Have a plan for heat stress

Summer is fast approaching, bringing with it the promise of hot weather and added stress for dairy cows. The symptoms of heat stress are easy to recognize. Rapid, shallow breathing with respiration rates of at least 60 breaths per minute, open mouth panting, extended tongues, and drooling are all indicators of animals experiencing heat stress. Less apparent are the effects this has on the cow internally.

A dairy cow undergoing heat stress is in survival mode. Her feed intake can decrease by 35%. Instead of mobilizing fat (which generates more heat), her body chooses to degrade protein. Protein degradation produces urea as a byproduct. Some of this urea can accumulate in the uterus resulting in reduced fertility and the remainder must be removed by the kidneys—a process that requires her to use more energy.

On the reproductive side, not only can fertility be reduced by the increased urea, but embryo survival is compromised at body temperatures exceeding 102.2°F, particularly in the first week after insemination. In the end she is not able to meet the energy demands required for maintenance and production; production is sacrificed and embryo survival is greatly reduced. Is it any wonder that production losses of 20 to 30 percent and single-digit pregnancy rates are common during the summer months?

The good news is you can mitigate some of these losses through cow cooling. Providing shade should be priority number one. Solar radiation can raise the temperature humidity index (THI) by 6 to 9°F. Also, make sure adequate drinking water is available.

Provide 3 to 4” per cow of linear tank perimeter. Keep in mind cows will consume 30 percent of their water upon exiting the parlor; make sure adequate space is available for all cows to drink upon exiting the parlor. Sprinklers and fans are also critical for effectively cooling cows. Research from University of Arizona shows that fans alone are not effective at cooling an already hot cow. This is not to say that fans are not beneficial. Fans can still increase airflow and delay the rise in temperatures in a barn. However, if you really want to cool cows and have a major impact on heat stress, water is critical.

Sprinklers and fans in the holding pen are a great place to start. The holding pen is the most stressful location on the farm and can be one of the best locations to add sprinklers. However, if sprinklers are added make sure to include fans or you can create a “sauna” effect with water alone.

Sprinklers over the feedbunk are the next priority.

Fans over the freestalls and the feedbunk should be next. All fans should be spaced so that at least 5mph wind speeds can be measured underneath the next fan. New recommendations are to turn fans on at 65°F and sprinklers at 68°F. Also, keep in mind fans need to be cleaned. Dirty fans can reduce fan efficiency by 40 percent.

For more information on recommended cooling systems contact your local Dairy Extension Agent.

Source: Beverly Cox, Extension Agent, Franklin County, Virginia Cooperative Extension

Further reading

Efficient milk production under heat stress conditions

Written by: Israel Flamenbaum

Heat stress is now considered to be the cause of the largest economical loss to the world’s dairy sector. The reasons for this are global warming, the increase in milk output per cow and the “immigration” of dairy sectors from temperate to tropical and sub-tropical regions, where the demand for milk in most cases is increasing.

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Further reading

Effect of heat stress and cooling on cows’ fertility

Written by: Israel Flamenbaum

Cow fertility tends to decline in the summer in hot and even temperate climates. Heat stress negatively affects all stages of the cow’s fertility, among them the manifestation of “heat signs”, conception and maintenance of pregnancy.

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Further reading

Heat stress

Written by: Mary Beth de Ondarza

Heat stress increases maintenance energy requirements and it lowers dry matter intake, making it difficult to meet energy needs. Therefore, feeding management and forage quality become critical during heat stress.

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Further reading

Calves and heat stress

Extreme heat may accelerate the calf’s nutritional and hydration needs by 20 to 30 percent. Calves dissipate heat by panting and lose valuable hydration by this. Even mild dehydration of 1 to 5 percent loss of body weight from water loss can reduce metabolic efficiency and impair calves’ ability to regulate their own body heat.

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Further reading

Warm weather changes calf management

Heat stress can be a problem for calves that dissipate heat by panting and lose valuable hydration via this route. We need to manage calves to reduce overheating and, at the same time, improve water management. Here are some summertime tips:

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Further reading

Heat stress abatement improves feed efficiency of high yielding cows in the summer

Written by: Israel Flamenbaum

A lot of information has been published in last three decades on the negative effect of summer heat stress on the productive and reproductive traits of the high yielding cow. Very limited information existed, however, up until the last few years, on the effect of heat stress on the feed efficiency of cows (as estimated by the feed to milk ratio).

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Further reading

"Summer to Winter Ratio" - A tool for evaluation of the effectiveness of farm’s heat abatement treatments

Written by: Israel Flamenbaum

Summer conditions make the implementation of cooling systems in the dairy farms an important tool for efficient milk production. In cooperation with the "Israeli Herd book" data, a new index was developed, called the summer: winter ratio. This index serves as an indicator for characterization of the effectiveness of farmer's efforts to reduce summer negative impact on cow's performance. In the following article, the use of this index will be described, and the achievements of the Israeli dairy sector in combating heat stress in the last 15 years will be presented.

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Further reading

Seven practical heat stress abatement strategies

Written by: Craig Thomas

Heat stress abatement is a critical dairy management strategy for all dairy producers. Properly applied, these seven heat stress abatement strategies can minimize the harmful effects of heat stress on dry matter intake, milk production (volume and components) and reproduction. Be sure to include every animal on your dairy when considering heat stress abatement strategies. Heat stress affects not only high producing milk cows, but also dry cows, heifers and calves. Minimize heat stress in your dairy cows by following these strategies.

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Further reading

Coping with summer weather

Written by: John F. Smith Dick Dunham Gerald Stokka Jeff Stevenson Joe Harner Matt Meyer

Heat stress occurs when a dairy cow’s heat load is greater than her capacity to dissipate the heat. Effects of heat stress include: increased respiration rate, increased water intake, increased sweating, decreased dry matter intake, slower rate of feed passage, decreased blood flow to internal organs, decreased milk production and poor reproductive performance.

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Author

Monica Wadsworth

Monica Wadsworth
85 articles

Writer at Milkproduction.com

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Milkproduction.com

Milkproduction.com

More links to heat stress articles further down on the page

The dairy farms

Don Mateo, Argentina - Knowing the value of knowledge

Published: 6/29/2011

Knowledge and animal welfare are the main challenges for Argentina’s dairy farmers today, according to Raúl Martinich, owner of Don Mateo dairy farm in San Jorge, Santa Fé province in Argentina.

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