Heat Stress Management Strategies

Tara Jo Bina
Countryside Feed Nutrition
 
June is here, and summer weather has made its presence known! Heat and humidity can have many impacts on both lactating and dry dairy cattle including elevated body temperatures, increased respiration rates, depressed feed intake, and reduced milk production. These effects occur when the temperature humidity index (THI) exceeds 68. Fortunately, there are effective strategies to combat heat stress that include combining management and nutritional adjustments. 
 
Air Movement
There are few things that are more miserable than dealing with hot, stagnant air. Circulating air by turning on fans is one way to help cows combat heat stress. As a rule of thumb, fans should be running when barn temperatures are above 60 – 65°F. Keep in mind that these temperatures can occur day or night. Fans should be installed to circulate air over lying areas (free stalls or bed packs) as these areas are commonly  5 – 10°F hotter than temperatures of feed alleys! Other areas fans can be useful in are feed alleys (as long as they do not blow water from sprinklers onto feed) and holding areas.
 
Water

Recommended Sprinkler Intervals
Temperature	Interval	Time on	Time off
72 – 75°F	15 min	3 min	12 min
82 – 85°F	10 min	2 min	8 min
90°F +	5 min	1 – 2 min	3 – 4 min

Access to fresh, clean drinking water is crucial for cows under heat stress and should be offered in both pens and return alleys. Cleaning waterers often to ensure water available to cows is fresh and palatable is a good practice.
 
 Water can also be used in sprinkler systems in feed alleys and holding pens to help with heat stress. 
    
Feeding Times
Hot temperatures and heat stress commonly cause reduced feed intake. One way to combat this effect is to adjust feeding schedules. Feeding a higher percentage of the daily ration at night allows cows to eat when temperatures cool off.
 
Ration Changes

• Ration preservers

As temperatures warm up, feed becomes an ideal environment for yeasts and molds. Not only can the presence of these microbes reduce intake, the byproducts they produce can be harmful to cattle. Propionic acid-based products, such as calcium propionate, can be added to rations to reduce growth of yeasts and molds, keeping feed fresh and extending bunk life.
 

• Electrolytes

Electrolytes are a good first step in helping cows combat heat stress. Among many other bodily functions, these substances promote hydration by aiding in water absorption across tissues. Products used to increase dietary cation anion difference (DCAD) in rations commonly contain sodium and potassium, therefor are not a good option for transition cows when maintaining a negative DCAD is important.
 

• Vasodilators

These feed additives help cows increase blood flow to their extremities by “opening up” blood vessels allowing heat to escape.
 

• Osmolytes

This group of compounds encourage water intake and absorption, allowing cows to hydration at the cellular level. Animals that are properly hydrated have an increased ability to deal with heat stress. 
 
Heat stress is a serious concern in the summer months. Contact your Countryside Feed sales representative to discuss options for combating heat stress in your dairy cattle!