Mastitis stands as one of the most financially burdensome diseases affecting dairy cows, with an estimated cost of $444 per case occurring within the first 30 days post-calving. The periods of highest risk are particularly noted at the beginning and end of the dry period, during which the absence of milk flow creates a conducive environment for bacteria to infiltrate the teat canal. As such, implementing effective prevention strategies is imperative, with proper dry cow nutrition playing a crucial role in mitigating the risk of mastitis.

Immune Challenges During Transition

The transition from a non-lactating to a lactating state poses significant metabolic and immune challenges for dairy cows. Research indicates that changes in immune function occur both before and after calving, thereby increasing susceptibility to various diseases. While inflammation serves as a normal immune response, excessive production of inflammatory mediators due to various stressors can lead to impaired immune function.

The immune system requires a substantial supply of nutrients, particularly glucose, amino acids, trace minerals such as copper, zinc, and selenium, along with vitamins A, D, and E. Fatty acids also play a role in modulating immune activity; for instance, ketone bodies resulting from ketosis have been shown to depress immune responsiveness. Current dairy nutrient guidelines may not adequately meet the nutritional needs of immune cells, suggesting that dietary modifications could enhance immune defense.

Nutritional Strategies to Reduce Mastitis Risk

• Vitamin E: Research conducted by Ohio State University demonstrated that increasing vitamin E intake beyond the National Research Council (NRC) recommendations significantly lowered mastitis incidence. The NRC’s 2001 update raised the suggestion for vitamin E intake during the dry period from 350 IU/day to 1,500 IU/day, with further studies indicating benefits at 4,000 IU/day. Cows exhibiting blood vitamin E levels below 3 µg/ml were found to have a nearly ninefold increased risk of mastitis, highlighting the necessity for supplementation, as traditional stored forages typically provide only around 1.5 µg/ml.
• Vitamin A: Studies from the University of Guelph established a correlation between elevated blood retinol levels and a 60% reduction in mastitis risk for every 100 ng/ml increase, although an optimal threshold was not specifically defined.
• Trace Minerals: Findings vary, but research from Penn State indicated that cows with elevated serum iron or reduced serum copper levels were at a heightened risk of mastitis. While iron supports bacterial growth, copper is essential for immune function and antioxidant activity. Care must be taken to ensure balanced supplementation, as excessive intake of any nutrient can be detrimental.

Implementing Effective Dry Cow Nutrition

The diet provided to dry cows is instrumental in preventing post-calving diseases, including mastitis. Many dry cow diets tend to minimize supplementation; however, the roles of vitamins and minerals cannot be overstated. Collaborating with a nutritionist is vital to ensure appropriate supplementation, while veterinarians can monitor and assess cow responses to dietary changes. Variability in nutrient intake, often influenced by factors such as overcrowding or heat stress, must also be taken into account, as intake differences in close-up pens can fluctuate between 5 to 8 lb/day.

Additionally, nutrient interactions can significantly impact availability. For example, vitamin A is prone to degradation in the rumen, especially when cows are fed high-starch diets. Therefore, precision feeding should prioritize achieving optimal nutrient levels in cows rather than merely formulating precise diets.

Conclusion

Optimizing dry cow nutrition serves as a proactive approach to preventing mastitis. Ensuring that cows receive adequate vitamin and mineral supplementation is essential for enhancing immune function and reducing the risk of infections. Collaboration between nutritionists and veterinarians is paramount in refining diets and monitoring cow health, ultimately leading to improved herd performance and productivity.

This article is based on research conducted by Robert J. Van Saun, DVM, MS, PhD, Extension Veterinarian.