Dairy cows often struggle with calcium levels right before and after giving birth, which can cause serious health problems. Researchers tested whether feeding pregnant cows different types of diets could help their bodies manage calcium better. They found that cows fed a special acidifying diet (made with corn silage and containing certain minerals) had better calcium levels after birth compared to cows on a standard diet. This research suggests that what farmers feed cows in the weeks before calving can significantly impact the cow’s ability to maintain healthy calcium levels during this critical time.

The Quick Take

  • What they studied: Whether different types of feed given to pregnant dairy cows in the three weeks before birth could improve how their bodies handle calcium
  • Who participated: 28 healthy Holstein dairy cows (a common dairy breed) during their final three weeks of pregnancy and first few days after giving birth
  • Key finding: Cows fed a special acidifying diet (containing corn silage and specific mineral additives) had better active calcium levels in their blood after birth compared to cows on a regular diet, suggesting this feeding strategy helps calcium absorption
  • What it means for you: If you work with dairy cows, adjusting their diet before birth may help prevent calcium-related health problems after calving. However, this is one study on a relatively small number of cows, so more research is needed before making major farm changes

The Research Details

Researchers divided 28 pregnant Holstein cows into four groups. All cows started on a standard diet made of grass silage and barley straw. Three weeks before expected birth, the cows were randomly assigned to different diets: one group continued the standard diet, while three other groups received special high-energy diets designed to create mild acidity in the cow’s body (using corn silage and added minerals like magnesium chloride). The researchers collected urine samples weekly and blood samples from an artery in the cow’s ear at specific times: 12 days before birth, and at 0.5, 1.5, and 2.5 days after birth.

The key difference between the diets was their ‘dietary cation-anion difference’ (DCAD), which is a measure of acidity and alkalinity in the feed. The standard diet was alkaline (DCAD +300), while the special diets were acidifying (DCAD -70 to -100). One group received a gradual transition diet for 7 days before switching to the most acidifying diet for 14 days.

This design allowed researchers to compare how different feeding strategies affected the cow’s calcium metabolism during the critical transition period around birth.

The weeks right before and after a cow gives birth are extremely stressful for her body. During this time, calcium levels often drop dangerously, which can cause serious conditions like milk fever that can paralyze the cow or even be fatal. Understanding how to keep calcium levels stable through diet could prevent these life-threatening problems and improve cow health and milk production

This study was a randomized controlled trial, which is a strong research design. However, the sample size was relatively small (28 cows total, with some groups having only 6-8 cows), which means results should be interpreted cautiously. The researchers used objective measurements (blood and urine samples) rather than relying on observation alone. The study was published in a peer-reviewed scientific journal, meaning other experts reviewed it before publication. One limitation is that the study only looked at one breed of cow (Holstein), so results may not apply to other dairy breeds

What the Results Show

Cows fed the acidifying diets showed lower urine pH (more acidic urine) seven days before birth, confirming that the special diets were creating the intended mild acidosis in their bodies. Cows on the most acidifying diet (MGC-100) and the gradual transition diet (OVE) had lower blood pH 12 days before birth compared to the standard diet group.

After birth, the results were striking: cows fed the acidifying diets had higher levels of active calcium (ionized calcium) in their blood compared to cows on the standard diet. This difference appeared as early as 0.5 days after birth in the most acidifying diet group and by 2.5 days after birth in the other acidifying diet groups.

Interestingly, cows on the acidifying diets actually had higher blood pH (less acidic blood) after birth, even though they had lower pH before birth. This suggests their bodies adapted to the dietary changes. By 2.5 days after birth, cows on acidifying diets also had higher total calcium levels in their blood.

The study revealed an important distinction: measuring ‘active calcium’ (ionized calcium) gave different results than measuring ’total calcium’ at certain time points. Active calcium is the form that actually works in the cow’s body, while total calcium includes both active and inactive forms. This finding suggests that farmers and veterinarians should pay attention to which type of calcium measurement they’re using, as they can tell different stories about a cow’s calcium status

Previous research has suggested that feeding acidifying diets before birth might help cows absorb calcium better, but most studies measured only total calcium. This study is notable because it measured active calcium, which is more directly related to how well a cow’s body can actually use calcium. The findings support the theory that acidifying diets help calcium metabolism, and they add new evidence by showing improvements in the form of calcium that matters most for the cow’s body

The study included only 28 cows, which is a relatively small number for drawing broad conclusions. All cows were the same breed (Holstein), so results may not apply to other dairy breeds. The study lasted only a few days after birth, so we don’t know if the benefits continue longer or translate to better health outcomes. The research was conducted in what appears to be a controlled research setting, which may differ from typical farm conditions. Additionally, the study didn’t measure whether these calcium improvements actually prevented milk fever or other health problems

The Bottom Line

Based on this research, feeding dairy cows a special acidifying diet in the three weeks before birth may help improve their calcium status after calving. However, this recommendation comes with moderate confidence because the study was small and only measured calcium levels, not actual health outcomes. Farmers interested in trying this approach should consult with their veterinarian and nutritionist, as these diets require careful formulation and monitoring. The gradual transition approach (starting with a milder diet then moving to a stronger one) may be worth considering as it appeared effective in this study

This research is most relevant to dairy farmers and veterinarians who manage Holstein cattle or similar dairy breeds. It’s particularly important for operations that have experienced problems with milk fever or other calcium-related issues after calving. Farmers with smaller herds or those using pasture-based systems may find it harder to implement these feeding strategies. This research is less relevant to beef cattle operations or non-dairy animals

Based on this study, improvements in calcium levels appeared within 0.5 to 2.5 days after birth. However, the study didn’t track longer-term outcomes, so we don’t know how long these benefits last or when they might translate to visible health improvements. Farmers should expect to see changes in blood calcium levels quickly, but preventing actual health problems like milk fever would require longer-term observation

Want to Apply This Research?

  • Track the timing and composition of pre-calving diets for each cow, then record blood calcium levels (if available through veterinary testing) at 0-3 days after birth. Compare these measurements across different feeding strategies to identify which approach works best for your herd
  • If using a dairy management app, create a reminder system to switch pregnant cows to their pre-calving diet exactly 21 days before expected birth. Log which diet protocol each cow receives and set alerts for blood testing around birth to monitor calcium status
  • Establish a baseline by testing calcium levels in cows on your current feeding program. Then gradually transition to an acidifying diet protocol for new groups of pregnant cows, testing their calcium levels at similar timepoints (12 days before birth and 0.5-2.5 days after birth). Track health outcomes like milk fever incidence, milk production, and reproductive performance over several months to determine if the dietary change provides real benefits on your farm

This research describes findings from a single study on 28 cows and should not be considered definitive medical or nutritional advice for your herd. Calcium management in dairy cows is complex and varies based on many factors including breed, age, milk production level, and overall farm management. Before making significant changes to your feeding program, consult with a veterinarian and a ruminant nutritionist who can evaluate your specific situation. This research measured calcium levels but did not directly measure whether these dietary changes prevented disease or improved health outcomes. Always work with qualified professionals before implementing new feeding strategies on your farm