Building Bessie a better bed

St. Paul, Minn. — Minnesota is home to more than 5,000 dairy farms, and most have fewer than 100 cows. Many of these herds are housed in older facilities that are often less efficient than larger, more modern dairies — a competitive disadvantage. That’s one of the reasons Minnesota is losing about two dairies a day.

Finding an economically-viable way to modernize could help these small operations survive. A new, innovative cow-housing system with lower construction costs, reduced labor inputs and improved cow comfort could help solve some manure-management issues that small farms face.

Compost-bedded-pack dairy barns are open facilities with bedding, typically sawdust, which is several feet deep. Cows lounge on the thick pack that farmers till or stir several times a day. Microbial activity causes the manure and bedding to compost, creating warmth for the cow and stabilizing the manure. It also reduces pathogens and is good for cows’ health.

But rising fuel prices have increased the cost of transporting sawdust and wood shavings commonly used in compost barns. Tight wood-product supplies also impact availability.

Since wood is only one source of bedding, AURI and the University of Minnesota investigated other locally-available products to find an alternative.

“Farmers have used straws and corn stalks for bedding for many years,” says Al Doering, who heads AURI’s coproduct lab in Waseca. “We wanted to see if there were ag products out there that could work for compost barns.”

Researchers at the U of M St. Paul campus tested 11 different media for chemical, physical and microbiological characteristics that would indicate they could be used for bedding. They tested beet pulp, corn cobs, corn stover, elm chips, flax straw, pine bark, pine chips, soybean hulls, soybean straw, wheat straw and wheat-straw screenings. They evaluated the various products for pH, water holding capacity, carbon to nitrogen ratios, phosphorous, bulk density and free air space, which is needed to support microbial activity.

For various reasons, many of the products tested were not suitable for composted pack barns.

“We know a lot more than we did two years ago, but we still don’t have all the answers,” says lead researcher Tom Halbach of the U of M soil, water and climate department.

Halbach says there were significant differences between many of the products tested, and not all were suited for compost barns. For example, corn stalks absorbed water, but once the cell wall was ruptured, water was released, leading to a wet mess. Soybean hulls and beet pulp didn’t work either. Only one product looks to be viable, Hallbach says.

“Corn cobs worked because they’re light and airy, are low in carbon and are easy to handle,” Hallbach says. “But the difficulty with corn cobs is it’s difficult to find a supply … we’d likely have to modify (corn) harvest techniques.”

Flax and soybean straw showed potential, but would have to be blended with sawdust or small wood chips.

“We’re on the right track,” Halbach says. “We had some options and found out that some didn’t work.”

“Because of the growing interest in compost barns and the demand for bedding material, this really provides an excellent opportunity to utilize ag fibers and coproducts,” Doering says. “Not everything we looked at worked; it helps to narrow down other alternative sources that could be available to dairies.”

Four different media are undergoing more tests at the West Central Research and Outreach Center in Morris, Minn. including sawdust, a blend of sawdust and small wood chips, corn cobs and soybean straw.

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