September 30, 2022
Fargo, US 60 F

Managing Mastitis Through the Dry Period

Image courtesy of Boehringer Ingelheim
DULUTH, Ga. (September 20, 2022) — Although your cows might be resting during the dry period, your dry cow protocol should be hard at work.
“The dry period should be a time of healing and regeneration for the mammary gland,” said Jen Roberts, DVM, Boehringer Ingelheim. “An effective dry cow protocol needs to target current intramammary infections and minimize the risk of new infections. If managing mastitis is your priority, hopefully the cows can prioritize rest and rejuvenation, rather than fighting off infection.”
Treating Current Infections
“Somatic cell counts are a long-standing marker of milk quality,” explained Dr. Roberts. “Many producers use a dry cow antibiotic tube to treat cows that could be contributing to an elevated bulk tank somatic cell count. We want to target current subclinical infections and cows that have had chronic intramammary infection throughout their lactation.”
Since 95% of infections at dry-off are caused by Gram-positive pathogens,1 Dr. Roberts recommends choosing a dry cow antibiotic mastitis treatment that protects against Gram-positive bacteria including Streptococcus (Strep) and Staphylococcus (Staph) species.
Selective dry cow therapy (SDCT), in which antibiotic treatment is only used to treat cows that have been identified with previous or current intramammary infections, is an alternative to blanket dry cow therapy. By using a more targeted approach, SDCT allows producers to cut back on antibiotic use and associated costs.
“If you think your operation might be a good fit for selective dry cow therapy, reach out to your veterinarian,” suggested Dr. Roberts. “Although many producers have found success with SDCT, it isn’t going to be plausible for every operation.”
Preventing New Infections
Nearly 60% of mastitis cases that occur during a cow’s lactation can be traced back to the dry period.2 Placing your focus on prevention procedures can help to minimize mastitis risk and work to maximize milk quality.
“There are two main principles of prevention,” stated Dr. Roberts. “We want to maximize and supplement the cow’s immune defenses, and at the same time, we want to minimize bacterial challenge from the environment.”
1 – Maximize and Supplement
At the end of a lactation, cows form a keratin plug — a wax-like substance that seals the teat canal. “It’s the cow’s natural defense mechanism,” said Dr. Roberts. “It serves as a physical barrier to outside bacteria, and hopefully works to prevent contamination of the udder during the dry period and ward off mastitis to ensure milk quality.”
The caveat here is that many cows don’t form a keratin plug until a few days or weeks after the initial dry-off, and some cows never form a keratin plug at all. In one study, more than 55% of cows that dried off while producing 45 pounds of milk still hadn’t formed a keratin plug 40 days into their dry period.3,4
 
Dr. Roberts recommends using an internal teat sealant to supplement or mimic the natural keratin plug. Internal teat sealants have been designed to provide a sterile, antibiotic-free physical barrier between the udder and its environment that lasts the length of the dry period.
“An internal teat sealant should be administered immediately following a dry cow tube, if a dry cow tube is being used,” instructed Dr. Roberts. “The teat end needs to be thoroughly sanitized before infusion. Without proper hygiene and preparation, bacteria on the teat end may enter the udder and cause infection.”
At freshening, it’s important to strip the cow until all of the teat sealant is removed. If it’s not properly stripped, producers can end up with teat sealant residue in milk or milking equipment. Consider using a colored internal teat sealant, like blue, making it easy to distinguish from milk.
2 – Minimize Bacterial Challenge
Good animal husbandry is central to cow comfort, and cow comfort is an essential part of reducing environmental risks for mastitis.5 Consider these key management practices:
  • Bedding management. Remove manure as soon as possible and keep plenty of fresh bedding under cattle so udders remain clean and dry.
  • Heat abatement. Helping dry cows stay cool is just as important as keeping lactating cows cool. Dairy cows can experience heat stress beginning at 68 degrees F. Provide dry cows with proper shade, fans and sprinklers.
  • Ventilation. A well-ventilated building prevents high humidity in the winter and heat buildup in the summer. Signs of poor ventilation include air that smells like ammonia and animals that are coughing or experiencing nasal discharge or open-mouthed breathing. A cow’s hair coat should be free of moisture when you run your fingers through it.
  • Stocking density. Dry cows require significantly more space than lactating animals. To ensure dry cows have enough space to eat and rest, keep stocking density at or below 85%.
  • Nutrition.  Adopting a negative dietary cation-anion difference (DCAD) diet can help reduce the risk of subclinical hypocalcemia. Studies have shown a DCAD diet results in increased dry-matter intake in early lactation, increased milk production, fewer fresh cow health events and improved reproductive performance.
“What really matters here is, yes, having a protocol that sets cows up for a successful lactation, but it’s also about doing our part to ensure we’re delivering a high-quality product to consumers,” concluded Dr. Roberts. “Ultimately, a quality product is going to come from healthy, well-cared-for animals housed in a clean environment.”
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