that they had to begin to eat and began to actually graze,” Combs says.

Combs says the study suggests that grazing research done with cows pulled from the main university herd and placed on grass should yield information that applies to pasture-raised cows—as long as the learning curve is taken into account.

“From a farmer’s perspective, this is probably the kind of common sense thing. If you put an animal in a new environment, probably you (should) provide some feed that they’re familiar with so that they can make that transition.  An abrupt switch causes stress and it takes a couple days for these animals to adapt to that environment,” Combs says.

For more information: David Combs (608) 263-4844