By Jennifer Malkus, DVM – Sioux Nation Ag Center
As the weather gets warmer, cows can become heat stressed which can result in a decrease in milk production and difficulty getting pregnant. Cows can show signs of heat stress at temperatures as low as 72 degrees F if the humidity is high. To combat this, it is often important to start heat abatement earlier than you might think. The three proven heat abatement methods are shade, air flow, and water.
While most dairy cows are housed in free stall or pack barns, it is important to realize that at different times of the day the sun may be coming into the barn though the sides and increasing the temperature. East-west oriented barns are less affected by this than north-south oriented barns. In the mornings more shade is needed on the east side of the barn and in the afternoon and evenings, the west side needs more shade. One of the easiest ways to accomplish this is to have curtains on both sides of the barn that can be easily raised and lowered depending on where the sun is. It is important to remember that curtains will also block natural air flow. They should be used only when necessary to block the sun, and more fans may be needed to overcome a decrease in natural air flow.
Air in a barn should be exchanged every minute or less in warmer weather. This is essential to remove gasses, moisture and heat from the cow’s environment. Common ventilation methods in dairy barns include cross ventilation, tunnel ventilation and natural ventilation. These ventilation types can allow for proper air flow and exchange. Depending on temperature, the ventilation system alone may not be adequate to remove heat from the barn. To overcome this, fans may be added to increase turbulent air flow around cows, which enhances evaporation and heat transfer. Air speeds of 3-5 mph are adequate to reduce heat stress. A wind speed measure should be taken at various locations throughout the barn to ensure there are few dead air zones. High velocity fans placed in a row should be angled slightly down and be no more than 10 times the fan diameter apart, and side by side between 2-3 diameters apart. Low velocity fans can be placed directly over animals at no more than 2 times their diameter apart. Remember that the holding pen will also need plenty of fans to cool cows waiting to be milked.
Clean drinking water needs to be readily available and accessible at all times of the year, but it is especially critical during the warmer months. Ensure that cows have access to water at multiple places in their pen and that the waterers are large enough to allow multiple cows to drink at a time. Waterers should also be available on the walk to the parlor and as cows exit the parlor. In addition, many farms employ the use of sprinkler systems in the free stall pen and in holding pens. Sprinklers need to thoroughly soak the cow for 1-3 minutes, and fans will aid in evaporation which lowers the cow’s core body temperature. A fine mist constantly on will not have the same effect and can cause the cow to retain more body heat.
Other ways to ensure happy, cool cows during the summer include not overstocking the free stall pens, allowing adequate space in the holding pens of at least 15 square ft per cow, and limiting their time in the holding area to 60 minutes or less. Having proper shade, air flow and water access will make a huge difference in reducing heat stress to cows all summer long.