Heat stress is an important cause of poor health in animals and every animal experiences it differently. Even people experience heat stress, though we’re better equipped to deal with it than some animals. Understanding what causes heat stress and how to prevent it are an important part of raising and looking after any animal. But more importantly, if you’re not able to prevent heat stress, it’s crucial to understand the signs and symptoms of heat stress in your animals so you can get them the treatment they need as soon as possible. 

There are several signs to look out for associated with heat stress in animals. These can include difficulty or heavy breathing, excessive panting, anxious behaviour, excessive water consumption, weakness, and even vomiting or diarrhoea. If you suspect heat stress in your animal and they are showing any of these signs, get them the care they need immediately. 

A lot of animals will express similar symptoms and behaviours when succumbing to heat stress which are telltale signs. But just as we all celebrate our profound differences in each other, animals also have their own unique characteristics which can make heat stress appear differently. For example, a sheep may react quite differently than a horse when it encounters heat stress and knowing what to look out for and how to prevent it could even mean the difference between life and death.

What Will Animals Do During Heat Stress

High temperatures and extreme humidity can cause unnecessary suffering for your animals. During times of extreme weather, it’s important to monitor your animals to ensure they stay cool, healthy, and safe.

Keep a lookout for signs that your animal may be overheating; they may:

  • Exhibit excessive panting
  • Drool excessively 
  • Breath with difficulty
  • Drink a lot of water
  • Behave anxiously such as acting agitated, refuse to lie down, or make more noise than usual
  • Show signs of weakness
  • Act incoherently
  • Collapse or start to seize
  • Have bright red gums
  • Vomit or have diarrhoea

Over longer periods of excessive heat, you may notice:

  • Reduced weight gain
  • Increased instances of infection
  • Lower fertility, increased embryo mortality and birth defects
  • Emaciation

Climatic Factors for Heat Stress in Animals

Heat stress in animals can be caused by a variety of climatic factors such as: 

Ambient body temperature – Air temperatures above an animal’s body temperature will limit their ability to lose heat through convective cooling.

Relative humidity – Increased humidity reduces an animal’s ability to lose heat through evaporation by panting or sweating.

Solar radiation – Heat produced by solar radiation can significantly exceed the metabolic heat produced by an animal.

Wind speed – In calmer air conditions heat stress is likely to increase due to dramatically decreased convective heat loss.

Night temperatures – high night temperatures prevent the loss of heat that is gained during the day.

Heat Stress in Sheep

Heat stress in sheep can be affected by factors influenced by their:

Fleece – Sheep fleece not only protects against the cold, it regulates their temperature in the heat as well. Shorter wool increases the radiant energy passing through to the skin.

Breed – Sheep breeds from cooler regions are more susceptible to heat stress. These breeds usually have compact bodies, short legs and necks and smaller ears to help maintain body heat.

Age – Lambs have a high metabolic heat production, a higher respiration rate, a large surface area relative to their mass and limited fleece length therefore are more susceptible to heat stress.

Pregnancy – Ewes in late gestation have an increased metabolic heat production and are therefore more susceptible to heat stress.

Signs of Heat Stress in Sheep

A relatively simple visual sign that sheep are becoming heat stressed is changes in their breathing. This is because 65% of heat loss in sheep occurs through panting. The level of panting (and therefore the level of heat stress) you observe could range from:

Mild – closed mouth and rapid chest movements

Moderate – fast panting with mouth open and rapid chest movement

Severe – rapid open mouth panting, extended neck, head facing up and tongue extended

Extreme – open mouth with tongue fully extended, head lowered, deeper breathing and reduction in panting for short periods.

Behaviour in heat stressed sheep 

Another visual aspect to observe is changes in sheep behaviour, they will adapt their behaviour to maximise heat loss in circumstances of overheating and you can use this method alongside their level of panting to determine the impact of heat on the animals.

Behaviours you may observe in sheep that are heat stressed include:

  • Seeking shade
  • Standing for longer than normal periods
  • Crowding around water troughs 
  • Drinking a lot of water
  • Eating less dry matter
  • Bunching together to seek shade from other animals
  • Increased respiratory rate
  • Immobility or staggering

Heat Stress in Pigs

Pigs are homeothermic animals meaning they act in certain ways to regulate their body temperature. Heat stress in pigs can be affected by factors influenced by their: 

Anhidrosis – As with all poultry species pigs are not able to sweat efficiently enough to cool off which makes them acutely sensitive to heat stress. 

Age – Whereas young pigs are very sensitive to the cold, older pigs and especially sows are more sensitive to the heat.

Weight – Pigs carrying a lot of weight, over 75kg are more susceptible to heat stress.

Pen conditions – The density of their living arrangements, the type of building and the air flow can all contribute to inability to regulate temperature.

Behaviours of Heat Stress in Pigs

It’s important to observe changes in pigs to watch out for signs of heat stress. Signs of heat stress in pigs include:

  • Open mouth breathing
  • Vocalisation
  • Blotchy skin
  • Stiffness
  • Muscle tremors
  • Reluctance to move
  • Decreased feed intake
  • Increased water consumption
  • Increased respiratory rate

Heat Stress in Horses

Exercise is integral to a horse’s health and there’s no better time to ride than in the summer but heat stress in horses can quickly become life threatening. Horses produce a large amount of heat, through digestion and muscular activity. Horses can easily rid themselves of excess heat in cooler climates through blood shunting to the skin but this technique is not enough if the air temperature is warmer than their blood. 

The horse is the only mammal, other than humans, that cools themselves primarily by sweating. Sweat makes the body wet to enable cooling through evaporation. This cooling system breaks down during extreme hot and humid weather when sweat is unable to evaporate. This can lead to heat exhaustion or even heat stroke. 

Signs of Heat Stress in Horses

Signs to observe during heat stress in horses include:

  • Profuse sweating or less sweat than is expected
  • Hot skin (this may progress to cold if the skin circulation shuts down)
  • Muscle weakness
  • Stumbling
  • Rapid breathing
  • Rapid heart and pulse rates (that aren’t recovered after exercise)
  • Increased body temperature of over 38 degrees C
  • Signs of dehydration including loss of skin elasticity, sunken eyes, tacky membranes and cessation of urination.

Heat Stress in Chickens

Heat stress in chickens can be due to predisposed factors such as:

  • Genetics
  • Feather cover
  • Drinking water temperature and availability
  • Age – older hens, heavy breeds and broilers are more susceptible to heat stress.

Signs of Heat Stress in Chickens

Signs to observe during heat stress in chickens include:

  • Laboured breathing and panting
  • Pale combs or wattles
  • Lifting wings away from their body
  • Lethargy
  • Diarrhoea
  • Seizures or convulsions

If your chickens are exposed to heat stress for long periods you may notice changes in their growth rates, egg production and hatching rates.The egg quality may also be affected with symptoms such as smaller eggs, thinner shells and overall poor internal egg quality. 

Heat Stress in Goats

Some livestock tolerate heat better than others and sheep and goats tend to be less susceptible to heat stress than swine, cattle, equine, poultry, llamas and alpacas. Goats tend to tolerate heat better than sheep and more so goats with loose skin and floppy ears are likely to tolerate better than other goat species.

As with sheep, a goat may show signs of heat stress by:

  • Increased respiratory rates
  • Increased sweat
  • Open mouth panting
  • Suppressed feed intake

Small goats can withstand short periods of heat stress as long as these periods are followed by cooler temperatures such as during nighttime where their body temperatures are able to reconfigure. However, long periods of heat stress can affect performance, energy and mineral balances.

Preventing Heat Stress in Animals

Now that we have identified the signs and symptoms that your livestock may express in times of heat stress, it’s fundamental to remember that prevention is always better than a cure. Most incidences of heat stress in animals can be significantly reduced if there is preliminary management to prevent it. 

Maintain excellent herd health and ensure top performance from your cattle, swine, ruminants, poultry and equine by preventing heat stress which can lead to other complications in your livestock. During the hot and humid summer months keep the following approaches to your livestock and their environment in mind to prevent heat stress and even fatal heat stroke:

  • Ensure they have access to plenty of fresh, clean water 24/7. In hot summer months keep the water in a shady area and top up with cold water.
  • Avoid physical exercise during the hottest hours of the day, especially during the summer months.
  • Rain can cause a sharp rise in humidity, so keep in mind that rainy days also have their heat stress risk factors.
  • Install a SmartShelter with sufficient airflow to keep your animal’s temperature at optimal levels.
  • Animals kept outdoors must have adequate shade during the hottest months.
  • If animals are needed to work ensure they have long rest periods and plenty of rehydration.
  • Mastitis, milk fever or ketotic affected animals can be infused with electrolytes to prevent onset of heat stress or hypothermia.
  • Give your animals enough space to wander so they can find cool spots to rest.

Remember that heat stress can affect us all and is not limited to livestock. If you have working dogs, don’t forget to check up on them and never leave animals in a car unattended during the summer heat.

If you’re worried about your animals overheating, SmartShelters have purpose built solutions to keep your animals cool and healthy. Get in touch today to discuss a truly smart livestock shelter solution.