On April 20 here in the Madison area, the temperature soared above 70 degrees for the first time in 190 days. This was certainly a welcome relief and we are hoping for many more days like that since many of us were wondering if this severe winter would ever end.
For 190 days, the last thing that dairy producers wanted to think about was heat stress abatement. However, as we enjoy the warmer temperatures heading into May and June, we need to start thinking about our heat abatement strategies for our dairy cows.
For the most part, humans function best in warmer weather since our ideal thermoneutral zone is between 65 to 85 degrees. For dairy cattle, it is a different story since they are cold-weather animals.
Heat stress and its effect in dairy cows
Dairy cows function best in the thermoneutral zone of 25 to 65 degrees and certainly can do well in temperatures well below zero as long as management and facilities are in place to minimize wind chill. In other words, cows can tolerate very cold temperatures and do quite well. However, cows are dramatically affected once the temperature-humidity index (THI) goes above 75 degrees. What may feel comfortable to us may actually be imposing heat stress in our dairy herds. As the THI rises above 90 degrees, significant heat stress signs will be very noticeable and costly.
Decreased milk production is the most immediate and financially painful result of heat stress. Cows simply eat less and, in combination with expending energy to keep cool, less milk is produced. During severe heat stress, milk production can decrease as much as 25 percent.
Increased mastitis rates may be another immediate effect of severe heat stress. Heat stress effects just don’t end there. We see residual heat stress effects well into October and November even though heat stress is not an issue. Residual heat stress effects occurring in the fall season include low pregnancy rates, foot issues, poor fresh cow starts and body condition challenges.
Obviously, these immediate and residual effects of summer heat stress can and will have a significant effect on the dairy’s cash flow and profitability if not correctly addressed. It is important to review your heat abatement plan before the summer season and make the necessary changes. A good method to review your heat abatement plan is the 3-M approach: mechanical considerations, metabolic considerations and management considerations.
In this article, we’ll focus on the mechanical considerations and the things you can do now to prepare for warm temperatures. Look for a future discussion on metabolic and management considerations.