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The role of recycled bedding in milk quality

Robert Plank for Progressive Dairyman Published on 06 November 2017
cows rest on reclaimed sand

Quality milk starts with quality bedding. Bedding is a point of exposure for vulnerable teat ends and a reservoir of growth for the bacteria that cause intramammary infections and subsequent spike in somatic cells.

A somatic cell count (SCC) of greater than 200,000 cells per milliliter is considered evidence of subclinical mastitis, and bulk milk somatic cell score has been found to vary depending on bedding type and management. Dairy producers seeking to troubleshoot a high SCC and improve milk quality should consider the role of bedding from both a materials and management perspective.

Several researchers have documented the association between bedding materials and mastitis-causing pathogens such as streptococcus, staphylococcus, mycoplasma, klebsiella and Escherichia coli.

Moisture, heat and food (organic matter) are the three life-sustaining requirements of bacteria; take any one away, and the ability of mastitis-causing organisms to survive will be significantly reduced.

Keeping bedding clean and dry is the first step toward preventing mastitis, reducing SCC and improving milk quality. This can be especially challenging for operations bedding on recycled sand or dried manure solids (DMS).

Sand has long been considered the gold standard in dairy bedding. Inorganic, cool and comfortable, sand conforms to the cow’s body, provides traction and drains away liquids. It is also continually kicked out of the stall and must be frequently replaced.

Researchers at Iowa State University recommend a minimum bedding requirement of 52 pounds of sand per cow per day. To ensure a sustainable supply of clean bedding, most dairy farms have systems in place for mechanically separating, washing and drying sand to remove as much organic matter and moisture as possible.

Common mechanical conditioning practices include repeatedly moving and windrowing recycled sand with payloaders or using vibrating screens, such as those developed for the mining industry, to physically shake water loose from sand particles.

When combined with effective separation, these drying methods can reduce moisture content in reclaimed sand to approximately 10 to 12 percent and organic matter content to 2 percent or less.

Some sand conditioning systems are more elaborate. Kinnard Farms, a 7,000-head dairy in northeast Wisconsin, beds its large-framed Holsteins exclusively on reclaimed sand in barns gravity-flumed with recycled water.

While cows are being milked, the sand-manure mixture is scraped into a central flume three times a day and carried to a dedicated processing building, where sand is separated by augers, washed with recycled parlor water from a separate tank system and passed over a vibrating screen.

Until recently, the final step involved moving the clean sand several times to allow it to air dry, which yielded a moisture content of about 10 percent but required considerable resources in the process.

“Air-drying our sand took a lot of fuel, machinery and manpower,” co-owner Lee Kinnard says. “Fortunately, we found a better way.”

Sand dryer installed

In 2016, Kinnard Farms became the first dairy operation in the U.S. to install a dedicated bedding dryer system. The Kinnard family worked with engineers, designers and company representatives to install the dryer on top of newly poured cement piers inside the farm’s new sand recycling building, then positioned the augers, cyclone and airlock, and connected the various motors to the control room.

High temperatures in the bedding dryer quickly reduce moisture

High temperatures in the bedding dryer quickly and efficiently reduce moisture and kill pathogens responsible for causing mastitis and poor milk quality.

Kinnard says the new dryer has allowed the farm to reduce the moisture content of its sand to about 2 percent, creating a virtually endless supply of clean, dry and comfortable bedding.

“The bedding dryer pretty much completes our vision of hands-off sand recycling,” Kinnard says. “It’s a pretty cool technology that fits nicely into our entire sand management system and allows us to achieve a level of sustainability unimaginable only a few years ago.”

Manure drying strategies

Producers bedding on dried manure solids may also wish to consider new drying technologies in their quest to reduce moisture and improve milk quality. Studies have shown higher bacterial counts on teat skin for cows housed on organic bedding compared to sand, and University of Wisconsin researchers reported farms bedding on manure had a higher average bulk milk somatic cell score than farms using sand or non-manure organic material.

However, when good manure management practices are followed, the economic benefits of using a readily available bedding material can outweigh potential concerns about udder health and milk quality.

Cornell University reported that the use of mattresses topped with a 2-inch layer of DMS can reduce average bedding moisture content over farms using deep beds, possibly because manure solids in deep beds tend to mat together from the weight of the cow while DMS on mattresses either fell off or spread out.

They also found DMS was drier in stalls bedded weekly compared with stalls in which fresh manure solids were added daily.

Other manure drying strategies include windrowing or piling for several days, running solids through a roll press or screw press, or putting solids through a drum composter. As with recycled sand, a bedding dryer can be used to reduce moisture and pathogens in recycled manure solids.

The unit currently used to dry recycled sand at Kinnard Farms can be configured to process up to 18 tons of manure per hour, delivering a moisture content of up to 50 percent without the need for labor-intensive mechanical conditioning.

A clean, dry resting environment is far less likely to harbor mastitis-causing bacteria which can cause infection, elevated SCC and reduced milk quality. Optimizing moisture removal not only reduces these risks but also helps dairy farmers more fully realize the economic and environmental benefits of using recycled materials.

“Dairy farmers are the original land stewards,” Lee Kinnard says. “By finding new and better ways to recycle and dry our bedding, we’re ensuring a more sustainable operation for the next generation and higher milk quality for everyone.”  end mark

PHOTO 1: Cows rest on reclaimed sand.

PHOTO 2: At Kinnard Farms, high temperatures in the bedding dryer quickly and efficiently reduce moisture to about 2 percent and kill pathogens responsible for causing mastitis and poor milk quality. Photo courtesy of McLanahan Corporation.

References omitted but are available upon request. Click here to email an editor.

Robert Plank is the global product manager – agricultural products with McLanahan Corporation. Email Robert Plank.

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