Pigs are highly sensitive to surrounding temperatures and have a limited ability to regulate their internal body heat. They rely heavily on their environment and care practices to stay comfortable. Understanding how temperature impacts pigs is important for their health and productivity.
Normal Body Temperature and Measurement
A healthy pig’s normal body temperature ranges from 101.5°F to 102.5°F (38.6°C to 39.2°C). Temperature can fluctuate throughout the day, often being slightly higher in the afternoon or evening.
Measuring a pig’s temperature is done using a rectal thermometer, either digital or mercury. The thermometer should be lubricated with petroleum jelly or a water-based lubricant and inserted about one inch into the rectum, tilting it slightly to touch the rectal wall. Hold it for about one minute for digital devices, or two minutes for mercury ones.
Impact of High Temperatures
Pigs are susceptible to heat stress because they have very few functional sweat glands, relying instead on methods like panting to dissipate heat. When temperatures rise above their comfort zone, around 70°F for older finishing pigs, sows, and boars, pigs can experience heat stress.
Signs of heat stress include panting, lethargy, reduced appetite, and reddening of the skin. Severe cases may show muscle tremors, stiffness, open-mouth breathing, vocalization, or collapse. Prolonged heat stress can lead to excessive water consumption, electrolyte loss, acid accumulation, diarrhea, or death.
High temperatures negatively affect a pig’s physiology, growth, and reproductive health. Growing pigs under heat stress show decreased feed intake, leading to reduced weight gain and feed efficiency as energy is diverted to maintaining body temperature. This can result in reduced muscle mass and increased fat deposition. For breeding pigs, heat stress can cause delayed puberty, decreased farrowing rates, smaller litter sizes, extended weaning-to-estrus intervals, and increased embryonic mortality or stillbirths.
Impact of Low Temperatures
Cold stress poses distinct challenges for pigs, particularly for piglets, which have minimal fat reserves and an underdeveloped ability to regulate their body temperature after birth. This makes them highly vulnerable to chilling within the first 48 hours of life. Even older pigs can experience cold stress if temperatures fall below their lower critical temperature, which varies by age, weight, and flooring type.
Signs of cold stress include huddling for warmth, shivering, and lying with their feet tucked beneath their bodies. If cold stress persists, pigs may develop long, rough hair coats, become thin, and exhibit poor growth. Diarrhea is also a common symptom.
Cold temperatures force pigs to expend more energy to maintain body heat, impacting their health and productivity. Pigs increase feed intake to generate more heat, but this energy is used for warmth rather than growth, leading to slower weight gain and reduced feed efficiency. This diversion of energy can compromise immune function, making them more susceptible to illnesses like scours, meningitis, joint infections, and respiratory problems. For neonatal piglets, chilling can increase pre-weaning mortality rates.
Managing Pig Temperatures
Maintaining optimal pig temperatures involves environmental controls, careful monitoring, and nutritional considerations. Proper ventilation year-round helps remove excess heat, moisture, and gases in warmer months and allows for dry air exchange in cooler periods without creating drafts. During hot weather, providing shade, increasing air movement with fans, and using misters or sprinklers can help pigs cool down through evaporative cooling. Allowing pigs to access wet concrete surfaces or mud wallows can also help dissipate heat.
In colder conditions, adequate bedding, such as straw or wood shavings, provides insulation and a warm area for pigs to burrow into, increasing their perceived temperature. Protecting housing from drafts, ensuring good insulation, and using heating lamps or heated mats, especially for piglets, help maintain warmth. Heat mats directly deliver localized warmth to piglets.
Access to fresh, cool water is important, as pigs increase water intake during heat stress. During cold weather, ensuring water does not freeze is also important to prevent dehydration. Nutritional adjustments can support temperature regulation; high-protein diets can increase metabolic heat production, and trace mineral supplementation can help pigs cope with stress. Regular monitoring of environmental temperature and pig behavior is important for timely adjustments and comfort.