Heat Stress in Calves

With the temperatures warming up in this part of the world, many dairy producers are focused on implementing heat abatement practices. Usually, most time and energy are put into cooling cows early in lactation, because this group of animals has an immediate effect on farm income. However, it is important to not forget that other groups of cattle also experience heat stress, and long-term benefits will come from cooling all groups of cattle.

As the temperature heats up don’t forget about your calves! There is limited data regarding heat stress in young calves, however we do that they do start to expend more energy when the temperature climbs above 78 degrees F (25.5 degrees C).  

Signs of heat stress include;

• less movement
• faster breathing rate
• open mouthed panting
• decreased feed intake
• increased water consumption

Act to mitigate heat stress to prevent a decrease in calf performance. An increased body temperature will result in decreased grain intake, decreased feed efficiency, decreased rate of gain, decreased rumen development, and challenges for the immune system.

Maternity Pen and Colostrum Management

Research studies show that heat stress for calves, is a challenge even before birth. Calves born to heat stressed cows have lower rate of IgG absorption, lower weaning weight, and lower chance of survival. It is very important to cool dry cows to avoid these detrimental effects on the calf. Use fans, misters, shade and nutritional strategies to help mitigate heat stress.

High temperatures also mean greater growth of pathogens. Clean the maternity, and calf processing areas regularly. Re-evaluate equipment cleaning protocols to ensure that equipment is not infecting calves with disease. 

Colostrum quality often declines during the hot seasons. Monitor quality and IgG levels to ensure calves are receiving adequate passive transfer. Routinely sample colostrum for coliforms and standard plate count, feeding dirty colostrum will set the calf up for failure. Click here for more details on guidelines for clean colostrum and newborn calf care.

Housing and Environment

Housing arrangements need to be adjusted in the warmer months to allow for increased air low and reduction of CO₂. If calves are housed outside in hutches, open as many vents as possible. To allow air to circulate between the hutches, place them at least 4 feet apart and allow 10 feet between rows, and face hutches so they will catch the prevailing winds. Another helpful practice is to prop hutches up to allow increased air flow. This can be done by elevating the back edge of the hutch 6-8 inches off the ground. Ensure that bedding does not impede the air flow.

Plastic huts can retain heat and actually make the temperature inside greater than that of the outside temperature. Research has shown that hanging a shade cloth about four feed above the hutch will reduce the inside temperature 3-4 degrees and the calf’s body temperature by 0.5 degree when compared to calves housed in plastic hutches with no shade. Another option would to be to cover calf hutches with a reflective cover to reduce the overall temperature of the hutch, and reduce stress on the calf.

Calf barns should be opened up as much as possible. Once temperatures reach 75 degrees F (23.9 degrees C) curtain sidewalls can be completely opened.  Also consider using additional fans, or even positive pressure tubes designed for summer ventilation rates.

Nutrition

During heat stress, calves usually show a decrease in feed intake, however, although they have less desire to eat, their energy requirements for maintenance actually increase as much as 20-30%. This leaves the animal with a depressed immune system and much more susceptible to disease and dehydration. Visit with your nutritionist and consider increasing feeding frequency during the summer months to help calves consume enough energy.

Keeping fresh, clean water in front of calves is really important. Healthy calves under heat stress will drink between 6-12 quarts of water daily just to maintain normal hydration. Sick calves under heat stress may require up to 20 quarts to correct dehydration. In the warmer months implement an aggressive electrolyte therapy plan. Electrolytes can be given only to sick animals, or in the case of heat stress of midday bottle of electrolytes can be beneficial for all calves to provide hydration.

Management

Always use good animal husbandry practices when handling calves. During the warmer months complete routines such as vaccination, dehorning, and pen moves during the cooler parts of the day, as to not contribute to heat stress.

Heat stress causes immune system depression. It is essential to maintain a clean environment for calves during this time. Warm, damp, soiled areas are the ideal environment for bacteria, parasites, and other harmful organisms to grow.  Keep all housing and feeding equipment clean and disinfected. Allow wet areas to dry before re-bedding moving new calves to the area.

Implement a heat stress management plan now for your calves, and it will pay off for years to come!

Written by: Mariah Gull, M.S.