07/07/2025
HEAT STOKE AND HEAT STRESS
Heat stress causes heat stroke. When the heat index reaches over 105 animals and people it can cause exhaustion, cramps, heat and sunstroke. If the air temperature is 85 degrees and the humidity is 80%, the heat index will be 99. Raising the air temperature 10 degrees F. will result in the heat index climbing to 113. A heat index over 130 is a very dangerous situation. In a closed car with an outside temperature of 72 degrees F, the temperature inside can rise 40 degrees F higher within an hour.
Pigs and dogs are very sensitive to heat because they do not sweat as much as other animals. Livestock in areas where heat stroke is possible should always have access to water and shelter from the sun. Dogs which have reduced nasal airway capacity, medically called brachycelphalic (i.e. bulldog type breeds), hypothyroid dogs, obese and older patients have more problems tolerating the heat. The brachycephalic airway obstructive syndrome is more common in the English bulldogs, pugs and Boston terriers; these dogs have stenotic nares, elongated soft palates, everted laryngeal saccules and/or everted tonsils. Should you ever take the temperature of an animal, and it is over 106 degrees then first start pouring water on this patient, before calling the veterinarian. Any patient with a temperature of 107 degrees should have alcohol sprayed or lightly poured over their body, if possible; this is the magic temperature that heat stroke is starting to occur, damage to tissues can possibly occur and medical treatment is needed. Alcohol evaporates much quicker and removes heat faster than water. Once you have run out of isopropyl alcohol, or even ethyl alcohol over 40 proof (i.e. vodka), then start using water. Cool down a hot animal until they are 103 degrees F re**al temperature, and then reduce the amount of water or alcohol rinses in order to not drop the body's temperature to below normal. If one cools down an animal too quickly and to a below normal temperature you may cause the patient to go into shock and thus we do not recommend ice water baths. Ice and ice packs are ok if you do not have any water available. After the initial wetting down/alcohol application use the air conditioner in the car on your wat to taking the patient into the veterinarian. We realize that water is usually quicker to find and start using than to wait until someone can run to the nearest store for rubbing alcohol. It should be noted that sheep and goats can normally have a temperature of 104 degrees during the day in summer, and birds can normally have a re**al temperature of 103-108 degrees. Birds and any other animals should be misted with a spray of water if they are showing signs of heat, such as spread out wings in a bird. Cattle that have been on fescue grass can easily develop heat stroke, due to a mold causing the body to not regulate its temperature very well. There are many other causes for a patient to have a high temperature, which can range from systemic infections to toxins to other poisonings affecting the body. We recommend blood tests with heat stroke patients for many reasons. Hypoglycemia, seizures, malignant hyperthermia, exercise induced collapse and other underlying problems can present as a recumbent patient with hyperthermia, especially in hot weather. A dog with malignant hyperthermia is rigid, while an exercise induced collapse in Labrador retrievers will have a flaccid muscle, and yet a similar Collie Collapse disorder has all 4 legs as stiffness. In livestock there are other medical conditions to consider such as anhidrosis in horses to fescue grass issues with cattle.
If any animal is in the hot weather, appears to have rigid muscles, an increased respiratory rate, salivation, an outstretched neck and/or weakness you should make an attempt to reduce the core temperature of the animal until veterinary care can arrive and/or you can transport. If under 104 degrees F. the animal should be placed in the shade and watered down. Giving too much water to drink at once can cause problems, especially in pigs. If the body temperature is greater than 105 degrees, a call to the veterinarian is indicated. Animals with a body temperature of 106 degrees Fahrenheit or greater should be examined as they can have a total body break down called disseminated intravascular coagulation occur later on. Disseminated Intravascular Coagulation (DIC) can then cause a brain problem; many strokes and shock can usually be prevented with an exam, tests and medicines before the collapse occurs. If the clotting factors are low and/or if the animal has had a serve hyperthermia there is an IV treatment with plasma which is indicated if available. With initial treatment some animals may even require a cold water e***a, while other species such as horses and pigs we do not give routinely give e***as to.
IV fluids and medicines are usually needed for animals that have a temperature over 106-107 and appear distressed; each species is treated differently. If in doubt with small animals we will recommend hospitalization, blood tests and IV fluids to prevent kidney problems and DIC from occurring. In many species from birds to pigs if there is dehydration then a hypernataremia (salt toxicity) can occur, along with a secondary acidosis and other problems. There are other causes for hyperthermia for which we have a handout for. Heat stroke and dehydration have similar signs as water toxicity which is seen mostly in humans and a low sodium level is seen on blood tests.
A pulse rate over 65 indicates a problem if horses are undergoing possible heat stress. Rectally take the temperature of all animals if you feel they may be sick and/or hot. Because of the design of an animal’s ear, the ear thermometers are not as accurate (but better than nothing if you do not have any re**al or oral thermometer to use re**ally). Shock, intestinal shut down, muscle weakness and other signs indicate a possible heat stroke. Once the animal has been watered down then call the veterinarian, as there are drugs which may be indicated.
If the heat index is over 120 your horse should be cooled down if he appears hot. When watering a horse wipe the water off your horse if possible, as this is more effective than just spraying the horse. A small amount of water left against the skin can cause the cooler water to run off the patient before the water can cool him down; this minor loss of efficiency is probably only important in a down animal. Ensure you do not develop heat stroke by going out and preventatively treating your horse if he looks okay. A horse in the summer can easily require 5-6 gallons of water a day, and he needs at least this much more if he is undergoing only a few hours of endurance. Endurance horses should also be provided electrolytes when undergoing trials; the average horse with a brown mineral salt block available does not need daily electrolytes when on pasture or in the barn. In our area we recommend fans and/or the portable misting fans (swamp coolers) if possible, in hot barns on extremely hot days. Any horse that has anhidrosis, or inability to sweat, should be tested for a low thyroid condition.
Dehydration and heat stroke/heat stress go hand in hand. Compared to 70 degrees F livestock will required 2.5x the amount of water at 95 degrees F. Always ensure water is adequate and present twice a day in very hot weather. Stressed and high strung animals do not tolerate heat stress very easily. A good vaccination program, parasite and fly control programs helps to reduce the stress and animal loss during hot weather.
If an animal has been without water you need to SLOWLY rehydrate them, especially if it is a pig. For a pig you give a cup of water per 100 # every 30 minutes or so, as they are very, very sensitive to water deprivation and the concerns if rehydrated too quickly. For a 1000 # livestock this can be a gallon every 1/2 hour. Rehydrating an animal too quickly can cause seizures and death. Within 6 hours the animals should be rehydrated and more can be added at a time for pigs and after 10 gallons in adult livestock they can have water ad lib. We have a separate handout on this “salt toxicity” (lack of water) in pigs.
To help reduce heat stress one should provide shade or shelter if possible. Water sprinklers may help those livestock in confinement; especially with night sprinkling. If you feed less than 1/3 of the ration early in the morning, and 2/3+ near dark this can also help reduce activity during the heat of the day for livestock in confinement; feeding before night also helps reduce internal fermentation heat products within the herbivore's body during the daytime. Switching from a dark colored bedding to a lighter colored bedding or straw also helps somewhat. For non-milking adult livestock and horses feeding only once at night time is adequate. Always have adequate water available, especially if the animal is outside in hot weather. If you have a pig that has been without water for more than a couple hours, only provide a small amount of water (1 to 2 cups/100 # every 30+ minutes to 1 hour) to avoid salt toxicity and seizures. Fans do help to keep animal from overheating by evaporation of any sweat on the patient. A ceiling fan should blow down in the summer (up in the winter if in a closed room). We have more information on large fans, dairy barns, feedlots, etc.. For the range cattle heat shades need to be durable if on pasture (i.e. StrobelShades.com). A Quonset type hut can be used for summer and winter if adequate air flow in the summer, yet plastic and fabric will not hold up. Dairy barn-like awnings are also cost effective in some areas for shade and rain. There are no great products that are portable and will last for shade and to prevent heat stress.
If you are out for a walk and you yourself cannot hold your hand onto the asphalt or pavement for 5 seconds without it being too hot, then you probably should not be walking your dog at this time. Instead of boots consider instead waiting until it is cooler. Blowing a fan over a bowl of water towards a dog can help somewhat and if an evaporative cooler is used 5-15 degrees F the temperature can be reduced.
When one drives with their pet in a car, and the pet is not restrained, on a hot day it is tempting to have the windows down. Even if only the driver’s side is down we see many dogs that jump out of the open window anytime to go chase a squirrel they see, etc. It is true that if the car is sitting you especially want to crack the window, but as with driving not enough to allow an escape. When driving keep the windows up if the pet is not restrained.
www.NelsonRoadVet.com
Veterinarian Longmont, Colorado | Small and large animals | Dogs, cats, livestock, exotics | Preventative care, dentistry, surgery, acupuncture, ultrasound, in-house laboratory, pharmacy, farm calls, pet boarding.
