Preventing Heat Stroke In Pigs: What Owners Should Know

Pigs are highly susceptible to heat stress and heat stroke, which can be fatal. Unlike humans, pigs do not have functional sweat glands, and their small lungs limit their ability to cool themselves by panting. As a result, pigs rely on external methods to regulate their body temperature, such as laying on cool surfaces, wallowing in mud, or taking dips in water. However, during hot weather, these methods may not be sufficient, and pigs can quickly overheat, leading to heat stroke. Heat stroke in pigs is characterised by increased respiratory rate, lethargy, reduced appetite, excessive water consumption, diarrhoea, and in severe cases, seizures and death.

Pigs' physiological limitations

Pigs are susceptible to heat stress and heat stroke due to several physiological limitations. Unlike most other animals, pigs do not sweat. Their sweat glands are largely dormant, and they rely on panting to maintain their normal body temperature, which falls between 101 and 103 degrees Fahrenheit. However, pigs have relatively small lungs, which limits their ability to cool down through panting.

Pigs' inability to sweat means they must rely on external methods to regulate their body temperature. They typically cool down by laying on cool surfaces, such as the ground or in mud holes, or by taking a dip in water. Their thick subcutaneous fat also makes it challenging for them to dissipate heat. As a result, pigs are prone to heat stress and heat stroke when exposed to high temperatures, especially in combination with high humidity.

During periods of heat stress, pigs exhibit increased respiration rates and a loss of appetite, which helps reduce internal heat production. If the heat stress persists, pigs may drink excessive amounts of water, leading to a loss of electrolytes and an accumulation of acids in the body, resulting in a loss of acid-base balance. This can eventually lead to diarrhoea or even death.

Additionally, pigs generate a significant amount of heat. A bacon pig, for example, produces heat equivalent to a 1KW bar heater. This means that confined buildings can become extremely hot, further exacerbating the risk of heat stroke.

How to identify heat stress in pigs

Pigs are more susceptible to heat stress than other animals due to their dormant sweat glands and small lungs. They are also prone to accumulating fat under the skin, which further increases their sensitivity to heat.

• Increased respiration rate and open-mouth breathing
• Loss of appetite
• Excessive drinking
• Increased urine output
• Diarrhea
• Vocalization
• Blotchy skin
• Stiffness
• Muscle tremors and weakness
• Reluctance to move
• Rectal temperature of 43°C
• Vomiting
• Bloody diarrhea
• Seizures
• Disorientation
• Drooling thick, rope-like saliva
• Glazed-over eyes
• Dry and crispy gums, tongue, and skin around the eyes
• Elevated body temperature
• Weakness, stumbling, or collapsing

If you observe any of these signs, it is important to take immediate action to cool down the pig and prevent further heat stress. Provide shade, access to cool water, and reduce their physical activity. If the condition is severe, seek veterinary assistance immediately.

Preventing heat stroke in pigs

Pigs are highly susceptible to heat stress and heat stroke due to their dormant sweat glands and small lungs. As a result, they are unable to cool themselves by sweating and rely on panting to maintain their normal body temperature. However, panting becomes ineffective at a certain point, and the pig's body temperature rises to dangerous levels, leading to heat stroke.

Provide Adequate Shade and Ventilation

Ensure pigs have access to shade, especially when outdoors. Provide at least 4 square feet of shade per pig for pigs up to 100 lbs. and 6 square feet of shade per pig for those weighing over 100 lbs. Additionally, proper ventilation and airflow are crucial. Regularly maintain and check cooling systems to ensure they are functioning optimally.

Maintain Water Access and Temperature

Pigs require continuous access to clean, cool water to regulate their body temperature. Keep drinking water temperature as low as possible, ideally around 10°C. Use ice or frozen tubs of water to lower the water temperature and reduce evaporation. Avoid feeding pigs during the hottest part of the day, typically between 10 am and 4 pm.

Implement Cooling Strategies

Use strategies such as misting fans, sprinkling cool water on the pigs, or providing wallows (mud baths) or kiddie pools with clean water to help pigs cool off. Ensure any cooling areas are also shaded to prevent the water from heating up.

Adjust Feeding and Bedding

Reduce protein intake during prolonged hot weather to decrease water requirements and lower the risk of dehydration. Additionally, minimize excess bedding, especially deep straw bedding, as it can act as a hotbed and increase lying temperatures.

Monitor for Early Signs of Heat Stress

Be vigilant for early warning signs of heat stress in pigs, such as increased respiratory rate, loss of appetite, lethargy, muscle tremors, and excessive water consumption. If pigs exhibit these signs, allow them to rest and provide cooling measures.

Take Extra Precautions for Breeding Animals

Overheating can interfere with the reproductive cycle of breeding animals. Provide extra cooling measures and closely monitor sows and boars for signs of heat stress, as they are particularly vulnerable.

Heat stroke treatment for pigs

Heat stroke is a dangerous condition that affects all pigs and can be fatal if not treated swiftly and effectively. As pigs do not sweat and have small lungs, they are prone to overheating in hot weather.

If you suspect that a pig is suffering from heat stroke, it is important to act quickly. Firstly, move the pig out of direct sunlight and into a cool, shaded area, or an air-conditioned room. Use a cool, wet towel on the pig's neck and back, changing it regularly to maintain a cooling effect. Do not use ice or freezing water as this can cause the pig to go into shock. You can also apply cool water to the pig's skin, as this will evaporate and remove heat. Once the pig has cooled down, take it to a vet as soon as possible to ensure it receives the necessary care.

While on the way to the vet, you can take additional measures to help cool the pig down and reduce its internal temperature. You can dribble cold water into the pig's rectum using a flutter valve, and you can also give the pig fluids to prevent dehydration. However, be careful not to give large amounts of water at once, as this can cause the pig to inhale the water, leading to further health complications. Instead, give small amounts of water at a time, or use an electrolyte rebalancing solution.

To prevent heat stroke in pigs, it is important to provide them with ample shade and fresh, clean water. Ensure they have access to wallows or mud baths, which can provide relief from the heat. Additionally, consider using a misting system or fans to help cool the air and increase ventilation.

Impact of heat stroke on pig reproduction

Pigs are highly susceptible to heat stress and heat stroke due to their inability to sweat and their relatively small lungs. Their thick subcutaneous fat also makes it difficult for them to regulate their body temperature. As a result, heat stress and heat stroke can have significant impacts on pig reproduction.

Firstly, heat stress can cause a reduction in milk production in lactating sows. This can lead to a decrease in the growth and survival of piglets, as they rely on their mother's milk for nutrition. Additionally, heat stress can interfere with the reproductive cycle of female pigs, delaying or suppressing the onset of oestrus, especially in gilts. This can result in a decrease in farrowing rates and an increase in the number of stillborn piglets.

Heat stress can also negatively affect male pigs, leading to lethargy, reduced libido, increased irritability and aggression, and degraded semen quality. This can decrease fertility and litter size.

In extreme cases, heat stroke can even cause the death of sows around farrowing, resulting in significant economic losses for pig farmers. For example, in one case study, a hot summer period led to a shortfall of approximately 200 piglets in a typical 500 sow breeder weaner unit over a four-week period.

To mitigate the impacts of heat stress and heat stroke on pig reproduction, it is essential to provide adequate cooling measures for pigs, such as shade, wallows, and access to cool water. Reducing stocking densities and providing proper ventilation can also help prevent heat stress in pigs.

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