Udder Health: Closing the Barn Doors On Mastitis

When Bovine Health Watch talked with Greg Goodell, DVM, of The Dairy Authority in Greeley, Colo., about udder health, it didn’t take long for the conversation to turn to mastitis.

And that’s no surprise when you consider the impact of this serious problem.

Goodell says mastitis is the most expensive disease in the dairy industry, one that can affect milk production long after the infection has been cured. According to researchers at Virginia Tech, it costs U.S. producers more than $17 billion each year in lost production, discarded milk, increased labor and medical bills. That translates into 11 percent of our nation’s total milk production.

Mastitis, defined as inflammation of the mammary gland or udder, occurs in response to damage to these tissues. Most commonly, the damage is caused by bacteria, but it can also be due to physical injury and the effects of chemicals or other toxins.

Goodell says the most common bacterial culprits are coliform bacteria (E. coli, Klebsiella spp, etc.), Staphylococcus (Staph) species (Including S. aureus), Streptococcus (strep) species and Mycoplasma. Such pathogens—and the mastitis they cause—are classified as “contagious” or “environmental.” The contagious form is spread from cow to cow, usually due to unsanitary milking practices in the parlor. Environmental mastitis occurs when the cow’s environment outside the milking parlor creates opportunities for bacteria to spread.

Minimizing environmental pathogens. “Coliforms, such as E. coli cause the most severe cases of mastitis,” explained Goodell, a partner in The Dairy Authority, a veterinary practice that specializes in dairy cows and operates a lab that provides extensive milk quality testing for a variety of bacteria. “Clinically, cows can develop a substantial coliform infection within 8-12 hours of exposure,” he explained.

“Coliform agents are transmitted through manure contaminating the environment,” Goodell added, “So, anything you can do to minimize exposure to manure is helpful.”

He suggests increased maintenance, including harrowing to encourage manure to dry out in corrals. For free-stall situations, clean bedding and manure removal are musts. He also says it’s important to avoid overcrowding in either corrals or freestall barns.

“Too many cows in a corral won’t allow the lot to dry out; harrowing will just move the manure around. You have to dry manure out so that it turns into something similar to compost.”

Another way to reduce the incidence of environmental mastitis infection, according to Goodell, is to keep cows standing for 15-20 minutes after milking to allow their teats to close and seal out bacteria. Making sure that fresh feed is present—either by feeding at milking time or just pushing the feed up to the bunk so freshened feed is presented— encourages cows to eat, rather than lie down, after milking.

Goodell said that core antigen vaccines can also be used to reduce the incidence of severe cases of E. coli infections. He said studies show that the severity of E. coli mastitis is decreased significantly when cows are vaccinated with a core antigen vaccine. In some dairies the rate of severe infections is reduced from 20-30 percent down to less than 5 percent.

Reducing contagious causes in the parlor.

Most contagious types of mastitis are spread by improper sanitation or milking procedures in the parlor.

On the sanitation side, Goodell emphasized that strict procedures must be adhered to when milking in order to prevent the spread of contagious organisms such as Staphylococcus aureus (Staph aureus), Streptococcus agalactiae (Strep ag) and Mycoplasma. He recommends the following protocol:

• Prep the cow by pre-dipping with a sanitizer such as iodine, then wiping the teats with a towel;
• Use one towel per cow; never use the same towel on multiple animals;
• Express (“strip”) a small amount of milk from each quarter onto a surface (stripcup, parlor floor, etc.) that allows for easy observation of clinical signs of mastitis (clots, flakes, blood or abnormal color);
• After milking, dip or spray teats with a post dip to kill any organisms the cow may come in contact with after milking.

Mechanical issues in the parlor may cause mastitis as well and spread contagious or environmental organisms in the parlor.

“A milking machine that is left on too long, or set at a vacuum level that’s not correct for the equipment being used (too high or too low) can cause not only poor milk-out, but trauma to the teat itself by impeding blood flow in the teat,” Goodell said. “This leaves the tissue weakened or damaged and allows pathogens to invade easier.”

He added that “vacuum pressure set too low for the equipment being used, or anything that causes liner slips of the milking unit itself, can cause bacteria to be injected up into the teat during the milking process.”

Detecting subclinical mastitis.

While cows with full-blown mastitis show abnormal milk and swelling, subclinical mastitis displays no visible signs. Consequently, many producers test every cow for somatic cell counts (SCC) on a monthly or quarterly basis.

“If the SCC of the individual cow is 200,000 or less, we deem that cow healthy,” said Goodell. “If the count is more than 200,000 there is a good chance that the cow is experiencing a subclincal infection.”

Many producers rely on bulk tank SCC for their entire herd, rather than testing cows individually on a regular basis. Then, if a tank SCC is high, they test individual cows to identify infected animals.

A protocol that Goodell’s practice recommends frequently for clients is to culture fresh cows and all cases of clinical mastitis. The culture identifies any subclinical infections present and provides the basis for appropriate medication and treatment. It also allows for selective therapy to cows with different infections so the bacteria causing the mastitis can be treated successfully the first time.

A protocol that Goodell’s practice recommends frequently for clients is to culture fresh cows and all cases of clinical mastitis. The culture identifies any subclinical infections present and provides the basis for appropriate medication and treatment. It also allows for selective therapy to cows with different infections so the bacteria causing the mastitis can be treated successfully the first time.

“While it is important to have an established mastitis monitoring program with regular sampling as part of your routine, producers don’t have to worry about delivering samples to the lab every single day.” Goodell elaborated. “In fact we have very successfully created ‘treatment by culture programs’ where producers submit milk samples to the lab once or twice a week. This allows an organized and methodical approach for implementing a protocol on the dairy for all cows. Such a protocol detects contagious organisms and subclinical mastitis in fresh cows and identifies the causative agent for cases of clinical mastitis in a standardized fashion.”

Mycoplasma, Staph aureus and Strep ag are very contagious, so it’s important to identify them in fresh cows and clinical cases and take appropriate management steps, such as segregating/milking last, treatment, or culling,” he explained. “Strep ag can often be treated successfully with antibiotics; however, it is still cheaper to detect it before it spreads throughout the herd. For Mycoplasma there’s no effective treatment, so if it is not found early on in the individual cow, the whole herd can be affected in a very short time.”

Unfortunately, it’s currently impossible to eliminate mastitis entirely from your dairy operation. However, by employing sound environmental and parlor management practices, coupled with effective testing, you can reduce its prevalence—and severity—considerably. That means better herd health and increased profits, both now and in the future.

Common Bacterial Causes of Mastitis

Environmental Pathogens:

Coliform agents, including E. coli and Klebsiella spp
Minimize by reducing exposure to manure
Core antigen vaccines can reduce incidence of severe cases

Contagious Pathogens:

Staphylococcus (Staph) specicies, including S. aureu and, S. agalactiae
Streptococcus (strep) species
Mycoplasma

Reduce infection through sound sanitary parlor practices, including pre dip, expressing, and post dip