Causes of Milk Fever
After calving, a cow’s calcium demand surges due to milk production, increasing two to three times compared to the dry period. Since dietary intake alone isn’t enough, calcium must be mobilized from bones or absorbed from the intestine. This process needs to be “primed” before calving to ensure a quick response.
Blood calcium levels typically drop after calving but should recover by day three or four. If not, the cow faces higher risks of transition-related health issues.
Identifying At-Risk Cows
Clinical milk fever is easy to spot—affected cows are weak, unsteady, and unable to stand due to low calcium. Subclinical cases, however, show no visible signs but have low blood calcium levels when tested.
Currently, there are no on-farm tests for fresh cow calcium levels. Blood samples taken 2–4 days post-calving can help identify herd issues, with fewer than 25% of fresh cows ideally having calcium levels below 8.6 mg/dL.
Why Prevention Matters
Cows with milk fever or subclinical hypocalcemia are more prone to displaced abomasum, ketosis, metritis, and retained placenta. They are also less likely to show estrus by 60 days in milk (DIM) and have a higher risk of early culling.
Prevention Strategies
Dietary Management: Feeding close-up dry cows (within three weeks of calving) a low-potassium diet, such as corn silage-based rations with anionic salts, reduces hypocalcemia risk. Urine pH should be monitored, with an optimal range of 5.5–7.0. Mildly acidifying diets can help but are less effective than fully acidified DCAD diets.
Calcium Supplementation: Routine oral calcium boluses are not recommended for all cows, as effects are temporary. However, older, lame, or high-producing cows may benefit, while first-lactation and lower-producing cows might not. More research is needed to refine supplementation strategies.
Conclusion
Proper transition cow management minimizes milk fever risks, improving health, reproduction, and herd longevity. Implementing targeted dietary strategies and monitoring calcium levels can enhance productivity and reduce early culling.
