Keeping cows cool from heat stress

By Rainey Rosemond, Penn State Extension Dairy specialist

A lot dairy cows can experience heat stress, which caused by blend of solar heat and internal heat energy generated by a cow's feed digestion. Most common environmental drivers of heat stress are temperature and humidity. The stress threshold for dairy cows has been documented to begin at as low as a temperature humidity index 68°F, which can also be reached at low temperatures.

Common signs of heat stress include increased respiration rate, panting, reduced milk yield, reproductive performance, modified drinking and feed intake, increased standing time and shade seeking, and decreased activity and movement. However, many areas of production can be impacted by heat stress, Below are four management strategies that you can focus on the reduce heat stress in your herd.

Water Intake

Water intake should be your top consideration looking to reduce or manage heat stress. Fluctuations in water intake can limit a dairy cow's ability to regulate her body temperature. High-producing dairy cows need about 25 to 35 gallons of water per day. A recent Penn State study found that water intake by a heat-stressed dairy cow can increase by 1.47 pounds per °F above the minimum ambient temperature.

To encourage adequate or increased water intake in your herd, proper maintenance of water bowls is needed. Water troughs should be cleaned of debris such as the total mixed ration or manure daily. Your barns watering areas should also be cleaned bi-weekly with a diluted chlorine solution to ensure grime is not allowed to build up. A cow's water intake is typically greatest immediately following milking. Experts suggest that producers add water troughs for animals to access as they return from the parlor.

Feed Intake

According to research, dairy cows consume less feed as environmental temperatures increase and to combat the effects of reduced feed intake, good feed management practices should be implemented.
Farmers should maintain feed present and in front of cows for about 24 hours a day. A good practice to do daily during hot weather is checking if the feed feels hot to the touch. In addition, ensuring refusals are scraped out daily and fresh feed is delivered multiple times per day will help maintain normal feeding behavior.

Producers should also walk their bunks daily to observe feeding patterns. Depending on tractor direction, feeding patterns, and feed-out rates the entirety of a bunk might not be used. It's easy to overlook, covering all available feed bunk surfaces will help reduce competition for feed and cow-to-cow interactions. Also monitor how feed is pushed. If the feed is only redistributed in one direction with each push, it is important to ensure that feed bunk space isn't limited by feed placement.

Pasture Management

As the weather warms up, it is common to put dry cows, heifers, and lactating cows out on pasture. While pasture provides cattle opportunities to socialize and exercise, it doesn't come without risks to animal health, especially depending on the time of day. Dairy cows naturally seek shade when experiencing heat stress. So, farmers should make sure animals have adequate shade, whether its trees or shade structures helps them alleviate heat stress. Another important part of providing adequate shade on pasture is offering enough shade coverage options to avoid groups of cows bunching up under one structure making the the ground sloppy, which could lead to dirty animals and new mastitis infections. You should also make sure cows housed on pasture have access to clean water and ensure water trough's floats and water lines are operating especially, if you have multiple paddocks being grazed.

Lameness and Pain

Heat-stressed dairy cows will increase their standing time in an effort to increase surface area for heat abatement, which puts them at risk for lameness. Alterations in nutrition can also change cows dry matter intake and results in an imbalance in the weight of nutrients consumed. However, an increase in standing time reduces lying time, which also reduces rumination time, and alters nutrient digestion. Farmers should prioritize cow comfort and hoof health during heat stress conditions.

Heat stress has been documented to impact cattle welfare and performance for over a decade. While a decline in production is seen on many farms, you can control how much a production drop-off can be easily mitigated by properly managing shade areas in pastures and encouraging your herd to keep their feed and water intake during hot days.