What is the difference between heat stress and heatstroke in animals?

Heat stress and heatstroke in animals: know the difference and act in time to prevent serious harm.

Heat stress and heat stroke are two different stages of the same threat: excessive heat load in animals. Heat stress is the early phase in which the body is still attempting to compensate, while heat stroke is a medical emergency in which body temperature rises so high that organs become damaged. The difference lies in the severity and the speed of intervention required. In this article, we answer the most frequently asked questions about heat stress and heat stroke in livestock and farm animals.

When does heat stress become dangerous for animals?

Heat stress becomes dangerous when an animal’s body temperature consistently rises above the normal threshold and the body can no longer efficiently dissipate heat. For most farm animals, this risk begins with a combination of high temperatures and high humidity, commonly referred to as the Temperature Humidity Index (THI).

In pigs, physiological stress begins at around 25 degrees Celsius, in poultry at 28 degrees, and in dairy cows at THI values above 68. When ambient temperatures remain high throughout the night, animals do not get sufficient recovery time. That is when heat stress becomes truly dangerous: the cumulative load builds up.

Factors that accelerate the danger of heat stress:

High humidity combined with heat
Poor ventilation in barns
Overcrowding in the barn
Insufficient access to fresh drinking water
Dark or poorly insulated barn walls that retain heat
Animals in a vulnerable phase such as pregnancy, lactation, or recovery from illness

At the cellular level, the body responds to heat load by losing water from cells, which disrupts osmotic balance. This is precisely why betaine as an osmolyte plays an important role in supporting animals in warm conditions.

What are the symptoms of heat stress in animals?

The symptoms of heat stress in animals include an increased respiratory rate, reduced feed intake, lethargy, and excessive panting or open-mouth breathing. These signs are the first warnings that an animal is struggling to regulate its body temperature.

The symptoms vary somewhat by species, but there are clear common characteristics:

In poultry, you will see open-mouth breathing, spread wings, reduced egg production, and in severe cases, mass mortality. Chicks actively seek out cooler spots and significantly reduce their movement.

In pigs, symptoms manifest as panting, reddening of the skin, reduced feed intake, and lying on cool floor areas. Pregnant sows are particularly vulnerable and may experience embryonic mortality.

In ruminants such as cattle, the main signs are an increased respiratory rate of more than 80 breaths per minute, salivation, declining milk production, and reduced rumination time.

In addition to these visible signs, there are also performance-related indicators that become apparent somewhat later: lower feed conversion, poorer carcass composition, and greater loss of uniformity within flocks. Intervening early based on the first behavioral signals prevents heat stress from escalating into a life-threatening situation.

How does heat stroke differ from heat stress?

The difference between heat stroke and heat stress is that heat stress is a physiological adaptive response in which the animal is still functioning, while heat stroke is an acute medical emergency in which the thermoregulatory system fails completely and organ damage occurs.

During heat stress, the body actively attempts to compensate: blood circulation to the skin increases, breathing speeds up, and feed intake decreases to produce less metabolic heat. The animal is stressed but is still in an active adaptation phase.

In heat stroke, that compensation is exhausted. Body temperature rises to critical levels, often above 41 to 42 degrees Celsius in farm animals. At that point, vital organs become damaged — the brain, the kidneys, and the gastrointestinal tract. The intestinal barrier loses its integrity, leading to the leakage of bacteria and endotoxins into the bloodstream. This can result in sepsis and death.

A practical distinction:

Heat stress: The animal is alert but panting, eating less, and seeking shade. Body temperature is elevated but not yet critical.
Severe heat stress: The animal is lethargic, has coordination problems, and shows extreme panting. Immediate intervention is required.
Heat stroke: The animal can no longer stand, loses consciousness, and has convulsions. A life-threatening emergency requiring immediate veterinary assistance.

The window between severe heat stress and heat stroke can be very short in poultry and pigs — sometimes a matter of hours. Rapid recognition of escalation is therefore essential.

Which animals are most at risk of heat stroke?

The animals most at risk of heat stroke are pigs, poultry, and high-producing dairy cows. This is because they have high metabolic heat production, limited ability to sweat or cool themselves, and are often kept at high stocking densities.

Pigs have no functional sweat glands and rely entirely on respiration to dissipate heat. This makes them particularly vulnerable. Sows in late pregnancy or early lactation face additional risk because their metabolism is already running at full capacity.

In poultry, the risk is high due to their rapid metabolic rate and high stocking densities in barns. Broilers in the finishing phase are especially susceptible because their body mass is relatively large and their heat production is at its peak.

In dairy cattle, high milk production generates enormous internal heat. Cows producing more than 30 liters per day generate so much metabolic heat that they can already enter a negative heat balance at moderate outdoor temperatures.

Other at-risk groups include young animals with a thermoregulatory system that is not yet fully developed, animals recovering from illness, and animals with a high genetic predisposition for rapid growth. The fast-growing genotypes that are economically attractive also turn out to be the most vulnerable under heat stress.

What should you do when an animal has heat stroke?

When an animal has heat stroke, you must act immediately: move the animal to a cool, well-ventilated environment, gradually cool the body with lukewarm water, and contact a veterinarian right away. Never use ice-cold water, as this can cause dangerous vasoconstriction.

The first few minutes are critical. Here is the correct order of action:

Move the animal immediately to shade or a cool barn with good air circulation.
Cool the animal gradually by spraying lukewarm to cool water over the neck, armpits, and legs. Do not start with the entire body at once.
Provide ventilation using fans to enhance evaporative cooling.
Offer drinking water if the animal is still able to drink. Add electrolytes if possible to support osmotic balance.
Call a veterinarian immediately. In the case of heat stroke, veterinary treatment is necessary, even if the animal appears to be recovering.
Monitor the animal for signs of shock, convulsions, or loss of consciousness.

What you should absolutely not do: submerge the animal in cold water, leave the animal lying on a warm floor, or delay intervention because the animal “still looks reasonably okay.” Heat stroke can be rapidly fatal, and organ damage can continue even after the animal has been cooled down.

How do you prevent heat stress and heat stroke in livestock?

Heat stress and heat stroke in livestock can be prevented through a combination of barn management, water supply, nutritional strategy, and targeted supplementation. Prevention is always more effective than intervening after the fact, especially since productivity losses due to heat stress also accumulate during periods with no visible symptoms.

In terms of barn management, the most important measures are:

Ensure adequate ventilation and air circulation in the barn
Install misting systems or cooling fans during high temperatures
Adjust feeding times: provide feed in the early morning and late evening
Ensure continuous access to fresh, cool drinking water
Temporarily reduce stocking density during extreme heat
Insulate roofs and walls to limit heat absorption

At the nutritional level, it is advisable to adjust the energy density of the ration and reduce protein content to limit metabolic heat production. Electrolyte supplementation via drinking water helps support osmotic balance, which reduces the cellular stress response.

Prevention also starts with monitoring. Track THI values and intervene before symptoms become visible. Most production losses due to heat stress have already occurred by the time a farmer notices the first clear behavioral signals.

How Jodoco helps with heat stress in animals

At Jodoco, we develop scientifically substantiated products that support animals during heat stress, both preventively and during periods of acute heat load. Our approach is based on the action of natural betaine as an osmolyte: betaine helps cells retain moisture, reduces epithelial stress, and protects the intestinal barrier — precisely the mechanisms that come under pressure during heat stress.

What our products specifically do during heat stress:

Osmoregulation: Betaine helps cells maintain their fluid balance, limiting cellular damage caused by heat
Intestinal barrier protection: Betaine strengthens tight junction proteins and prevents the intestinal wall from leaking during heat stress
Maintaining technical performance: Studies show that betaine supplementation during heat stress improves breast muscle weight, body weight gain, and feed efficiency in poultry
Reproductive support: In sows during warm periods, betaine helps reduce embryonic mortality and increase the number of live-born piglets
Electrolyte balance: Our drinking water products support osmotic balance and are easy and flexible to dose through the drinking water system

Our products such as Jodoplume are specifically developed for application via drinking water during heat or coccidiosis stress, while Jodobet as a feed additive provides structural support for osmoregulation and methyl donor function. Want to learn more about our drinking water and feed additives for animals, or curious about which solution best fits your situation? Contact us and we will be happy to think it through with you.