A study by Oregon State University researcher Dr. Gerd Bobe found that metabolites in the blood are able to identify whether or not early milk-producing cows are prone to mastitis. The study was designed to identify predictive serum indicators of periparturient diseases in dairy cows. The findings, said Dr. Bobe, could be used to develop a simple early-detection tool that would enable dairy farmers to identify cows that benefit from preventative treatment.
Dairy cows are most susceptible to naturally occurring clinical mastitis in the first weeks after calving. Infection, however, may also occur during the close-up period or around calving when milk samples are not available. While traditional studies focus on indicators in milk samples at the onset of clinical mastitis, including somatic cell count, serum proteins, enzymes, electrolytes, degradation products of milk proteins, and acute phase proteins, Dr. Bobe chose to take a metabolomics approach, since milk samples were not available.
Dr. Bobe, who is an associate professor at Oregon State University, studied 160 pregnant cows several weeks before they gave birth, and compared those that
eventually developed mastitis to those that did not. After taking blood samples at different times during the close-up period and comparing cows that got mastitis to those that remained healthy, Dr. Bobe then compared lipids and metabolites of the cows doing a broad screen of different parameters.
While some researchers would choose to sample urine, Dr. Bobe chose to sample blood. “The problem sometimes with urine is there are a lot of metabolites, so there’s a lot of metabolism already going on,” he explained.
All of the animals received the same feed, eliminating potential results from dietary differences.
“After I measured the different parameters, I put them into different groups, similar pathways, and then looked to see if some pathways were more affected than others,” he explained.
The most mastitis-relevant parameter he saw was the presence of compounds that are built in the mammary glands, like lactose and 3’-sialyllactose. Typically, lactose and other carbohydrates that are associated with milk production will not appear in the bloodstream until a few days before calving. In the mastitis-infected cows, however, these metabolites were already present in their blood three weeks before calving. This indicates that they began producing milk early.
“Both were elevated in blood, so that means something that was built in the mammary gland actually had transferred back into the bloodstream,” he explained. “That I found very interesting. You wouldn’t expect things that were built in the epithelial cells to go back into the bloodstream.”
Searching for an explanation, Dr. Bobe read the work of other researchers and found that mastitis-infected cows have proteins that are usually in the blood transferring into the milk. “Mine was the first to show that the opposite was true,” he said.
“And then I found an article that said that when you don’t milk out cows, if you do it long enough, lactose will transfer back from the mammary gland into circulation,” he said. “And that is kind of a sign that they were not milked out properly because with the buildup comes inflammation and that destroys the barrier between the mammary gland and proteins can go to the other side.”
Inflammatory markers were included in the study; Dr. Bobe did notice an increase in affected cows. He believes that in some cases increased pressure on the mammary gland breaks the teat barrier. Environmental pathogens can then enter the mammary gland, causing infection.
“So what that basically says in my view is that the cows had a lot of milk in their mammary gland that was building up and leading to an inflammation,” he said.
While most producers won’t milk a pregnant cow, Dr. Bobe says if her teats start to leak, then the teat barrier is already broken. “You have to do something otherwise an infection comes in,” he said. “Once an infection comes in, since you’re not milking it out, it will make it worse.”
Milking earlier raises the question of lost colostrum. “This cow is most likely full in milk at that time,” he said. “This would be the colostrum, which I would use. Because it’s not like bloody colostrum when she has not fully built her mammary gland. This cow must have been making enough lactose that in my view she is most likely already full in milk. So you could still use that colostrum.”
“I’m just thinking about preventing infection because that’s what we want, in my view,” he continued.
“They have to be milked,” he added. “I don’t see any other option, unless you can keep them totally sterile, which I don’t think you can.”
Dr. Bobe’s research indicates that there could be what he calls a certain ‘metabotype’ or metabolic phenotype that could predict cows that are not as good at protecting themselves against specific diseases. He hopes that his findings will lead to the development of a simple test that could be used to help farmers identify mastitis-susceptible cows and those that would benefit from early, preventative treatment. He is uncertain, however, as to whether or not a test for 3’-sialyllactose could be developed.
By taking preventive steps before cows become infected, dairy producers can avoid treating udder infections with antibiotics. Reducing mastitis would also decrease the need to cull cows that suffer from chronic infections.