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.

These are signs that your calves are suffering from heat stress:

  • Increased water consumption
  • Lethargic, “lazy” behavior
  • Standing rather than lying
  • Panting, sweating
  • Increase in disease; monitor incidence of scours
  • Reduced feed intake and/or growth
  • Rectal temperature higher than 102° F

Housing is critical. Use shade cloths over rows of calf hutches and prop up the back end of the hutch to facilitate air movement. For calves housed indoors open windows, lower side curtains and consider fans.

Remove bedding more frequently. Bedding retains heat if excessively soiled with urine and manure.

Water management is crucial. Make sure that water buckets are large enough so that they don't run dry during a 24-hour period. Locate buckets so calves can't spill starter grain into them. Don't expose buckets to direct sunlight which overheats water and encourages algae growth.

Sanitation is critical. Dump water buckets daily to maintain freshness. Wipe buckets with a dilute chlorinated solution at least once a week to reduce alga growth. Don't use the same bucket for milk and water. Milk remaining in the bucket allows bacteria to grow and may encourage organisms responsible for abomasal bloat or other diseases.

Consider more liberal use of electrolyte solutions. In warm weather, calves are more prone to dehydration. Scouring calves should receive oral electrolyte solutions liberally, particularly during mid-day. Administer electrolytes by bottle early in the course of diarrhea because solution absorption is likely to be better than if given by tube.

Keep calf starter fresh. Add as much as they will eat each day, and feed refused starter grain to older heifers.

Calf hutches

More than 1,000 dairy calves throughout the Midwest have died during the a two-three week period in July 2012 as a result of heat stress. The calves were between 2- and 7-days-old and had been housed in outdoor calf hutches with no shade, according to a news release.

Prefabricated plastic hutches are a widely favored method of housing dairy calves because they are durable, portable, easy to clean, and allow producers a cost-effective way to house calves individually. However, many currently-available plastic hutches can average 5 to 10°C higher than wooden ones. Even with open ventilation slits or windows, airflow through many hutches is suboptimal, allowing heat, humidity, and carbon dioxide to accumulate. According to a study from Washington State University you can decrease the temperature inside a plastic calf hutch if you elevate the hutch by inserting a block of concrete (20 × 20 × 41-cm) at the back.

Sources: Dairy Calf & Heifer Association, University of Illinois, Washington State University, Wisconsin Department of Agriculture