CSI-Dairy: E. coli mastitis
A cow-side investigation into E. coli mastitis: A wolf in sheep’s clothing
Numerous ‘culprits’ on dairy farms combine to rob herd performance and injure a dairy’s bottom line. Identifying and arresting the offender isn’t always easy, and often requires a full investigation, gathering and analyzing evidence on the farm and in the lab.
By Jeramie Voss
I don’t work closely with Dave Johnson, a dairy producer a few towns over, but when his herd veterinarian asked me to help look into some milk quality issues, I was happy to help. The 1,000-cow dairy usually maintains a low somatic cell count (SCC), but he was concerned because recently it was climbing to the 300,000 cells/milliliter mark with little explanation.
I began my investigation. After talking with the team, observing in the milking parlor and digging into the dairy’s records, I uncovered a few issues that needed attention.
You can’t find what you don’t seek
The lack of a consistent mastitis culturing program on the dairy operation was a concern. The on-farm culturing program was discontinued nearly a year earlier. The managers assumed they knew which mastitis-causing pathogens were on the dairy. That also meant the farm’s mastitis treatment protocols were based on outdated records, and the drugs no longer matched the bugs. The veterinarian reinstated the culturing program, keeping in mind that sampling is a surveillance effort to look for contagious pathogens.
A few guidelines:
• Sample clinical cases to identify pathogens and plan treatment decisions.
• Sample all fresh animals to uncover any pathogen exposure during the dry cow period.
• Perform periodic bulk tank sampling to determine whether contagious pathogens are present.
• Sample purchased cattle to ensure cows aren’t bringing new infections into the herd.
Early culture results showed up to 75% of the dairy’s mastitis infections were caused by Escherichia coli (E. coli), a Gram-negative pathogen. The intramammary tubes used in the past to treat mastitis weren’t effective against Gram-negative mastitis, leaving the cows virtually untreated for E. coli mastitis and damaging milk quality and overall wellness.
Dave was astonished. He couldn’t believe his cows had E. coli mastitis, especially since his milkers classified most of his mastitis cases as mild Grade 1 or moderate Grade 2 mastitis, in which cows are not sick or off feed. How was this possible, he asked. To him, all E. coli mastitis was nasty and really took a toll on cows. I explained that not all instances of Gram-negative infections are severe and that a majority of Gram-negative infections are just typical, everyday, run-of-the-mill mastitis. This is why having a culturing program and maintaining records are so important.
Keep the bugs at bay
Armed with the culture records, we looked at ways to minimize exposure to Gram-negative bacteria. As an environmental pathogen, E. coli, if present on the dairy, is found in manure and water throughout the farm environment. Properly managing bedding and free stalls is critical to limiting pathogen exposure. We paid special attention to misters and soakers to ensure water didn’t pool in bedding and create a utopia for E. coli infection. We also reviewed and evaluated the milking procedures and used proper pre- and post-dipping protocols to minimize contact with E. coli.
Mastitis incidence at freshening revealed another issue – most of the Gram-negative mastitis infections were within the first five days in milk. Dave’s dry off procedures did not include an internal teat sealant, leaving cows defenseless against environmental mastitis in the dry lot. We incorporated an internal teat sealant into his dry cow program to help limit exposure to bacteria and keep cows healthy at freshening.
Treating E. coli mastitis for a cure
Here’s the real problem: The treatment protocols didn’t properly treat Gram-negative infections. The herd veterinarian and I met with Dave to discuss his treatment protocols, in particular two important changes:
• Switching intramammary tubes to target the bug with the right drug
• Determining the appropriate duration of therapy to achieve a complete cure, or bacteriological cure
Based on recent research1, we developed a new extended therapy treatment protocol using an intramammary tube labeled to treat E. coli mastitis. With that switch, and the other management changes, the SCC gradually fell back to 200,000 cells/ml. Dave’s story reveals why we need to continually evaluate milk quality programs so we know what we’re dealing with and how to best attack problems.
1/Schukken YH, Bennett GJ, Zurakowski MJ, et al. Randomized clinical trial to evaluate the efficacy of a 5-day ceftiofur hydrochloride intramammary treatment on nonsevere gram-negative clinical mastitis. J Dairy Sci 2011;94(12):6203-6215.
• Jeramie Voss is a quality milk manager with Pfizer Animal Health and works with dairy producers to improve mastitis management.
• Contact your herd veterinarian or Pfizer Animal Health representative with questions about your milk quality.
• Learn more about Gram-negative mastitis at www.milkqualityfocus.com.