The most costly and most common disease in dairy cattle may soon have a new treatment option. A natural remedy — vitamin D — has been shown to delay and reduce the severity of mastitis infection in animals.

Mastitis, which affects the mammary gland or udder, costs the U.S. economy an estimated $2 billion per year. The disease can lead to a reduction in milk production, milk quality and income for dairy producers. In some cases, infected cows must be removed from herds.

Scientists at the ARS National Animal Disease Center (NADC) in Ames, Iowa, examined the role of vitamin D in altering the response of the cow's immune system to Streptococcus uberis, a mastitis pathogen.

"Research shows that specific levels of vitamin D need to be in the blood stream to prevent conditions like rickets, or softening of the bones," says molecular biologist John Lippolis, in the NADC Ruminant Diseases and Immunology Research Unit. "A higher level needs to be in the blood for proper immune function, but generally, milk has very little vitamin D until it is fortified during processing."

Lippolis and his colleagues at NADC used a form of vitamin D called pre-hormone 25 hydroxyvitamin D that's found in blood, but not in milk. Animals treated with vitamin D had a significant reduction in bacteria counts and less clinical signs of severe infection compared to untreated cows. In the early stage of the infection, as vitamin D reduced the bacterial counts, milk production was greater in the treated animals.

Scientists also looked at bovine serum albumin (BSA) in milk, as well as somatic cell counts—immune cells that enter the mammary gland to fight infection.

"BSA is a protein in blood that becomes a marker in milk to indicate when an infection gets really bad," Lippolis says. "The barrier between the milk and the blood can become a little bit degraded, indicating the severity of the disease."

Results showed that vitamin D affects the immune system and suggested that it could help reduce the need for antibiotics in treating mastitis. Lippolis says that vitamin D also has the potential to decrease other bacterial and viral diseases such as respiratory tract infections.

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