Animal Handling During Heat Stress - Dairy

Tasks Requiring Animal Movement

The THI chart is an important consideration when moving cattle. To prevent cattle losses during handling, refer to the THI chart to determine the likelihood of heat stress during high temperature and humidity conditions. 

However, dairy animals can experience discomfort and poor welfare associated with heat stress in milder weather before production losses occur.  

Limit the length of time animals spend in headlocks or other handling equipment. Their stress from confinement may compound with the stress from hot environmental conditions. To prevent added heat stress, handle animals during the early morning hours before the temperature rises to the risky THI level. When THI is 72 or higher, consider postponing animal handling-related tasks that can be performed in cooler weather. An animal’s internal temperature peaks approximately two hours after the environmental temperature peaks, and it takes the animal four to six hours to lower its temperature back to normal.

If possible, the evening hours should be left for the animals to cool down and not used for handling unless necessary.  Cattle will eat more and show reproductive activity during the cooler evenings. If possible, do not interfere with their comfort during this time.

Use caution while vaccinating cattle during high THI levels. A typical reaction to a vaccine is a mild fever (increase in core body temperature by one or two degrees). Vaccine-induced heat stroke may occur when this elevated core body temperature coincides with high THI levels. To prevent induced heat stroke, vaccinate early in the morning. This practice enables the cattle to control their immune response to the vaccine before the ambient temperature rises. Another option is to vaccinate cattle in the evening, six hours after the peak daytime temperature. Using this option, the normal vaccine reaction (an increase of one or two degrees of the cattle’s internal temperature) will occur during the cooler evening hours. 

Extra care should be taken if the evening temperatures do not drop below 70°F as the cattle cannot recover before another day of heat and humidity. The longer the heat stretch lasts, the more stressful it is on the cattle. 

When animals become nervous and stressed, their core body temperature naturally rises. To keep this temperature down, always remember to use low-stress handling techniques. Move cattle slowly, calmly, and for only short distances, if possible. Plan and avoid any unnecessary movements or stressful handling. 

Make a note of any compromised cattle. Cattle that are sick, lame, heavy, weak, recently calved, or newly purchased are all at high risk for heat stress. Watch these cattle closely for signs of heat stress and take extra precautions to cool them down if needed. 

Check and clean waterers to ensure cattle have adequate clean water. Check hoses, pumps, floats, and all parts of the water supply system to ensure water is always available. In the summer heat, cattle’s water intake increases, and many may drink simultaneously. Ensure the refill rate is adequate, enabling all cattle to drink. To ensure proper access to water, consider adding additional temporary tanks if needed. 

Cattle will also congregate around the waterer to capture evaporative cooling from the water. This leads to manure build-up and flies around the waterers. Remove manure build-up around water tanks and locate the tanks in a high, dry area. If puddling occurs at the base of the water tank, move the water tank to higher ground.