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Prepare calves for 2018’s summer heat

Ron Martin for Progressive Dairyman Published on 24 May 2018

If you haven’t already planned for managing heat stress in calves this summer, there’s no time to waste. Just like cows, calves are susceptible to heat stress at higher temperatures, which can affect both health and performance.

In extreme cases, heat stress may lead to severe dehydration or death. Even in less extreme cases, calves must expend extra energy to keep cool in the summer months.

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According to the University of Minnesota Extension, during the spring and summer months feed intake typically drops, and maintenance energy is estimated to increase 20 to 30 percent. Reduced intake plus increased energy expenditure can lead to slower growth during the summer months which can, in turn, reduce overall lifetime performance.

It is important to take the appropriate steps to prevent heat stress and monitor calves throughout the summer months for signs of heat stress, including the following:

  • Increased respiratory rates
  • Heavy breathing
  • Increased body temperature
  • Poor appetite

High ambient temperature, high relative humidity and excessive radiant energy are all conditions that set the stage for heat-stressed animals. Furthermore, not only are calves at risk for becoming dehydrated in hot weather, but the heat can also result in impaired immune function as well as the growth of infection-causing bacteria.

Fortunately, there are a number of ways producers can work to prevent calves from becoming heat stressed in the first place. Penn State Extension offers the following tips for keeping calves cool in hot weather:

  • Provide shade
  • Move more air
  • Offer plenty of water
  • Keep grain fresh
  • Consider inorganic bedding
  • Work calves in the morning
  • Consider feeding more milk replacer

The Dairy Calf and Heifer Association’s (DCHA) Gold Standards for raising calves recommends housing for all calves and heifers be clean, dry, appropriately ventilated, sheltered from inclement weather and equipped with shade in outdoor housing settings.

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Additionally, DCHA recommends the effects of heat stress be minimized by providing shade – 80 percent shade cloth suspended at least 7 feet above hutches – orienting hutch rows east to west to maximize shade and improving ventilation by elevating the backs of hutches.

Many of these recommendations require only simple adjustments to keep calves more comfortable. Repositioning hutches to better facilitate air flow can help reduce the internal temperature of the hutch, which may otherwise become much hotter than the temperature outside.

Facing the hutches to the east, adjusting the amount of space between hutches and placing cement blocks under the back edge of the hutch for elevation can increase air flow and reduce internal hutch temperature.

Using inorganic bedding such as sand instead of straw can also help dissipate heat more quickly. To further reduce stress, producers can move stress-inducing activities such as dehorning and vaccinating to the cooler hours of the morning. Feeding more milk replacer can also help supplement energy lost due to decreased starter intake.

Most importantly, calves should have access to fresh, free-choice water throughout the day in order to stay hydrated.

In addition to monitoring for signs of heat stress, producers should also be watching for signs of dehydration. Typical indicators include sunken eyes, dry mouth and nose, weight loss, fast or very slow pulse, cold ears or cold legs.

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A skin tenting test can also be performed by pinching the folds of skin on the neck of the calf and observing how long the skin remains tented. Two to six seconds means the calf is moderately dehydrated, and more than six seconds indicates severe dehydration.

Dehydration due to scouring may also prove more deadly in the summer heat. If calves become dehydrated due to heat, scouring or both, oral rehydration solutions containing electrolytes should be administered as soon as possible.

Early electrolyte solution treatment protocols addressed electrolyte balance and partial energy balance. The latest treatment protocols address electrolyte balance, compensate for metabolic acidosis resulting from long-term fluid losses, address energy balance and partially address protein balance by incorporating milk or milk replacer feedings between electrolyte treatments.

Probiotics have been added to many diarrhea treatment protocols with variable but generally good success. Probiotics have also been reported to be useful in preventing E. coli diarrhea.

A good oral rehydration solution should contain sodium, glucose (an energy source), glycine (to enhance absorption of glucose), alkalinizing agents such as bicarbonate to decrease metabolic acidosis and other electrolytes such as potassium and chloride. Some solutions also feature gelling agents to coat inflamed intestinal mucosa and slow down the passage rate of the solution in order for the intestine to better absorb nutrients.

In addition to the electrolytes sodium, potassium and chloride, some electrolytes also contain probiotics (beneficial bacteria or yeast), specialized egg proteins, vitamins and minerals to rehydrate calves and support overall health.

Oral electrolyte products can also provide daily nutritional supplementation and extra energy along with the electrolytes necessary to keep calves hydrated. Electrolyte powders may be used for daily maintenance feedings and even for reduced rate inclusion with milk or milk replacer for specific conditions.

However, it is essential to always follow specific package instructions, since the ingredients found in oral rehydration solutions are beneficial only in the specified amounts and can be detrimental if over-administered. Except for products specifically labeled for reduced rate inclusion with milk or milk replacer, electrolyte solutions should not be mixed with milk or milk replacer, and full potency electrolyte powders should not be added to milk or milk replacer.  end mark

References omitted but are available upon request. Click here to email an editor.

Ron Martin is the product manager with Bio-Vet Inc.

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