Dog Discoveries

Nine Fascinating Facts About Dog Saliva

 

You likely don’t pay much attention to your dog’s saliva until you watch some droplets fall down, and then, before you know it, a little puddle of saliva has formed as your dog watches you eat a juicy steak. Dog saliva after all is meant to stay inside, nicely tucked inside your dog’s mouth, but in some breeds with heavy jowls, that can be easier said that done. Owners of such dogs seem to always be prepared for the saliva downpour and keep a towel handy so to catch those droplets and slingers. Dog saliva after all, may seem like something boring, but instead there are several fascinating facts about dog saliva that are worthy of discovering.

Pavlov Studied Dog Saliva….

Ivan Pavlov was a Russian physiologist who, after reading Charles Darwin, abandoned his religious career to totally dedicate himself to natural science. He therefore started studying the mechanisms underlying the digestive system in mammals.

As he researched the interaction between salivation and the action of the stomach, Pavlov decided to involve dogs in his studies. To better understand the mechanism, a clear tube was connected to the dog’s salivary gland in the cheek which allowed him to keep track of the amount of saliva collecting. Saliva production was therefore copious when the scientists placed food in the dog’s mouth.



Pavlov’s studies revealed that the biological production of saliva had an important function in the digestive process and that, without salivation, the stomach failed to get the necessary input to start the digestive process. This was proof that digestive functions were linked by biological reflexes in the autonomic nervous system.

When He Stumbled on an Interesting Phenomenon.

At some point, in the midst of observing dogs salivating when food was offered to them, Pavlov saw an interesting phenomenon unveil. He noticed that even when there was no food in sight, the dogs were still salivating. This happening at first was perceived as an annoyance considering that the tubes kept collecting saliva even when the scientists weren’t conducting research.

However, Pavlov carefully evaluated the situation and came to a possible conclusion that the dogs were likely drooling at the mere sight of the scientists’ white lab coats in anticipation for the food.

To prove this theory, he starting ringing a metronome to signal the approach of food. After several trials, he noticed that the dogs not only began to salivate upon hearing the noise of the metronome, but at some point even when no food was present!

This led to the discovery that salivation, a biological reflexwas capable of being modified by something psychological, in this case, a sense of anticipation. Pavlov named this type of reflex a “conditioned reflex,basically a reflex that resulted from associative learning so to differentiate it from the biological reflex, while the whole process of associative learning was called Pavlovian conditioning in his honor, today also known as respondent conditioning or classical conditioning.

This discovery opened the doors to understanding the science of behavior and American psychologist John Watson further expanded this research and, with his Little Albert studies, used its principles to change a human’s behavior.

Dog Saliva Can Help Clean Wounds….

When you get a wound you likely rush to wash it with soap and water, but what does a dog have to do? Prior to domestication, that means prior to when dogs had owners rushing to clean and disinfect a dog’s wounds, dogs relied on themselves to clean up a wound.

The mechanical action of a dog’s tongue along with saliva, helped remove any dirt or debris present on the wound’s surface. So yes, a dog’s saliva along with some tongue action can help remove stuff from the wound that shouldn’t be there, which is good.

The next question though is: does dog saliva have any antibacterial properties?

You may have stumbled at some point or another on somebody claiming that it’s good to let dogs lick their wounds because dog saliva has healing properties. This statement makes sense overall considering how quickly wounds in the mouth tend to heal, but is there any truth to it?

To attain the answer to this we had to go dig up some studies. According to a study conducted by Benjamin L. Hart, and Karen L. Powell, saliva in male and female dogs was found to have antibacterial properties, in particular against Escherichia coli and Streptococcus canis, which comes handy when mother dogs are licking their newborn pups which are predisposed to highly fatal coliform enteritis and septicemia. This suggests that wound licking in dogs may therefore help reduce contamination with E. coli and S. canis

But Only Up to a Certain Point.

As with everything in life, moderation is key. Sure, dog saliva may have antibacterial properties, but it also contains bad bacteria as well.

Also, given the opportunity, dogs will tend to lick a whole lot which can cause loads of trouble as the repeated abrasive action of the tongue, along with keeping a wound moist for too long (moisture attracts bacteria), may lead to an infection or injury. 

This is why veterinarians often recommend that dogs wear the infamous “cone of shame” AKA the infamous  Elizabethan Collar

“When a pet licks a surgical incision, he is introducing contamination, not removing it. In the case of non-surgical wounds, I don’t care if a pet licks a few times before treatment is initiated, but once the area has been thoroughly cleaned and medications started, the downsides of licking once again outweigh its benefits.”~Dr. Jennifer Coates

Did you know? When dogs lick their paws in excess, they may cause what is known as lick granuloma, as seen in the picture.

 

Saliva Aids in Digestion…

If your dog produces saliva, you must thank his salivary glands which are found in your dog’s upper and lower jaw. Want to know more about them? Dogs have two zygomatic glands by the cheek bone near the dog’s eyes, two parotid glands where the head meets the neck, two sublingual glands under the dog’s tongue and two mandibular glands, by the dog’s lower jaw.

As in humans, saliva helps keep Rover’s mouth nice and moist and helps lubricate the passage of  chewed-up food from the mouth through the esophagus and then all the way down to the dog’s stomach.  The blob of chewed-up food is formally known as “bolus” and the more slippery it is, the easier it will slide down without causing damage.

You might have heard the saying “the digestive process starts in the mouth” meaning that chewing stimulates the process of breaking down some components of food so that they’re more easy to assimilate. Well, this mostly applies to humans who express amylase in saliva so to break down starch in the mouth. In dogs, amylase is expressed only in the pancreas (Axelesson et al, 2013) .

According to Dukes’ Physiology of Domestic Animals, saliva may vary from a watery consistency to thicker, mucoid-like. For instance, the parotid glands, produce a watery saliva, while the sublingual glands, on the other hand, produce a mucus-type of saliva rich in mucin, which helps the bolus travel from the mouth to the stomach.

But Excess Saliva May Be A Sign Your Dog is Nauseous.

Excess salivation should send you on a “barf alert.” Keep those paper towels handy and send Rover on a tiled area for an easy clean-up the moment you notice him drooling and smacking his lips. Why do dogs drool though when they are getting sick?

If dogs drool in anticipation of food and saliva helps kick start the digestive process, then why in the world is saliva again getting in the way when a dog is actually about to lose his lunch?

Well, here’s a fascinating fact: saliva in this case assumes a protective role. Since vomit is very acidic in nature, the increase in saliva seen when one becomes nauseous is meant to help minimize erosion to the mouth and tooth enamel caused by those potent gastric acids.

Did you know? Your dog’s salivary glands also increase salivation when there are irritating substances in the mouth.

 

Saliva Can Help Dogs Cool Down…

Dogs do not cool down primarily through their skin like humans do, but their main way of cooling off is by panting. You might not know this, but your dog’s saliva can play a role in helping Rover cool down when those temperatures soar in the dog days of summer or after exercising.

Here’s a little insight into the process. When your dog is hot, he will keep his mouth open and breath quickly. This heavy panting allows the saliva-moistened surfaces of his mouth and tongue to cool down by increasing evaporation. Since blood flows through the mouth and tongue, once the blood cools down, it reaches the rest of the dog’s body and thus, lowers the dog’s core temperature. This evaporation is ultimately one of the several ways dogs cool down when they’re hot.

But It Can Also Lead to Unsightly Stains

If you own a white colored dog with a passion for licking, you might be aware of the effects of excess licking on your dog’s coat, but what causes those stains in your dog’s fur in the first place? In this case, you must blame your dog’s saliva. According to Muller and Kirk’s Small Animal Dermatology the main cause for dog saliva and dog tears to cause unsightly reddish stains is due to presence of porphyrins. What exactly are porphyrins? Porphyrins  are simply molecules that contain iron as the result of the natural breakdown of red blood cells. While most poryphyrins are excreted from the body when a dog eliminates, traces of porphyrin may also be excreted through a dog’s tears, saliva, and urine.

And Finally Some Dogs Just Can’t Keep Saliva Indog saliva facts

Saliva is really supposed to be stored nicely in a dog’s mouth, some breeds though are by design naturally born droolers. The  shape of a dog’s upper lip (flews) can surely play a role in how predisposed a dog may be to drooling.

Many owners of dogs with particularly developed flews have gotten used to cleaning up what are known as “slingers;” basically, strings of drool that attach to floors, ceilings and walls every time slobbery dogs happen to shake their heads.

It’s very difficult to come by a Saint Bernard with a dry mouth. Many seasoned dog owners though have simply learned to cope with the drooling issue.

“You just always carry a towel and learn to live with it,” explains a fancier to the American Kennel Club Gazette. Coping mechanisms aside, those slingers are not to be underestimated: Barbara Meyer explains in her blog that, left alone, this spittle has the tendency to dry into a rock-like hardness and that she heard a dog owner speculating that it might be of interest to NASA for the purpose of gluing down the tiles of their space shuttles! Quite some amazing stories for just a spit of saliva, aren’t they?

Did you know? A 20 kilogram dog (around 44 pounds) is capable of producing  anywhere between a half a liter up to 1 liter of saliva a day! The amount is usually higher in dogs who are fed dry foods.

 

References:

  • Public Broadcasting Service (PBS), People and Discoveries, Ivan Pavlov, retrieved from the web on December 30th, 2016
  • Antibacterial properties of saliva: Role in maternal periparturient grooming and in licking wounds Benjamin L. Hart, Karen L. Powell, Physiology & Behavior Volume 48, Issue 3, September 1990, Pages 383–386
  • Lussi A, Jaeggi T. Erosion – diagnosis and risk factors. Clin Oral Investig. 2008;12:S5–13.

Photo Credits:

  • Wikipedia, Ivan Pavlov, Public Domain
  • Wikipedia, A statue of Ivan Pavlov and one of his dogs Илья Го. (грохотайло) – Я автор этой фотографии CCBY3.0
  • Flickr Creative Commons, osseousOctober 7, 2013, Luna licking CCBY2.0
  • Wikipedia, Canine lick granuloma / acral lick dermatitis; self-inflicted as an obsessive-compulsive self-destructive behavior,selfOwn work CC BY-SA 3.0
  • Flickr, Creative Commons, Paul Joseph, drool dog CCBY2.0


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