New York’s Quality Milk Production Services (QMPS), operated by Cornell University’s College of Veterinary Medicine Animal Health Diagnostic Center, provides producers with education and research on mastitis control. Four regional locations offer farmers field and laboratory culturing and diagnostic services. They serve all of New York and offer services in other states.

The QMPS offers guidance on how producers can best achieve and maintain quality milk. Their risk assessment “considers all of the important farm issues that influence udder health and milk quality on the farm,” Dr. Frank Welcome, senior extension associate at the QMPS Central Laboratory, said.

Welcome addressed videoconferencing participants during recent PRO-Dairy Milk Quality Management workshops. He discussed factors that influence mastitis risk and how best to alleviate those concerns.

Biosecurity concerns

“The classification system for contagious versus environmental mastitis is not as rigid as we once thought,” Welcome said. “Environmental can become contagious.”

Environmental mastitis encompasses infectious organisms not typically passed cow-to-cow during milking but present in the cows’ environment. Given the right environmental conditions, cows can become infected with these pathogens. Contagious mastitis, however, is readily transmitted from cow-to-cow during milking. In some cases, environmental strains can become contagious.

Prototheca, a mastitis-causing, colorless algae found widely in dairy cow environments, is an “emerging problem,” Welcome said. “Once it becomes established in a herd ... it does seem to be spreading quickly from cow to cow during milking.” It has caused increased culling and financial loss in New York and across the nation.

Biosecurity measures are most applicable in preventing cases of contagious mastitis. Before purchasing animals, screen the herd for pathogens, Welcome advised.

Even with pathogens that are intermittent shedders, such as Staphylococcus aureus, three bulk tank samples should show any positive results with approximately 95 percent certainty. With other organisms, there is a 90 percent chance of identifying an infection with one bulk tank sample.

“Infected cows are shedding billions of organisms into milk on a daily basis,” Welcome said.

Another biosecurity measure is to bring your own milking equipment to shows and fairs. Shared equipment is often responsible for transmitting infections between herds. Even in herds where the prevalence of mastitis is well controlled, a handful of cows typically remain infected.

Milking and mastitis

Milking procedures are very important for preventing and controlling contagious mastitis. Keeping the milking environment low-stress, reducing the milking time and using proper milking procedures are the basic steps needed to prevent contagious mastitis from gaining a foothold.

Lack of udder cleanliness is a primary risk factor in clinical mastitis. Thorough washing of the udder prior to milking is a requirement. Teat-end lesions and hyperkeratosis also put cows at risk for clinical mastitis.

Preventing teat chapping, which allows micro-organisms to embed into skin cracks, and routinely observing teats closely before milking can reduce the risk of mastitis infection. Using high-pressure hoses on the deck can aerosolize organisms in manure, and contaminated droplets can land on cows with teats open from milking. This is an often-overlooked route of mastitis infection.

Proper forestripping stimulates letdown and allows for examination of abnormal milk. Pre-dipping, done properly, includes dipping clean teats, dipping the entire length, allowing the treatment to remain on teats for 30 seconds and using proper drying techniques. Post-dipping teats is a crucial step for controlling the spread of contagious mastitis.

“You want to make sure that you’ve got an appropriate and approved teat dip that is applied properly,” Welcome said.

Milking cows in a logical order, from low-SCC groups to cows in treatment groups, is imperative. Maintain equipment regularly, guarding against pulsator or line issues that can increase the likelihood of contagious mastitis infection by impacting teat health. Improving milk harvest efficiency can reduce teat problems.

Decreasing herd risk factors

Cow nutrition is another key in mastitis prevention. Energy balance, particularly during the late dry and early lactation periods, is important in maintaining health. Trace minerals, such as selenium and vitamin E, also influence the immune system, along with copper and zinc. Feed palatability, bunk access and cow comfort can all impact dry matter intake (DMI).

“Review management procedures that may be affecting DMI,” Welcome said. “We want to have our nutritional needs met so animals are in a good, healthy situation.”

Dry cows and heifers are of primary importance in managing herd mastitis issues, Welcome said. Involuted udders signal a decreased mastitis risk, while the risk of infection increases dramatically if udders are up. Dry cows have a tendency to develop chronic infections, so preventing mastitis is critical for these animals.

“Even though cows are dry for a relatively short period of time, the risk of new infection during the dry period is between two and 12 times higher than during the entire lactation period,” Welcome cautioned. “You really need to manage the dry cows as well as, if not even better than, you do the lactating herd.”

Having uncrowded, low-stress conditions and a clean and dry environment reduces a farm’s mastitis risk. There should not be any standing liquid in alleyways. If cows are out on pasture, they need to be “on pasture, not mud.”

Accumulated manure in walkways also greatly increases risk as manure is splashed up onto udders. Hooves coated with manure quickly degrade bedding. Manure must be removed frequently, and bedding must be clean and adequate.

Other issues

Iodine, which is often used as a teat dip, is being increasingly scrutinized by the FDA, Welcome said, due to increased iodine levels found in the food supply. Peroxide is not adequate for dirty teats, which absolutely must be washed first prior to using a peroxide teat dip.

“The most appropriate (teat dip) product for a herd is going to depend on circumstances on that farm,” Welcome said.

Brush scrubbers have also been problematic because teats still need to be towel-dried to minimize mastitis infection risk. While brush scrubbers do stimulate teats very well, pathogens tend to survive on brushes and can contaminate the herd over time.

Herd performance indicators should be established for the farm and can then be utilized to “identify specific management issues that are affecting the farm’s SCC,” Welcome said. The dry cow cure rate is a useful indicator measurement. If there are high fresh rates of infection, environmental concerns and cow management issues need to be examined.

“It’s a very, very small number of cows that are responsible for most of the quality problems on the farm,” in most situations, Welcome said. “There are some mastitis vaccines that work very well,” but culling may be the only effective way to manage certain pathogens.

Welcome advised producers that pathogen-specific resource guides are available through the Animal Health Diagnostic Center’s New York State Cattle Health Assurance Program (NYSCHAP).

“If a farm finds that they’re dealing with a very specific mastitis pathogen, they can download the pathogen-based risk assessment guide.” PD

Tamara Scully, a freelance writer based in northwestern New Jersey, specializes in agricultural and food systems topics.

For additional resources for assessing your mastitis risk, visit the Quality Milk Production Services website.