The impact of heat stress on dairy cow health and performance can be devastating, but the solution can be simple: Minimize heat gain and maximize heat loss. You can achieve this with evaporative cooling strategies, ample amounts of cool, clear water and the right nutrition to replenish lost nutrients.
Dairy Technical Services Manager
Arm & Hammer Animal and Food Production
Hot weather reduces feed intake and rumination, ultimately hampering milk production and reproductive performance. So, how do you protect your cows? By preparing them.
PUT COWS IN A COOLING CYCLE
Heat stress happens when the cow’s heat load is greater than her capacity to lose heat. When cows are hot, they pant and sweat, but neither is nearly effective enough to expel the large amounts of heat created by cows. The formula to alleviate heat stress is simple: soak, dry, repeat.
Evaporative cooling is the most effective method for expelling heat from the cow. In this process, cows are soaked with water, then air movement over the cow creates an evaporative effect that pulls heat from the body, increasing cows’ natural evaporation rate to improve cooling.
In the past, cows have stood for long periods of time under misters to get cool. That method has improved and the process now includes large droplets of water sprayed over the entire back of the cow long enough for water to get under the cow’s hair and to the skin.
It’s important to create a cooling cycle that includes a soaking period followed by drying time. Create enough water volume to cover the cow in 30 seconds or less, timing it so about 80% of the cow dries before soaking again. To achieve this level of dryness in a short amount of time, it takes good air flow—and that requires fans.
Adding a greater number of fans in the barn creates more consistent air flow on top of cows with fewer dead spots. Use fans with good spread and throw to get the best coverage and best return on evaporative cooling benefits.
Technology at this stage also helps make the soaking process more efficient. Sensors can recognize if a cow is in a lockup and turn off the nozzle if no cow is present. Controllers can break the barn into quadrants and manage soaker times long enough to get cows soaked, then turn themselves off. They can also be set to turn off when no cows are present, such as when a pen is in the holding area.
One common area where heat stress affects cows is the holding area. Cows can quickly spike high temperatures while standing packed into tight areas during high THI periods. Soakers and fans play an essential role in ensuring both cooling and adequate ventilation in these close quarters.
SUPPLY COOL, CLEAR WATER
Evaporative cooling can help remove heat from cows and alleviate heat stress, but providing large amounts of cool, clear water is also key. Consider these points when providing water to cows:
• Provide ample and readily available access to water troughs by creating five linear inches of trough space per cow and ensure cows are never more than 50 feet from a water source.
• Keep troughs clean, but don’t over chlorinate. Cows are creatures of smell and will avoid water troughs with a strong chlorine smell.
• Set the proper float level to allow for maximum fill.
One of the best things you can do to provide cows with an ample supply of water when they want it most is to install a water source in the parlor return lane. Cows will consume 30%-50% of their daily water needs within an hour after milking, so nearly every cow will stop to drink when walking away from the parlor. The process will also improve feed intake when she gets back to the feed bunk.
TUNE UP YOUR NUTRITION STRATEGY
Just like your cooling equipment needs the occasional tune-up, so does your nutrition strategy. Cows are prone to potassium deficiencies during heat stress. Although milk is known for high levels of calcium, potassium levels are actually higher. Potassium is also the main component of sweat and cows lose it quickly through increased perspiration and urination during hot weather.
Fresh cows require higher levels of dietary potassium, and research shows that cows are often potassium deficient for the first 10 weeks of lactation. That’s why it’s important to feed supplemental potassium. Achieving a positive DCAD (Dietary Cation-Anion Difference) level and increasing the potassium component can help replace what is lost during milk production.
Increasing potassium level to 1.7%-2% in high-producing and fresh cow diets helps maximize production and improve cow starts during heat stress. Potassium sources such as DCAD Plus from Arm & Hammer™ have the potential to boost fat-corrected milk production by as much as 8.5 pounds per day.
In addition to increasing levels of dietary potassium, adding yeast, buffers and energy density to the ration can also play an important role in mitigating the impact of heat stress.
It is possible to help your cows beat the heat. With evaporative cooling techniques and water can help minimize heat gain. And ensuring your ration is properly formulated can reduce the stress placed on cows from warm weather. Together, these strategies can help optimize milk production in the face of heat stress.
Research available on request.
About Dr Ruby Wu
Dr. Ruby Wu has extensive experience across the dairy industry, including her current role as dairy technical services manager at Arm & Hammer Animal and Food Production. Dr. Wu holds a bachelor’s degree in animal science from China Agricultural University, a master’s degree in dairy nutrition from the University of Georgia and a Ph.D. in animal science-dairy nutrition, also from the University of Georgia.
