June 23, 2021

Identify organisms before treating mastitis

Dairy farm conditions that support bacterial growth

ITHACA, N.Y. — The majority of mastitis cases on dairy farms start when bacteria enters the teat end of a cow’s udder.

There are four things bacteria organisms need to survive, said Mike Zurakowski, DVM at Cornell University’s Quality Milk Production Services.

“All the conditions for bacteria to grow and thrive are in place in the udder and the environment where cows live,” said Zurakowski during a webinar organized by Hoard’s Dairyman.

Bacteria need nutrition, moisture, warmth and proper pH.

“Milk is a great nutrition source, moisture is in the udder, warmth comes from body temperature of the animal and most organisms survive at pH from 6.8 to 7.2,” Zurakowski said. “Once they get into the udder and they have all these needs met, they grow exponentially.”

Each dairy farm has its own types of organisms.

“On some farms we see higher levels of coliform bacteria such as E.coli and other farms have higher levels of Strep organisms, so every farm has its own breakdown of organisms,” Zurakowski said.

“My interest has always been to identify these organisms and once we know the organisms figure out the risk factor that is allowing the organisms to cause the cases of mastitis,” he said.

Dairymen can use a couple of methods to identify the organisms including taking a milk sample from the bulk tank or collecting individual cow samples.

“We also have on-farm PCR diagnostic systems, so we can look for bacteria based on their DNA,” Zurakowski said.

Mastitis can be caused by either contagious or environmental organisms.

“Once contagious organisms are in an animal they can be transmitted to another animal through the milking machine or your hands and often they are transmitted mostly during milking,” Zurakowski said.

“The most important thing is to identify which animals have the organisms, segregate the infected animals and milk them last or milk them with a separate unit,” he said. “Some of them we can treat with antimicrobials and for some the best scenario is to cull the animals.”

Environmental mastitis pathogens are organisms that come from the environment and are not generally transmitted from animal to animal.

“The organisms are usually picked up during milking if we don’t do a good job of prepping the teats or after milking when the animal is in the barn,” Zurakowski said.

“There are about 100 organisms that cause mastitis, but what we find on farms is usually a handful that are the most common,” he said.

Zurakowski recommends completing a milking system evaluation twice a year.

“On many farms dairymen maintain their milking system when it breaks,” he said. “We need to make sure our animals are happy when they are being milked, so go through your milking system on a routine basis.”

In addition, it is important to review milking procedures with people.

“Spend some time to make sure people are doing a good job with milking procedures and stall maintenance,” Zurakowski said.

Since the udder of a cow is never sterile, the goal is to try to reduce the bacterial load as much as possible during milking.

“I push for 80 to 90% of the herd with nice, clean udders,” Zurakowski said. “If you’re not at that level, stall maintenance is key.”

Dairyman can evaluate the bedding frequency and stall grooming to decrease the bacterial loads in the environment.

To determine the cleanliness of teat ends, the veterinarian uses gauze with a little alcohol to swab them.

“I want to see less than 10% with manure or debris,” he said. “To remove organisms from the teat ends both pre-dipping and pre-stripping are important, so we have well sanitized teats and good stimulation for milk let down.”

The pre-dip should have a minimum of 30 second contact time to destroy the bacteria.

“Allow 1.5 to 2.5 minutes for milk letdown and then attach the milker,” Zurakowski said.

“The cow only accounts for 20% of the contributions to mastitis. The other 80% are things we have power over like how the farm is managed, milking management and the milking machines,” he said. “When we have mastitis issues in the herd we have to look at ourselves first.”

The majority of mastitis cases, Zurakowski said, are mild or moderate.

“About 15% of the cases need to be jumped on right away with supportive therapy,” Zurakowski said.

“Studies compared blanket treatment where every case of clinical mastitis is treated versus selective treatment where they cultured the organism and only treated the ones that respond,” he said. “There was a 67% reduction in antimicrobial use or about $30,000 per 1,000 cows difference from cost of treatment, labor costs, culture costs and lost milk income.”