Sunshine Vitamin Boosts Dairy Cows' Immunity

A new study shows how vitamin D can help dairy cows fend off infections, offering opportunities for better animal health and welfare improvements in the agricultural industry.

Vitamin D is a fat-soluble vitamin that is important for proper calcium absorption in the body. Cows (like humans) produce the vitamin in their skin when exposed to sunlight. It can also be absorbed when part of their diet.

Previous studies have associated vitamin D deficiency with increased incidences of infection and reproductive disorders in dairy cows. University of Florida researchers studied how vitamin D status could help protect pregnant dairy cows from infections, as during this time, cows are most vulnerable to disease.

The dairy industry in the U.S. is a $31 billion a year business, responsible for about 20 percent of the nation's farm income. A substantial percentage of that money goes toward the purchase and care of dairy cows. A single cow can be worth as much as $20,000, so optimizing health is essential to all involved in the industry - from farmers to veterinarians to those food manufacturers.

This study examined how increasing doses of two different forms of vitamin D—cholecalciferol and calcidiol—influenced immune biomarkers in pregnant cows. The two forms of vitamin D are known to have distinct effects on the immune system.

The scientists took blood samples to measure levels of vitamin D metabolites and inflammatory markers. They also isolated genetic material from white blood cells to look for changes in the expression of immunity-related genes.

Cows that consumed the calcidiol form of vitamin D showed clear gene expression signatures associated with enhancements in the innate immune system. These included an uptick in the expression of genes involved in cell adhesion and migration, cell-to-cell communication, and pathogen killing.

"The changes observed in this experiment suggest that providing vitamin D beyond the amounts needed to prevent perceived deficiency, in particular by supplementation with calcidiol, might play a role in supporting innate immune defenses in dairy cows," said senior author José Eduardo P. Santos. The results were published in the Journal of Dairy Science.