Mastitis in Dairy Cows.

 By Heather Smith Thomas.

 Mastitis simply means inflammation and/or infection in one or more quarters of the udder.  Signs of mastitis often include swelling, heat, redness and pain in the udder.  Acute mastitis can cause fever, depression, loss of appetite and weight, septicemia, and death.  Mastitis can also become chronic if the inflammatory response persists over a long period of time.

Dr. Jennifer Pearson, Assistant Professor, Bovine Health Management, University of Calgary Faculty of Veterinary Medicine says mastitis is much more common and researched more, in dairy cattle than beef cows, due to the importance of quality milk production in the dairy industry.

Risk factors for mastitis include older cows with abnormal teat conformation and low-hanging udders, but younger cows in contaminated environments or in overcrowded areas can also get mastitis. “Cows with mastitis may have blood or clots in the milk.  In the worst cases, the quarter may be cold, blue, and the cow might be off feed and dehydrated from septic shock.

Early detection and treatment of mastitis is critical for the cow,” Pearson said.Large pendulous udders that have lost their suspensory support are more likely to be exposed to bacterial infection.  Large teats, and teats that are deformed or damaged at the tip may let in bacteria.

Mastitis can develop in response to tissue damage to the teat and/or udder.  Abrasions, lacerations or bruising, weather wind burn or frost damage increase the risk.  Large bottle-shaped teats and pendulous udders that hang below the hocks are exposed to injury.  A pendulous udder that swings back and forth as the cow travels may get bumped by her hocks.  Mastitis may occur if the udder is bruised; damaged tissue creates ideal conditions for some types of infection to get started.  

Dr. Shelie Laflin, a Kansas veterinarian, says dairy cows are most at risk because of the larger mammary gland and udders that are frequently handled.  “Automatic milkers cause the teat orifice to open, and the teats are handled by humans,” she says.

If the teat orifice is not tightly closed (as when the large quarter is leaking milk), it may be at risk for bacteria to enter.  “If another cow steps on her teat or it gets snagged in the brush or on a fence, the teat end may be damaged so it can’t close properly, and pathogens enter,” said Laflin.

If a quarter becomes contaminated and infection stays localized, the mammary tissue in that quarter may be destroyed but the infection is usually not life-threatening.  If the quarter is permanently damaged it will dry up, and be small and dry the next time she calves.  If infection gets into the bloodstream, however, the cow may become sick.   Unless treatment is swift and diligent, you may not only lose the quarter or part of the udder; you may also lose the cow.

Joe Armstrong, DVM (Cattle Production Systems, Extension Educator, University of Minnesota) says there are usually two causes of mastitis—environmental causes and contagious causes.  “Environmental pathogens would include something like E. coli,” he explains.  E. coli bacteria are often present in feces and may contaminate bedding and the environment where the cows spend time.  

“The most dangerous time for the cow to pick up bacteria is post-milking, while the teat end is still open.  It takes about a half hour for that to close.”  Pathogens from the environment could enter the teat during that time.

Then there are the contagious pathogens that can be transferred from cow to cow.  “There are many different ‘bugs’ that can do that.  They can be transferred in bedding and at milking time.  Often they can be transferred via people during the milking process.”

Occasionally, mastitis is just one of the side effects of a bigger problem.  “There are some disease processes that can predispose cows to mastitis, or poor transition management or a prolonged negative energy balance.  Mastitis is often a systems problem.  There can be many factors involved, and more than one root cause, including stress,” he explains.  It’s important to look at the big picture.

In terms of prevention, on the environmental side the important thing is general cleanliness.  “This includes proper preparation for milking, and all the things that go into it.  Thus it is important to keep everything clean and dry, and keep the cows comfortable, since cow comfort plays into susceptibility to mastitis, as well,” says Armstrong.

“On the contagious side, we need to control the pathogens within a herd, and identify any cows that cannot be treated and get rid of them.  Otherwise, treatment is necessary, and culturing is a big piece of that so that you can identify what you are dealing with, and which cows need to go and which ones can be treated,” he says.

Regarding treatment, it is important to work closely with your herd health veterinarian, since some types of mastitis are more serious and it is crucial to know what you are dealing with.  “Sometimes this can be determined just by observing clinical signs, but often we need a culture to tell us what’s going on.”

Clinical signs may be physical changes in the udder or the milk, and a systemic infection will be indicated if the cow goes off feed or has a fever.  “Systemic infections can be quite serious, especially with some of the environmental pathogens such as E. coli or Klebsiella.  Those can create some very toxic results--sometimes bad enough that the cow will die,” says Armstrong.  Even if the cow survives, she may lose a quarter or even the entire udder.

In these situations the pathogens are generally gram-negative and we can’t adequately combat the pathogen itself.  “The main thing is to provide good supportive care to help the cow get through it and help her calm down her own inflammation, since this is usually the bigger problem,” he says.

Treatment
Intra-mammary treatments for dairy cows (infusing an antibiotic preparation directly into the teat canal) are a standard procedure for cows with mastitis.  “This requires multiple treatments, usually at each milking,” said Laflin.  “This is still the treatment of choice, along with keeping that quarter empty, milking it out at least twice a day and then infusing the medication.”

Pearson also recommends frequent milking, anti-inflammatory medications to treat pain and inflammation (Banamine or Meloxicam), and an antibiotic given either systemically or in the affected quarter.  “Working with your veterinarian is critical to select an appropriate antibiotic for bacterial infection, and to develop an appropriate treatment protocol,” Pearson said.

Some infections are much more serious.  “Certain pathogens like Archanobacter pyogenes cause an abscessing type of mastitis, and often the best strategy is to destroy that quarter and let it drain so it can heal,” Laflin said.  The cow loses that quarter’s production, but you save the udder, and the other quarters tend to compensate by producing more milk.  Most dairymen choose to cull a cow, however, that loses a quarter.

“Systemic treatment (such as intramuscular injection) isn’t needed unless a cow is systemically ill. Environmental pathogens like E. coli, or Klebsiella can make the cow very sick.  Then you must treat immediately with the appropriate antibiotics.  These can be aggressive pathogens, killing a cow in a matter of about 12 hours,” said Laflin.  

Mastitis is a huge topic.  “We have done four podcasts on this, that are each about 30 minutes long, to cover the basics of mastitis,” says Armstrong.  Anyone who wants to get more details can access these podcasts by going to The Moos Room Podcast - z.umn.edu/themoosroom and look for Episodes 29, 30, 59, 60 which are related to mastitis.

“It takes a long time to go through the basics of this disease complex and there is so much to talk about.  It’s hard to cover all of these in an article, so we recommend that people listen to the podcasts,” he says.