A previous edition of Country Folks provided information from a seminar given by Dr. Ernest Hovingh at the Penn State Mastitis and Milk Quality Conference on the importance of recognizing the different pathogens that cause mastitis in dairy cows so the appropriate treatment can be implemented. A continuation of that list and insight on how to prevent mastitis can be found below.
Yeasts and Molds
Then there is the big list of yeasts and molds. Although it is rare, you can see outbreaks of these in mastitis cases. They often typically present like coliforms or hot mastitis. The cases can look very similar to those caused by coliforms. Nocardia and yeasts can survive 3 to 4 months or more in the udder, and can cause fibrosis of the gland and reduced milk production.
Treating with an antibiotic doesn’t make sense, because these organisms aren’t going to respond to approved products. If you culture and find them, don’t treat. Sometimes, after a period of time, these pathogens may just clear. “We don’t know why some do and some don’t,” said Hovingh. “But if you’re patient, some cases may disappear.”
Although they are environmental pathogens, they may occasionally be spread by multiple-use infusion bottles, or contaminated infusion tips. Very rarely, these pathogens may be found contaminating individual infusion syringes.
“Sometimes it’s pretty scary what people are putting in the udder in an attempt to treat yeasts — and it may be illegal,” cautioned Hovingh, “but it’s generally unrewarding to treat them, especially Nocardia. Although they may clear on their own, it may take months.”
This pathogen can’t be cultured in the normal culture set-up. M. bovis is, thankfully, rare in most herds. It’s often a large herd issue, where cows are comingled from several herds. In some herds, however, it can be a fairly common infection.
But after a fairly severe mastitis outbreak, the disease generally settles down to a rather low-grade, chronic infection in the herd, in a relatively few individuals. Most of the transmission occurs at milking time. The ‘classic’ signs of M. bovis include sandy-looking, yellowish milk. This pathogen is one of the things to consider if you have an acute outbreak of mastitis in the herd, especially if you’ve recently purchased cows. You may also see calves with head tilts if you are feeding them unpasteurized waste milk with mycoplasma in it.
There are several ways you can approach M. bovis infection in your herd. Keep in mind that you could have chronic carriers with periodic flare-ups. “Some people just try to live with it, and some people try to eradicate it,” reported Hovingh, who said he is not sure that one approach is necessarily better than the other.
“Treatment is often unrewarding, and eradication can mean an awful lot of cultures, a separate “myco pen” for infected cows, and often you have to get rid of a lot of cows in the end. I’m not sure if that’s economical,” he added. On a positive note, sometimes M. bovis does clear from individual cows on its own.
For disease prevention, we’re talking about special care in housing and feeding areas — but especially at milking time. Practice good udder hygiene. If teats are covered with dirt, there’s a pretty high level of exposure, even if they’re cleaned well for milking. Most important for contagious bacteria control is applying an effective post-milking teat dip to the complete surface of every teat of every cow immediately after milking.
The pathogens that usually cause clinical disease — abnormal milk and occasionally sick cows — include the coliforms, mycoplasmas, yeasts, and often the environmental streps. Try to minimize environmental exposure to these pathogens — udder hygiene is extremely important! Genetics and conformations that confer higher susceptibility do exist. Nutrition can affect the strength of the immune system. Be sure to give your cows clean places to lie down and walk through. If you go over 100 percent stocking density, be aware this carries a higher measure of risk and requires very careful management.
“Don’t make too many assumptions,” cautioned Hovingh, “and be sure you check them once in a while. In the end, you can’t really be sure what is causing mastitis in your cows if you don’t check!”