Researchers tested whether a special form of vitamin D could help dairy cows maintain healthy calcium levels around the time they give birth. Forty-two cows received either regular vitamin D or a more active form called 25-OH-D3. The cows getting the special vitamin D form had better calcium levels on their calving day, fewer cases of udder infections, and lower stress markers in their blood. This suggests that this particular vitamin D form may help protect dairy cows during the challenging transition period around birth.

The Quick Take

  • What they studied: Whether a special form of vitamin D (called 25-OH-D3) works better than regular vitamin D to keep calcium levels healthy in dairy cows around the time they give birth.
  • Who participated: 42 adult female Holstein dairy cows that had given birth before. The cows were divided into two groups: one receiving regular vitamin D and one receiving the special form of vitamin D.
  • Key finding: Cows receiving the special vitamin D form had significantly higher calcium levels in their blood on the day they gave birth (1.08 compared to 0.99 units), and they had fewer udder infections and lower stress markers in their blood after birth.
  • What it means for you: If you work with dairy cows or own a dairy farm, using this special vitamin D form during the weeks before and after calving may help keep cows healthier and reduce costly infections. However, this is one study in cows, so more research would help confirm these benefits.

The Research Details

This was a controlled experiment where researchers divided 42 dairy cows into two groups. One group received regular vitamin D supplements (called cholecalciferol or D3), while the other group received a more active form of vitamin D (called 25-OH-D3 or HyD). The special vitamin D form is already partially processed by the body, so it may work faster than regular vitamin D, which needs to be processed by the liver and kidneys first.

The cows were fed these supplements for three weeks before their expected birth date and for three weeks after giving birth. Researchers collected blood samples multiple times during this period to measure calcium levels, vitamin D levels, and other important markers of cow health. They also tracked how much the cows ate, how much milk they produced, and whether they developed any health problems.

Both groups of cows ate the same basic diet (a total mixed ration), so the only difference between them was the type of vitamin D supplement they received. This design helps researchers determine whether the vitamin D form itself made a difference, rather than other factors.

The period around when dairy cows give birth is extremely stressful on their bodies. Their calcium levels often drop dangerously low (a condition called hypocalcemia), which can lead to serious health problems like milk fever, weak muscles, and infections. By testing whether a more active form of vitamin D helps maintain calcium levels, researchers can potentially find ways to prevent these costly health problems. This matters because sick cows produce less milk, require expensive veterinary care, and may need to be removed from the herd.

This study was published in the Journal of Dairy Science, a respected scientific journal. The researchers used a randomized design, meaning cows were randomly assigned to each group, which helps reduce bias. They measured multiple important health markers and collected blood samples at specific times to track changes. However, the study included only 42 cows, which is a relatively small number, so the results may not apply to all dairy farms or all types of cows. The study was conducted in a controlled research setting, which may differ from typical farm conditions.

What the Results Show

The main finding was that cows receiving the special vitamin D form (25-OH-D3) had significantly higher calcium levels in their blood on the day they gave birth compared to cows receiving regular vitamin D. Specifically, the special form group had calcium levels of 1.08 units compared to 0.99 units in the regular vitamin D group. This difference is important because calcium is critical for muscle function, nerve signaling, and milk production right after birth.

Interestingly, the special vitamin D form achieved this benefit by increasing the amount of the vitamin D form itself in the blood, but it did not increase the amount of the most active form of vitamin D (called 1,25-dihydroxyvitamin D3). This suggests that the special form works through a different pathway than previously thought.

Cows receiving the special vitamin D form also showed lower levels of a stress marker called BHB (beta-hydroxybutyrate) in their blood after birth. BHB increases when cows are under metabolic stress, so lower levels suggest these cows were handling the stress of birth and early milk production better.

Additionally, there was a trend toward fewer cases of mastitis (udder infection) in the special vitamin D group compared to the regular vitamin D group, though this difference was not quite statistically significant.

The amount of food the cows ate changed slightly between groups around the time of birth. Cows in the special vitamin D group ate slightly less food for a few days before birth but ate slightly more food for a few days after birth. However, this difference was small and did not affect how much milk the cows produced or their body weight. Milk production, milk quality (protein and lactose content), and body condition score were the same in both groups, suggesting that the vitamin D form did not negatively affect overall productivity.

Previous research has shown that low calcium levels around birth are a major problem in dairy cows and can lead to serious diseases. Some earlier studies suggested that vitamin D supplementation might help, but results have been mixed. This study adds to that research by showing that a more active form of vitamin D (25-OH-D3) may work better than regular vitamin D for maintaining calcium levels specifically on the day of birth. The finding that this form works without increasing the most active form of vitamin D is new and suggests scientists may need to reconsider how vitamin D works in transition cows.

This study had several limitations that readers should understand. First, only 42 cows were studied, which is a relatively small number. Results from small studies can sometimes change when larger studies are conducted. Second, the study was conducted at a research facility with controlled conditions, which may not reflect how cows are managed on typical farms. Third, the study only tracked cows for about three weeks after birth, so we don’t know if the benefits continue longer. Fourth, the difference in mastitis cases was not quite statistically significant, meaning it could have happened by chance. Finally, the study was conducted in one breed of cow (Holstein), so results may not apply to other dairy cow breeds.

The Bottom Line

Based on this research, dairy farmers and veterinarians may consider using the special vitamin D form (25-OH-D3) during the transition period (three weeks before to three weeks after birth) as a way to help maintain healthy calcium levels and potentially reduce udder infections. However, this recommendation comes with moderate confidence because it is based on one study with a relatively small number of cows. Farmers should discuss this option with their veterinarian to determine if it makes sense for their specific operation. The special form appears safe and did not negatively affect milk production or cow health in this study.

This research is most relevant to dairy farmers, veterinarians, and farm managers who work with high-producing dairy cows. It may be especially important for farms that have experienced problems with low calcium levels or udder infections around the time cows give birth. Cow owners should not attempt to give cows vitamin D supplements without veterinary guidance, as improper dosing could cause problems. This research is less relevant to people who consume dairy products, though they may benefit indirectly if it helps keep dairy cows healthier.

The benefits of the special vitamin D form appeared quickly—researchers saw differences in blood calcium levels on the day the cows gave birth. The reduction in stress markers and potential reduction in udder infections would likely be seen within the first few weeks after birth. However, farmers would need to start supplementing several weeks before the expected birth date to see these benefits, so planning ahead is important.

Want to Apply This Research?

  • If using this vitamin D supplementation protocol, track blood calcium levels on the day of calving and monitor the incidence of mastitis (udder infections) in the weeks following birth. Users could record: (1) blood calcium measurements on calving day, (2) number of cows developing mastitis in the first 21 days after birth, and (3) milk production in the first week postpartum to ensure productivity is maintained.
  • Dairy farm managers could implement a protocol to provide the special vitamin D form (25-OH-D3) to transition cows starting 21 days before expected calving through 21 days after birth. This would involve: (1) identifying expected calving dates, (2) ensuring the supplement is available and properly dosed, (3) recording which cows received the supplement, and (4) monitoring health outcomes.
  • Establish a long-term tracking system that records: (1) which cows received the special vitamin D supplementation, (2) their blood calcium levels around calving, (3) health problems in the first month after birth (especially mastitis), (4) milk production in early lactation, and (5) overall herd health outcomes. Compare these metrics between cows that received the supplement and those that did not to determine if the investment is worthwhile for your specific operation.

This research describes the effects of vitamin D supplementation in dairy cows under controlled research conditions. These findings should not be applied to individual cows without consulting a veterinarian. Vitamin D supplementation must be properly dosed, as excessive amounts can be harmful to animals. Farm managers should work with their veterinarian and nutritionist to determine if this supplementation strategy is appropriate for their specific herd, considering factors such as current feed composition, water mineral content, and individual cow health status. This study represents one research trial and should be considered alongside other available evidence and professional guidance. Results may not apply to all dairy operations, cow breeds, or management systems.