When temperatures climb and humidity hangs in the air, somatic cell counts (SCC) often follow suit. The added stress of hot weather can weaken a cow’s immune defense, opening the door for mastitis and setting the stage for SCC levels to spike.
While you can’t control the weather, you can take control of the situation. Amber Yutzy, assistant director of animal system programs at Penn State, and Emily Krekelberg, extension educator at the University of Minnesota, share practical strategies to help keep SCC levels in check all summer long.
Heat Stress Headaches
“Somatic cell counts tend to rise with temperature and humidity levels during summer,” Yutzy says. “Environmental stress caused by the high summer temperatures are responsible for the elevated counts. These higher somatic cell counts can stick around on your farm for weeks or months.”
Yutzy explains cows are simply more vulnerable when the heat sets in.
“We often see decreased production during hot weather because cows spend more time standing or lying where it’s cooler and less time eating at the bunk,” she says. “Environmental mastitis also increases during this time because of more frequent exposure of the teat end to bacteria.”
Add stress to the mix, and the immune system takes a hit.
“Research has shown high circulating levels of stress hormones interfere with the ability of the immune system to destroy bacteria. When bacteria enters the udder, the cow’s immune response sends somatic cells to fight back. But stress hormones depress the function of those cells — weakening the defense against mastitis-causing organisms.”
Even only a few problem cows can skew your bulk tank.
“Just a few cows with really high individual SCC can raise the entire bulk tank level,” Krekelberg adds. “Be sure to look at individual cow reports. This can help you pinpoint problem cows and potentially make culling decisions.”
Start with Cultures: Identify the Source
If your SCC is climbing, the first step is to identify the cause. That means culturing.
“Start with a bulk tank culture to find out if the problem is environmental, contagious or something else,” Krekelberg recommends.
Results will guide your strategy, but it’s best to test on multiple days. Sometimes, one aggressive organism overwhelms the plate and hides others. For a clearer picture, consider culturing individual cows with persistent high SCCs or new infections.
When It’s Contagious: Contain and Control
If the culture reveals contagious culprits like Staph aureus, Strep ag, or mycoplasma, you’ll need to implement aggressive containment.
“Contagious cows should always be milked last to avoid spreading the organisms to uninfected cows,” Krekelberg notes.
Krekelberg also advises housing infected cows separately and ensuring proper teat dip coverage, both pre- and post-milking.
“Pre-dip should have a contact time of at least 30 seconds with the teat skin surface,” she says. “Post-dip must fully cover the teat.”
She also stresses not overlooking the basics. Take time to assess how your milking equipment is functioning and review your cow prep protocol with employees. Regular inspections of liners, hoses and vacuum levels are essential to ensure optimal performance and prevent contamination.
When It’s Environmental: Clean, Dry, Repeat
If your issue is environmental, the goal becomes eliminating moisture and bacteria from the cow’s surroundings.
“Add more bedding to stalls or packs and change bedding more often,” Krekelberg suggests. “It could be worth it to bed twice a day if you notice cows are really getting wet and dirty.”
She also stresses keeping milking equipment clean and ensuring spotless teats before unit attachment.
“There should not be any dirt or manure present. Taking the time to clean teats thoroughly makes a huge difference.”
7 Steps to Help Lower Your SCC This Summer
Yutzy, along with British dairy vet Peter Edmondson, a mastitis and milk quality expert and owner of UdderWise Ltd., outline seven tactical steps to improve SCC — especially during high-risk seasons like summer:
- Keep bedding clean and dry. Humid summer air encourages bacterial growth. Maintain clean, dry stalls to limit bacterial exposure and encourage cows to lie down in stalls rather than in manure-laden alleys.
- Use fans and sprinklers wisely. While cow cooling is crucial, mismanaged fans or sprinklers can backfire by creating wet stalls, overly damp cows or congregation zones that collect manure. Aim to cool cows without compromising cleanliness.
- Control flies aggressively. Biting flies are more than just a nuisance —they’re stress-inducing vectors for mastitis-causing bacteria. A solid fly control program protects both herd health and productivity.
- Train the team. Reinforce milking protocols with all employees. Proper technique helps limit new infections and ensures early detection of clinical mastitis cases.
- Provide plenty of fresh, clean water. At 80°F, cows drink up to 50% more than they do at 40°F. Adequate water access is critical to help them cool themselves through increased respiration and perspiration.
- Stop the spread. Create a separate milking group for high-SCC cows and always milk them last. Use gloves and keep them clean. Whether you use paper or cloth towels, one per cow is the rule — no sharing. Replace cloth towels after 500 to 600 uses, and wash at high temperatures.
- Make a plan and track it. Edmondson stresses the importance of clear, measurable goals. Focus on cows contributing the most somatic cells to the bulk tank. Consider their history, production and treatment response. Don’t rush to cull. Instead, evaluate carefully with your vet. Most importantly, monitor progress monthly.
Stay Low on Purpose
Keeping somatic cell counts in check through the summer heat takes more than just good intentions. It requires a combination of sound management, consistent routines and close monitoring. By staying proactive and focused on the details, you can limit seasonal setbacks and protect your farm’s milk quality all year long.
“Having a low SCC never happens by accident,” Edmondson concludes. “It’s the result of high intention, sincere effort, intelligent direction and skillful execution.”
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