Reduce Heat Stress in Cattle

Tuesday, July 12, 2011

agriculture.com

With temperatures expected to reach dangerous highs this week in the middle of the country, Iowa State University (ISU) Extension beef veterinarian Grant Dewell urges beef cattle producers to prepare for these weather conditions to maintain herd health.

Facts you should know

  • Feedlot cattle are at higher risk than pastured cattle, which have the ability to seek shade and avoid radiant heat from dirt or concrete surfaces.
  • Temperatures exceeding 80 degrees F cause physiologic stress on cattle. Though they are not at risk of dying, their health can deteriorate.
  • Compared to other animals, cattle cannot dissipate their heat load effectively due to their inability to sweat.
  • Cattle’s core temperature peaks 2 hours after peak environmental temperature.
  • It takes at least 6 hours for cattle to dissipate their heat load.
  • Black cattle and heavy cattle and respiratory compromised cattle have an increased risk of heat stress, and higher chances of death.

Managing the heat

Careful monitoring: Don’t work cattle at all in high heat. Finish working cattle before 9 to 10 a.m. during the summer. Do not work cattle in the evenings after it has cooled off. It takes at least 6 hours for cattle to recover from their heat load. Cattle should not wait in processing areas longer than 30 minutes.

Water requirements: Cattle lose water more quickly from increased respiration and perspiration when it’s hot. Consuming water is the only way cattle can reduce core body temperature. Cattle need 3 inches of linear water space per head during the summer. The supply should be able to deliver 1.1% of body weight of the cattle per hour. A 1,000-pound animal needs about 1.5 gallons of water per hour. Introducing extra water tanks before extreme heat will allow cattle to become accustomed to them.

Feeding changes: Cattle should not be fed in the morning when body heat will peak when environmental temperatures are also at their highest (midday). Cattle should receive at least 70% of their feed 2 to 4 hours after the day’s peak temperatures. Changing the ration is controversial, but the general recommendation is to reduce the diet energy content of feed by 5 to 7%.

Shade and ventilation: There should be 20 to 40 square feet of shade per animal. Shade structures are most adequate when they have an east-west orientation and are more than 8 feet off the ground to heighten air movement. Removing tall vegetation within 150 feet of the feedlot pens will also expose cattle to more air movement.

Cooling techniques: Sprinklers can cool cattle during times of stress by increasing evaporative cooling and reducing ground temperature. Sprinklers are adequate when they wet the animal and not just mist the air. Sprinklers should not interfere with drinking water supply. Use sprinklers intermittently to avoid mud and increased humidity. Assess water temperature: thermal shock from too cold of water can kill cattle that are extremely stressed. Once sprinklers are utilized, they should be continued until the heat is over.

Fly control will also reduce cattle stress. Biting flies cause cattle to bunch up, decreasing cooling. Minimize breeding areas for flies and apply insecticides to decrease fly populations before heat stress.

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