Cow Comfort Innovations in the barn

Published on Fri, 02/20/2009 - 10:34am

"If somebody develops a new thing," says Kevin Janni, "and it works, I'm very willing to describe it." But first, says the University of Minnesota professor of Biosystems and Agricultural Engineering, he wants to see that it works-and the first time around, he may not be entirely sold.
The phenomenon of compost dairy barns provides an example. A Minnesota producer came up with the idea in 2001. "They actually talked to us before they did it," Janni laughs, "and I was not enthused.
But the local Extension educator stayed in touch with them; some other people here on campus worked on the bedding and they got it going, and we decided that there's lots of interest in it, and so we started making presentations."

Janni estimates there are now 50 compost dairy barns in Minnesota, and a few more in Wisconsin.

Instead of freestalls, a compost dairy barn has an enclosure with 3' concrete walls, and two driveways to provide cows access. The producer lays down sawdust or another bedding, and stirs it twice a day. "The cows lay down in there," Janni explains, "and eat from the regular manger area like a freestall barn." In 2007, MU hosted a conference on the barns that drew attendees from seven countries. But Janni adds, "It's going to be a little bit of a niche market; I doubt that a producer of 500 cows is going to use one of those, other than for their transition cows and hospital area. It's not going to replace freestalls, but it's a very cow friendly housing system."
Low-profile cross-ventilated (LPCV) barns provide another example of a producer innovation that's caught on within the industry. A Kansas State University Extension specialist is credited with coming up with concept six years ago; as Janni puts the story (which he admittedly heard second-hand), "An innovative producer wanted to come up with something, and then they laid it out on a napkin in a coffee shop, I guess, and they built it-off they go." Janni describes an LPCV barn as looking like two or three naturally ventilated freestall barns built side-by-side, but with a low, flat roof, like a warehouse. "The air enters one side of the barn," he says, "and fans are in the walls along the other side of the barn; the air then goes across the building.The other element that's critical-they have baffles that come down from the ceiling over the freestalls, so that the air is forced to come flowing back down, close to the cows. These barns will often have some kind of an evaporative cooling system; they may have evaporative pads."
Janni has seen an LPCV barn that used high-pressure sprayer nozzles for evaporative cooling. "So," he says, "the air comes in in warm weather, is cooled evaporatively, goes across the barn and out the far side and that's all mechanically ventilated." The low roof helps keep the energy cost down; there's been some research on the comparative energy use of LPCV barns, naturally ventilated freestall barns and compost dairy barns. Janni's colleague in the MU Department of Animal Science, Dr. Marcia Endres is collecting environmental and cow locomotion data. When all the fans in an LPCV barn are engaged, they can consume a lot of energy. "Basically," says Janni, "the one wall is fan next to fan next to fan, and they are 48" or 52" diameter fans, the whole length of the barn.
I'd raise the question whether we need to move quite that much air, but that's the current practice, and I haven't got any documentation to tell people we don't need to do that." But he notes many naturally ventilated freestall barns already utilize mixing fans, which create drafts across the cows' backs. "If you're going to build this barn and put all these mixing fans in there," Janni asks, "why not put them in as ventilation fans, and lay it out in another way?"
The big question, obviously, is whether they pay off for the producer, and a 2008 study by Kansas State University would seem to answer in the affirmative. The K-State scientists estimated the more moderate temperatures in the LPCV barn would increase productivity by 1,000 lbs/cow/year; taking into account increased energy and feed costs, the low-profile cross-ventilated barn would yield a $115/cow higher return per year than a traditional, naturally-ventilated freestall barn. "Even if LPCV barns require a larger initial investment per cow ($500 or more)," they concluded, "they are still more profitable than the naturally ventilated barn when costs are spread over the useful life of the investment."
Janni says a small study conducted in Wisconsin appears to confirm the K-State report. The researchers took a formerly naturally ventilated barn and modified it, putting in one baffle and a pressure sprinkling system in addition to cross-ventilation. "They saw an improvement in milk production between one year and the next year," he says. "The ketosis went down. The producer was very, very happy with it. Clearly, if it wasn't paying for itself, people wouldn't be doing it."
To the mechanical ventilation equipment, which brings outside air into the barn to promote cooling, the producer can add evaporative pads, or high- or low-pressure sprinklers. "In a naturally ventilated barn in the summertime," says Janni, "the driving forces causing air flow are two factors. One is wind; the other is thermal buoyancy. Warm air rises; moist air rises." But in warm weather, the air inside the barn is the same temperature as outside, and a naturally-ventilated barn is reliant upon wind, which is highly variable and comes from different directions. "So, there are periods of problems in very hot weather when it's hard to get a lot of air exchange, so it can be pretty warm. That's where the mixing fans, or a cooling system, come in."
In either a low-profile cross-ventilated or tunnel ventilated barn, the fans are controlled to run for at least a minimum amount of time, and a thermostat will trigger increased air flow as needed. Although sprinkler systems are sometimes operated manually, the cooling pads in a LPCV barn are automatic. "Water that is added at the top goes down," Janni says, "and as the air passes through, it evaporates some of the water; in the process of evaporating water, the air temperature decreases." They're most effective in a dry climate; in already humid environs, the increased evaporation adds to the cow's discomfort. In these areas, low-pressure systems are preferred; they're placed in the holding area or manger, and the sprinklers wet the back of the cow. "The heat from the cow evaporates the water,"
Janni says, "so that's like an 'artificial sweating' kind of a system." Because you don't want to wet the cow continuously, the sprinklers are put on an automated timer, giving them a few minutes to dry off before they trigger again.
Jannie concludes, "The use of fans clearly has increased as we've seen producers put in tunnel ventilation as an option, and new low-profile cross-ventilated barns. The use of mechanical ventilation is way up, and is giving the producer a lot more control of that environment."

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