Clinical mastitis is an ongoing problem on almost every dairy. We know what causes it, but prevention is another story, according to Dr. Nigel Cook, a professor at the University of Wisconsin. In his experience, around 15 percent of cows on dairies have clinical mastitis, but Cook sees opportunities to reduce that incidence with proper barn design and management.
“We do a lot of things right,” Cook said. “The dairy industry has really been trying to be progressive and move forward, but one area where I think we continue to struggle is clinical mastitis.”
In his presentation at the National Mastitis Council Annual Meeting in St. Pete’s Beach, Florida, this past January, Cook said the cow’s living environment plays a major role in the cow’s udder health.
He explained that reducing environmental mastitis hinges upon keeping the udder and teat area free from bacterial contamination between milkings. That boils down to three things: indexing by design, managing bedding and maintaining the stall microclimate.
1. Indexing by design
Indexing can be defined as telling the cow just enough, but not too much, where to lie and then giving her the space to be comfortable. A properly indexed stall is important for reducing mastitis risk because it will encourage the cow to defecate in the alley, as opposed to in the stall where teat ends are susceptible to bacteria.
“You need to know your stall anatomy because stall loop design will help you place the cow in that stall and it really is about that lower bar,” Cook said. “You want to make sure that cow doesn’t trap her leg below that bar, so we’re going to leave about 5 inches between the top of any brisket locator and the bottom of that bar. That will avoid entrapment. We’re going to put the top of that bar at about 12 inches above the stall surface or the rear point of the curb if you’re in a deep, loose-bedded stall. It’s high enough to prevent the cow from getting up inside the loop or putting her leg over the top, but not so high that it gets in the way of the normal movement of the cow’s head.”
The bar angle should go past the brisket locator by about 20 to 22 inches. The openness of the loop or its diameter is where the neck rail should go, height wise. From there, adjust the neck rail’s distance from the rear curb to give the cow plenty of room while still keeping the stall clean.
The cow should always lie down straight, not diagonally. Proper setup of the front portion of the stall is critical to accomplishing this goal.
“We know cows don’t like stalls with big ugly brisket locators, and the reason they don’t like them is because they really want to launch their front legs forward as they rise,” Cook said. “We see that on pasture. We want to replicate that in a stall. They can’t lift their leg much higher than about 4 or 5 inches above the stall’s surface, so when we put an 8-inch piece of wood in the way, it’s an obstruction. Cows do not like it.”
At the same time, brisket locators are necessary; otherwise, the cow does not know where to lie in the stall.
“When we build big, spacious stalls, comfortable stalls for cows, we say ‘Let’s get rid of the brisket locators.’ They kind of turn into a mess because there’s no way to place that cow on the platform, so we need some kind of location device,” Cook said.
Some dairies are trying out a concrete brisket slope, which helps to position the cow in the stall while still allowing it to lie with a front leg outstretched. The cow is also able to plant a front foot while rising, thus pushing it backward in the stall.
The front beam in the stall should allow the cow room to lunge, but deter it from walking through the front of the stall. The beam should be level with the top of the cow’s head when lying down, so it is out of sight. He said this is typically between 36 and 38 inches from the bottom of the stall.
Finally, it is important to size stalls to accommodate cow size. This means that on average, Holsteins need a 10-foot stall.
2. Bedding management
According to Cook, sand is the gold standard for bedding. Cows have the highest lying times on sand and it leads to higher milk production and a lower SCC. However, since the stall does not have a base and cows like to dig holes in the deep, loose bedding, thus altering the stall setup, it can become a gathering ground for mastitis pathogens. To help with this, Cook suggested leveling beds and removing wet bedding daily. He said most dairies fill and redistribute the bedding twice a week, but he likes to see that happen a little more frequently.
Sand reclamation is feasible, but to be successful with it, the farmer needs to choose the right type of sand for their particular system and make sure the sand going back in the stalls meets the standards for dry matter, organic matter and bacteria counts, Cook added.
In addition, farmers need to keep a close eye on the compaction zone. When it gets close to the rear curb, move the soiled material and refresh the bedding.
For those using manure solids, Cook said they still need to maintain a dry, level bed.
3. Stall microclimate
To a degree, Cook said each cow’s stall is a microclimate. It is critical that whatever bedding used in the stall is under 30 percent moisture. When the cow lies in the stall, she traps heat, incubating any bacteria in the bedding.
“Cows that are lying down accumulate heat. They do so fairly rapidly, about a degree Fahrenheit per hour,” Cook said.
To stay cool and keep the bacteria count down, cooling and ventilation are key.
“Cows like fast-moving air when they’re heat stressed. I’m going to suggest that’s fast-moving air at around 400 fpm, 4.5 miles per hour, 2 meters per second – whichever your preference is,” Cook said.
He later continued, “We’ve realized that a lot of the fan spacings we had were incorrect. They didn’t optimize the distribution of that fast-moving air over the cows in the resting space, so we’ve started to move these fans a little closer together.”
He said he’s seen good results with fans spaced 24 feet apart where the air was redistributed to as many cows as possible. In cross-vent barns, he recommended adding baffles to encourage fast-moving air in the resting space. Curtains are a good option, he said, since the baffle height can be adjusted. This way, air does not get trapped during the winter and it limits air exchanges per hour.
Air movement, he added, needs to be a major focus when designing any barn. In the summer, there should be at least 50 air exchanges per hour.
“At the same time, those facilities have to ensure sufficient air changes per hour,” Cook said. “We have to get air in and out of that barn to get the heat exchange, to get that heat and moisture out of that facility, least it get trapped in there and influence the environment of the cow.”
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PHOTO: “We know cows don’t like stalls with big ugly brisket locators, and the reason they don’t like them is because they really want to launch their front legs forward as they rise. We see that on pasture. We want to replicate that in a stall,” Dr. Nigel Cook said. Staff photo.