The phrase “sweating like a pig” can conjure up mental images of streams of sweat pouring down pigskin on a sweltering day, but it’s one of the most misleading idioms in the English language. Pigs have only a limited number of functioning sweat glands, so they sweat very little, and the small amount of sweat they produce doesn’t have much of an impact on their body temperature. So, how pigs cooling down?
Pigs are endothermic, or warm-blooded, meaning they maintain a stable body temperature regardless of the temperature of their environment. In most cases, the body temperature of endothermic animals is warmer than that of their environment. Conversely, ectotherms, or cold-blooded animals, depend primarily on external heat sources, so their body temperature changes along with the temperature of their surroundings.
There are two ways animals regulate their body temperature: metabolism and behavior. The main difference between the two types of thermoregulation is that one is fast and the other takes a long time.
“The metabolic approach to thermoregulation is really quite slow,” said Dan Tucker, professor of public veterinary medicine at the University of Cambridge in the UK metabolism, or the process by which the body converts ingested calories into energy. Metabolic cycles, in turn, generate heat. A 2006 article published in the magazine Physiological overviews (opens in new tab) has shown that when pigs are exposed to constant hot or cold temperatures for days or weeks, these cycles can be turned on or off by thyroxine to generate extra heat or cool the body.
Related: Which animals sing?
Behavioral thermoregulation, on the other hand, can help cool or raise body temperature in a much shorter period of time. In hot weather, pigs wallow in water or mud, which affects body temperature much like human sweat, Tucker told Live Science. As the water or mud evaporates from the pig’s body, it cools the animal down. Pigs can also seek out shady areas or “move heat away from their bodies by lying flat on a cool surface,” Tucker said. Pigs also pant to cool off. Panting increases airflow and evaporation of water from the lungs, releasing extra heat from their bodies.
However, many groups within the broader pig family live in “more temperate parts of the world, where they expend more energy keeping warm than cooling off,” Tucker said. In cold weather, pigs will huddle together for warmth, build nests, or shiver—a behavior commonly seen in piglets just hours after they are born.
When pigs are exposed to higher temperatures, they reduce their feed intake. This is another method of cooling down because digesting less food reduces the amount of heat generated during foraging, eating, and digestion, Tucker said. In fact, a pig’s body size is an important factor in its thermoregulation: Small pigs lose more heat through their skin than large pigs, which “have a smaller surface area to body volume ratio and therefore a smaller surface area for heat release,” Tucker noted. As a result, farmers who breed pigs specifically for rapid growth and more efficient meat production will experience more heat stress in their herds as the pigs are larger.
Given that exposure to hot environments can cause pigs to eat less, which in turn can result in smaller pigs, pig farmers should be concerned about the impact climate change when global average temperatures rise? Finally, according to a study published in the journal, heat stress can lead to reduced sperm quality in boars, smaller litter sizes and the inability to conceive in sows Acta Veterinaria Scandinavica (opens in new tab). Prolonged exposure to hot temperatures can weaken pigs’ immune systems, and at higher extremes, pigs can go into hyperthermic shock – which is actually cardiovascular collapse. Her blood pressure Drops that can cause unconsciousness and even death.
“Pork is the second most consumed meat in the world after chicken,” Tucker said. Farmers need to consider the increasing likelihood of heat stress, not only for the value of their herds, but also as an animal welfare issue, Tucker added.
So where does the expression “sweat like a pig” come from? The expression comes from the process of melting iron. When hot iron is poured onto sand, the cooling pieces resemble a sow and piglets, he reports McGill Office of Science and Society (opens in new tab). When the surrounding air reaches its dew point, beads of moisture form on the surface of the metal, and this sweating indicates that the “pig iron” is cool enough to the touch.
This article was originally published on Live Science on September 9, 2012 and updated on June 13, 2022.
https://www.livescience.com/32118-do-pigs-sweat.html Do pigs sweat? | Live Science