CA: Preparing for Summer Heat: Protecting your Employees and Cows

Dr. Michael Payne UC Davis, School of Veterinary Medicine & Director CDQAP

The weather is heating up and now is good time to ensure protections are in-place to prevent heat stress.

For Employees: An employee working in moderately warm weather can lose about 3/4 quart of water -- 1% of his body weight -- per hour. Heat stress may impact different employees differently depending on age, physical and medical conditions, exertion, acclimatization and water consumption.


All employees should be encouraged to drink water frequently, about one cup every 15 minutes. Managers should try to schedule hot jobs for the cooler part of the day. New employees should be acclimated to high heat conditions over about two weeks. For employees working in the sun- provide shade and scheduled breaks.

Signs of heat exhaustion start with fatigue, headache, dizziness and nausea and progress to confusion, slurred speech and fainting. Provide medical aid promptly; for serious cases the most effective emergency first aid treatment (while awaiting medical services) is continuously soaking the patient’s body with running water, such as from a hose. California employers are required to provide employee training on heat illness prevention and have a written plan.

Cal-OSHA’s heat illness prevention webpage provides considerable information including video links, pocket guides in English and Spanish and a calendar of training courses.


For Cows: Cows can also become stressed from the heat. Even at low humidity, production suffers when temps hit low 80s. Simple low-cost preparations for livestock that can be made now include making sure all water troughs are working and clean, this is particularly important for troughs at the exit from the milking parlor, where cows consume half their daily water intake.

In general shade is the most cost-effective heat-stress mitigation available, reducing heat load of cattle by 30 to 50%. The recommended shade area per adult cow is 40 to 50 square feet. You’ll also want to check nozzles on sprinklers/soakers and fans for proper function, volume output and direction. It takes roughly a quart of water to soak a cow’s back but water running onto the udder is wasted and can predispose her to mastitis.

Finally, be sure to sort cattle during cool morning hours and schedule vaccinations when temperatures drop. Detailed information on management of both routine and emergency heat stress prevention in dairy cattle can be found by linking to CDQAP’s heat stress page or by visiting CDQAP home page at and searching under animal care topics.