Dr. Jeffrey Bewley admits his first impression of compost bedded pack barns for dairy cows wasn’t favorable. He was concerned about animals laying on manure, impacts on milk quality and mastitis potential.

Bewley, who serves as executive director, Innovation and Genetics, Holstein Association USA, pursued the concept and realized that with good management, a compost bedded pack barn can be a great environment for dairy cows.

These barns are loose housing systems with large, open resting areas. “Cows add manure and urine to an organic bedding base (sawdust or wood shavings),” said Bewley, “then we till or stir it twice a day to manage the compost process.”

The concept is more than a continual process of putting bedding down and cows adding manure: it’s the intensive management of a compost process while keeping cows dry and clean. There’s a higher risk of mismanagement compared to stall-based barns and it’s less forgiving of poor management.

Although the pack must be stirred several times a day, that task doesn’t take long, and the process requires less labor than managing individual stalls. A pack that’s working correctly remains dry and clean. A properly managed compost bedded pack provides a dry resting surface that results in clean cows and clean udders – drivers of clean cows and milk quality.

“When the compost barn does not work well, there’s a higher incidence of clinical mastitis,” said Bewley. “There’s a higher somatic cell count, and more hairy hill warts or digital dermatitis. It matters that we’re providing a dry resting surface.”

A bedded pack barn is cleaned less often and there’s less total volume of material to remove. The material maintains more nitrogen when it’s composting properly and is more nutrient-dense when field-applied. Odor and fly reduction are additional benefits.

Compost bedded packs have several animal welfare benefits. Cows can rest in different positions and fall easily into deep sleep, which may result in positive behavioral and immune function benefits.

“We see more play and dominance behavior in compost bedded pack barns and that’s probably an advantage,” said Bewley. “Cows [on a pack] have a much smaller flight zone. I think that’s because they have better footing and can walk away easily. It’s a lot easier for cows to lie down or rise from resting without the restrictions associated with freestyle barn loops. Cows walk into a compost barn and there isn’t hesitancy to lie down.”

Cows in bedded pack barns exhibit estrous well, which Bewley attributes to secure footing. There’s less lameness and better locomotion scores. Multiple breeds of different sizes can be housed in the same barn.

One negative of a bedded pack barn is availability of sawdust or shavings. “We need an organic bedding source for carbon,” said Bewley, adding that sources for sawdust and shavings aren’t always reliable or economical. “There’s a higher variable cost associated with the compost bedded pack barn because it uses more bedding.”

Bedding adds carbon and absorbs moisture from manure and urine. Sawdust and shavings with moderate particle size are ideal. Ground straw, corn cobs or soy stubble are suitable, but none of those are easy to obtain regularly. Rice hulls add porosity but lack carbon and moisture absorption capacity. If a compost barn is excessively moist and not functioning properly, the best solution is adding sawdust.

A common mistake is not putting enough bedding in when the pack is started. Bewley recommends a least 12 to 24 inches of shavings or sawdust to start.

“People expect it to work immediately, but a population of bacteria has to build,” he said. “It takes three to four weeks before it really starts composting. It isn’t going to happen overnight.”

Adequate pack mixing is critical. Bewley suggested equipment that includes shovels or sweeps for better mixing. Ideally, equipment has rototiller action to work deep into the pack.

The optimum pack barn set up allows stirring in multiple directions or in circles. This helps increase air infiltration and can break up clumped material. Barns should be designed with minimal posts to allow easy equipment movement for thorough mixing.  Stirring equipment that’s too heavy can compact processed material, which results in restricting the oxygen necessary for optimal composting.

While the pack may appear to be “working” when there’s visible steam, it isn’t a guarantee of compost action. Although steam is a good sign, Bewley said it usually indicates the pack is warmer than ambient conditions.

He suggested management checks to determine whether aerobic action is present. The internal temperature at eight to 12 inches deep should be 110º to 150º F, or just hot enough that it can barely be touched.

Moisture is a leading indicator of proper microbial action in the pack. However, it isn’t easy to measure moisture content. Some farmers use soil probes to gauge moisture, but such tools are designed for a specific density and don’t provide an accurate measure of moisture.

Bewley recommends the “ball test,” which involves taking a wad of compost, forming a ball and squeezing it. If water comes out when the ball is squeezed, the pack is too wet.

Assessing the degree of dirt or manure on cows isn’t a good indicator because the pack has already been too wet. High SCCs or clinical mastitis are signs it isn’t working.

Good pack management also involves milking hygiene. “Focus on the teat ends when you’re cleaning in the milking parlor,” said Bewley. “It’s important to think about parlor hygiene and milking procedures. Not all mastitis comes from the cow’s environment or how clean the cow is.”

Bewley said peroxide pre-dips do not work well in compost pack barns. “I think there’s just too much organic load for peroxide to be able to handle,” he said, “and we always want to think about genetic selection for mastitis risk.”