Heat Stress in Calves: Water, Growth, and Gut Health

Heat stress in calves is a bigger issue than most people realize. While cows often get the most attention in summer because of the impact heat stress has on milk production, don't forget about the calves!

Young calves can also be strongly affected by hot weather, especially when heat combines with humidity. Recent research shows that heat stress raises body temperature and breathing rate in calves, increases water intake, reduces growth efficiency, and can even disturb gut barrier function and contribute to inflammation.

Hydration

One of the most consistent signs of heat stress in calves is increased water demand. As temperatures rise, calves drink more to support cooling and hydration. Recent studies suggest that season of birth may additionally influence voluntary water intake as well. That means water access is not a minor detail; it is one of the first lines of defense against thermal stress. 

Offering water early and often could be the most cost-effective and welfare-promoting method for abating heat stress.

Growth

Heat stress also affects growth. Studies in pre-weaned dairy heifer calves in a humid continental climate showed that warm conditions can reduce weight gain and alter physiological indicators.

At the physiological level, heat stress forces calves to shift nutrients away from growth and toward survival. Research has shown higher respiration rates, higher body temperatures, lower energetic efficiency, and signs of increased intestinal permeability and inflammation. A proteomic study in heat-stressed Holstein cattle further suggests that heat stress triggers widespread changes in blood proteins linked to structure, signaling, and coagulation, underscoring how broad the biological response can be.

Mitigate Thermal Stress

The practical response is straightforward: give calves consistent access to clean water, provide shade, improve airflow, and minimize additional stress during hot periods. Heat stress cannot always be eliminated, but its impact on calf health and growth can be reduced with good management.

In addition to environmental adjustments certain changes in feeding programs could provide additives to biologically aid the calf in resilience towards heat stress.

• Dextrose: readily available energy source to help calves cope with the increased demand for energy used for cooling and immune function. 
• Betaine: acts as a protective osmolyte and holds water inside cells keeping calves hydrated and protected against water and electrlyte losses.
• L-glycine: building block for glutathione, one of the body's main antioxidant systems and play a role in managing inflammation. Helps to repair damage done to the gut during heat stress. 
• Electrolyte minerals: play an important role in carry water molecules directly into cells. 
• Yeast extract: improved gut health, immune function and metabolic balance. 
• Zinc Methionine: improve gut integrity and reduce oxidative stress.
• Yucca Schidigera: reduce oxidative stress and improved immune function. 

Final Thoughts

Calves don't have to be exposed to desert heat to show signs of heat stress.  Any temperature above the thermal neutral zone will increase energy and water demands, funneling nutrients away from growth. Utilizing management and feeding strategies to mitigate the effects of thermal stress may prove advantageous when comes to calf growth, health, welfare, and future production. 

We discussed some additives that can help the calf cope with thermal stress. Check out the calf distinction store for more about our electrolyte, Immu-lyte Black Label, formulated specifically with hydration in mind. And of course, our flagship product, Surveillance Calf, to keep your calves resilient through the long hot summer ahead. 

Written by: Mariah Gull, M.S. 

Sources: 

 Effect of birth season on Holstein calves’ voluntary water intake. Antenucci et al. U Bologna.

 Effects of heat stress on physiological indicators and weight gain in preweaning dairy heifer calves in a humid continental climate. Conrad et al. U Guelph.  

Plasma proteomic shifts from thermoneutral to heat stress conditions in preweaning Holstein heifers. Manriquez et al. CSU.