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8-6-2019
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Love, Actually: How a Tiny Peptide Drives Your Passion for Dogs
Oxytocin. Most of us think of it as the hormone that helps bitches whelp and produce milk. And yes, it’s that, but so much more. A series of recent studies have revealed how oxytocin has a major effect on the brains of both people and dogs to strengthen the human-canine bond – that indescribable interspecies attachment that might just explain why you’re reading this.
Oxytocin is a peptide hormone that is secreted into the blood from the pituitary, a pea-sized structure at the base of the brain, although it also can be made in many other cells of the body. Its size – just 9 amino acids long – truly belies its important role in how people and dogs respond to the world around them.
Oxytocin plays an important role in human communication. When a mother gazes at her infant, attachment begins to develop. You may be familiar with imprinting, in which an orphan baby duck becomes attached to a human and begin to follow it around. Human attachment is a more sophisticated version of this phenomenon, and is the basis of interpersonal relationships.
Oxytocin plays other roles in humans as well – it’s called the “love hormone” for a reason. Oxytocin makes you feel good when you’re with someone you love by stimulating the reward center in your brain, and it also reduces stress (1, 2).
Recently scientists have been studying the role of oxytocin in the human-canine bond. It was already known that interactions between humans and dogs resulted in oxytocin release into the blood stream of both species (3). To understand more about the mechanism of this mutual hormonal response, researchers performed experiments to ask the following questions: Is gaze important for mutual oxytocin release between humans and dogs like it is for mothers and infants? And does mutual oxytocin release happen between humans and hand-raised wolves or just with dogs?
To answer these questions, researchers measured urine oxytocin levels in dogs or hand-raised wolves and their people before and after spending 30 minutes alone in a room together (4). During that time, the owners could gaze at the dogs or wolves, talk to them and touch them.
Results: Dogs differed in the amount of time that they would gaze at their owners; they were divided into long gazers and short gazers. Long gazers induced significantly higher mutual oxytocin levels in both the people and themselves during the 30-minute interaction, whereas short gazers and wolves did not.
Conclusion: As in the relationship between mother and child, humans interacting with dogs experience gaze-induced mutual oxytocin secretion and the longer the gaze, the higher the resulting oxytocin levels in both humans and dogs (and the better both feel). This hormonal interaction is called the oxytocin-gaze positive loop (we’ll refer to it as the OGPL for short). This diagram illustrates that steps that are involved in this positive feedback loop:
Oxytocin is a peptide hormone that is secreted into the blood from the pituitary, a pea-sized structure at the base of the brain, although it also can be made in many other cells of the body. Its size – just 9 amino acids long – truly belies its important role in how people and dogs respond to the world around them.
Oxytocin plays an important role in human communication. When a mother gazes at her infant, attachment begins to develop. You may be familiar with imprinting, in which an orphan baby duck becomes attached to a human and begin to follow it around. Human attachment is a more sophisticated version of this phenomenon, and is the basis of interpersonal relationships.
Oxytocin plays other roles in humans as well – it’s called the “love hormone” for a reason. Oxytocin makes you feel good when you’re with someone you love by stimulating the reward center in your brain, and it also reduces stress (1, 2).
Recently scientists have been studying the role of oxytocin in the human-canine bond. It was already known that interactions between humans and dogs resulted in oxytocin release into the blood stream of both species (3). To understand more about the mechanism of this mutual hormonal response, researchers performed experiments to ask the following questions: Is gaze important for mutual oxytocin release between humans and dogs like it is for mothers and infants? And does mutual oxytocin release happen between humans and hand-raised wolves or just with dogs?
To answer these questions, researchers measured urine oxytocin levels in dogs or hand-raised wolves and their people before and after spending 30 minutes alone in a room together (4). During that time, the owners could gaze at the dogs or wolves, talk to them and touch them.
Results: Dogs differed in the amount of time that they would gaze at their owners; they were divided into long gazers and short gazers. Long gazers induced significantly higher mutual oxytocin levels in both the people and themselves during the 30-minute interaction, whereas short gazers and wolves did not.
Conclusion: As in the relationship between mother and child, humans interacting with dogs experience gaze-induced mutual oxytocin secretion and the longer the gaze, the higher the resulting oxytocin levels in both humans and dogs (and the better both feel). This hormonal interaction is called the oxytocin-gaze positive loop (we’ll refer to it as the OGPL for short). This diagram illustrates that steps that are involved in this positive feedback loop:
The Oxytocin-Gaze Positive Loop
Try a little experiment now. Sit down and gaze into your dog’s admiring eyes. Now think about how it makes you feel. It might seem silly, but just go ahead and do it. When you think about your feelings, do the words “calm,” “love,” “peaceful,” “happy,” and/or “content” come to mind? If they do, then you are experiencing the OGPL loop!
As a dog lover, I am sure that you can connect with the closing statement in the researchers’ publication: ”These results suggest that humans may feel affection for their companion dogs similar to that felt toward human family members…” You can’t help it – it’s a chemical attraction!
As a dog lover, I am sure that you can connect with the closing statement in the researchers’ publication: ”These results suggest that humans may feel affection for their companion dogs similar to that felt toward human family members…” You can’t help it – it’s a chemical attraction!
References
- Dölen G1, Darvishzadeh A, Huang KW, Malenka RC. Social reward requires coordinated activity of nucleus accumbens oxytocin and serotonin. Nature 2013;501(7466):179-84
- Neumann ID. Involvement of the brain oxytocin system in stress coping: interactions with the hypothalamo-pituitary-adrenal axis. Prog Brain Res 2002;139:147-62
- Odendaal JS, Meintjes RA. Neurophysiological correlates of affiliative behaviour between humans and dogs Vet J. 2003;165(3):296-301
- Nagasawa M, Mitsui S, En S, Ohtani N, Obta M, Sakuma Y, Onaka T, Mogi K, Kikusui T. Oxytocin-gaze positive loop and the coevolution of human-dog bonds. Science 2015;348(6232):333-336. Read PDF
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7-2-2019
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Is Your Dog a Social Butterfly?
What makes a dog a dog – that gregarious canine companion? People have been asking that for a very long time. Why is it that when you raise wolves with human care and companionship from the time they are born, while they are more comfortable around humans than wolves not raised with people, they never really become man’s/woman’s best friend?
This symbiotic relationship between dogs and humans began tens of thousands of years ago, with dogs getting room and board in exchange for light work such as vermin control. How did it morph into dogs becoming members of our extended families and part of our workforce? The answer to this question would help us better understand the nature of the human-canine bond and might hold the key to the process of domestication itself.
For decades, researchers believed that wolves with better social skills were gradually selected to live with humans and eventually became what we know as dogs. In that model, the difference between dogs and wolves is that dogs have greater behavioral plasticity (1). However, recent data suggests that wolves raised with and by humans can behave in a similar manner to dogs in social situations, meaning they may be more socially flexible than previously believed (2).
Recently, a group of scientists at Princeton and the National Institutes of Health decided to take a genetic approach to understanding the domestication of dogs. To do so, they compared the genomes of groups of animals with widely different characteristics – in this case, social behavior. They first surveyed the entire genomes of 701 dogs from 85 breeds and genomes of 92 grey wolves. This analysis revealed an area on chromosome 6 that was quite different between dogs and wolves (3). Interestingly, mutation of the genes in this region in humans is associated with a congenital disease called Williams-Beuren Syndrome (WBS) that is characterized by hypersociability. Affected people have an outgoing personality and interact readily with strangers without filter or restraint, like many dogs (think wet Golden Retrievers). The researchers recognized that a major difference between dogs and wolves is the exaggerated gregariousness of dogs and their increased propensity to initiate social contact, even with a different species. They began to think they were on to something!
Now the researchers needed to see whether those genetic differences between dogs and wolves corresponded with differences in social behavior. So they used a well-validated test of social behavior to compare domestic dogs (of several breeds) and captive, human-socialized wolves. The dogs or wolves were given 2 minutes to open a puzzle box containing summer sausage (yum!) in a room with a neutral stranger present. They recorded the percentage of time that was spent looking to the human for help solving the puzzle. Not surprisingly, dogs spent significantly more time than wolves looking to the human for assistance, a trait that they referred to as hypersociability.
Interestingly (but not surprisingly), the study also showed that dog breeds vary in the amount to which they look to humans. Some breeds were more likely to ask a human for help, while others worked more independently (see Table). Yes, there’s a dog for everyone!
This symbiotic relationship between dogs and humans began tens of thousands of years ago, with dogs getting room and board in exchange for light work such as vermin control. How did it morph into dogs becoming members of our extended families and part of our workforce? The answer to this question would help us better understand the nature of the human-canine bond and might hold the key to the process of domestication itself.
For decades, researchers believed that wolves with better social skills were gradually selected to live with humans and eventually became what we know as dogs. In that model, the difference between dogs and wolves is that dogs have greater behavioral plasticity (1). However, recent data suggests that wolves raised with and by humans can behave in a similar manner to dogs in social situations, meaning they may be more socially flexible than previously believed (2).
Recently, a group of scientists at Princeton and the National Institutes of Health decided to take a genetic approach to understanding the domestication of dogs. To do so, they compared the genomes of groups of animals with widely different characteristics – in this case, social behavior. They first surveyed the entire genomes of 701 dogs from 85 breeds and genomes of 92 grey wolves. This analysis revealed an area on chromosome 6 that was quite different between dogs and wolves (3). Interestingly, mutation of the genes in this region in humans is associated with a congenital disease called Williams-Beuren Syndrome (WBS) that is characterized by hypersociability. Affected people have an outgoing personality and interact readily with strangers without filter or restraint, like many dogs (think wet Golden Retrievers). The researchers recognized that a major difference between dogs and wolves is the exaggerated gregariousness of dogs and their increased propensity to initiate social contact, even with a different species. They began to think they were on to something!
Now the researchers needed to see whether those genetic differences between dogs and wolves corresponded with differences in social behavior. So they used a well-validated test of social behavior to compare domestic dogs (of several breeds) and captive, human-socialized wolves. The dogs or wolves were given 2 minutes to open a puzzle box containing summer sausage (yum!) in a room with a neutral stranger present. They recorded the percentage of time that was spent looking to the human for help solving the puzzle. Not surprisingly, dogs spent significantly more time than wolves looking to the human for assistance, a trait that they referred to as hypersociability.
Interestingly (but not surprisingly), the study also showed that dog breeds vary in the amount to which they look to humans. Some breeds were more likely to ask a human for help, while others worked more independently (see Table). Yes, there’s a dog for everyone!
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Breeds That Looked for Help
Bernese Mountain Dog
Border Collie
Boxer
Golden Retriever
Jack Russell Terrier
Miniature Poodle
Pug
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Breeds That Worked More Independently
Basenji
Cairn Terrier
Great Pyrenees
Malamute
Miniature Schnauzer
New Guinea Singing Dog
Pariah Dog
Saluki
Village Dogs from Puerto Rico
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Nonetheless, wolves (from North America, Europe, the Middle East, and China) were much less likely to look to the human for assistance that were the dogs, even wolves that were raised by people, thus taking the “nurture” component out of the equation.
Now that the researchers had their behavioral test, they examined whether this behavioral characteristic correlated with genetic changes in that area of the canine genome on chromosome 6 that correlated with hypersociability in humans. And the long and short of it is, they did correlate.
It turns out that the more hypersocial the dog was, the more their genes in that area of chromosome 6 were disrupted, or inactive. The disruptions appeared to be caused by jumping genes (aka transposable elements), sneaky little pieces of DNA that jump from one area of DNA to another. When that happens, the genes that are interrupted are unable to produce the protein they were designed to. The more of these jumping genes that were inserted in that area of chromosome 6, the greater percentage of time the dogs had looked to humans for help solving the puzzle.
We don’t yet know the exact functions of the genes in that area of the chromosome, and how they might relate to sociability in dogs. But there are hints. For example, one of the genes produces a protein that controls social context-related salivary oxytocin levels in humans. We know that oxytocin is released in both dogs and humans when they interact, so this might be one way in which the genes in this area modulate the human-animal bond.
As I was writing this article I was at a Nosework trial with my inexperienced Norwich Terrier, Helix. On the vehicle search, he ran up to the car and bounced his front feet up onto the running board, sniffed it and looked at me expectantly. I called it as an “alert,” – a signal from the dog to the handler that the hide was found – but guess what? He was just demonstrating hypersociability by looking to me for help. What a timely example! So I just made a mental note to study his body language better, felt the oxytocin flowing through my body and told him he was a good boy. After all, he can’t help it! It’s genetic!
Now that the researchers had their behavioral test, they examined whether this behavioral characteristic correlated with genetic changes in that area of the canine genome on chromosome 6 that correlated with hypersociability in humans. And the long and short of it is, they did correlate.
It turns out that the more hypersocial the dog was, the more their genes in that area of chromosome 6 were disrupted, or inactive. The disruptions appeared to be caused by jumping genes (aka transposable elements), sneaky little pieces of DNA that jump from one area of DNA to another. When that happens, the genes that are interrupted are unable to produce the protein they were designed to. The more of these jumping genes that were inserted in that area of chromosome 6, the greater percentage of time the dogs had looked to humans for help solving the puzzle.
We don’t yet know the exact functions of the genes in that area of the chromosome, and how they might relate to sociability in dogs. But there are hints. For example, one of the genes produces a protein that controls social context-related salivary oxytocin levels in humans. We know that oxytocin is released in both dogs and humans when they interact, so this might be one way in which the genes in this area modulate the human-animal bond.
As I was writing this article I was at a Nosework trial with my inexperienced Norwich Terrier, Helix. On the vehicle search, he ran up to the car and bounced his front feet up onto the running board, sniffed it and looked at me expectantly. I called it as an “alert,” – a signal from the dog to the handler that the hide was found – but guess what? He was just demonstrating hypersociability by looking to me for help. What a timely example! So I just made a mental note to study his body language better, felt the oxytocin flowing through my body and told him he was a good boy. After all, he can’t help it! It’s genetic!
References
- Frank H. Evolution of canine information processing under conditions of natural and artificial selection. Z Tierpsychol 1980;53:389-399.
- Udell MAR, Dorey NR, Wynne CDL. What did domestication do to dogs? A new account of dogs’ sensitivity to human actions. Biol Rev Camb Philos Soc 2010;85:327-345
- von Holdt BM, Shuldiner E, Koch IJ et al. Structural variants in genes associated with human Williams-Beuren syndrome underlie stereotypical huypersociability in domestic dogs. Sci Adv 2017;3:e1700398. Read PDF
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6-3-2019
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No Hot Dogs Please!
Not the kind you eat – you can make your own decisions about that! I’m talking literally: hot… dogs.
Maybe you are thinking, “Oh gosh, I already know everything about this topic: Don’t leave your dog in the car, dogs have less efficient cooling mechanisms than people, blah, blah, blah.” Well, bear with me, because there are a couple of new studies that just might surprise you. In fact, they might just save your dog’s life.
How Do Dogs Overheat?
There are just two basic ways your dog can become a hot dog – from external or internal factors.
External. This is the cause of overheating that we think of most often – dogs exposed to high temperatures and/or humidity, such as dogs left in cars or left out in a yard without shade.
Internal. Exercise generates heat. Muscle contraction and movement of the musculoskeletal system produce a tremendous amount of heat! In one study, activity was more important than temperature/humidity in contributing to heatstroke (1). Of course, if your dog is exercising in hot/humid temperatures, the risk of heat stroke is greatly amplified!
The Discomfort Index
There is a formula that takes temperature and humidity into account and produces a number called the Discomfort Index, or DI. At this link: https://keisan.casio.com/exec/system/1351058230, just plug in the current temperature and humidity and it will give you the corresponding DI – pretty cool (or maybe not)! One study showed that dogs are quite comfortable when the DI is less than 22, they are moderately uncomfortable when the DI is 22 to 28 and very uncomfortable when its above 28 (1).
How Do Dogs Cool?
We all know that the most important cooling system for dogs is evaporation of moisture from the upper respiratory tract – the mouth, nasal passages, pharynx, larynx, etc. (2). A second way that dogs cool is by dilating the blood vessels under the skin and expelling the heat from the vascular system through the skin.
Why Are Some Dogs More Susceptible to Heat?
1. Genetics. Susceptibility to overheating is partly genetic – a study of elite and poor-performing Alaskan Huskies identified a single region in the genome that was associated with heat tolerance (3).
2. Physical structure. Physical characteristics are also associated with the ability of dogs to cool. In one study, brachycephalic dogs (dogs with short faces, such as Pugs, Shih Tzu, etc.) were shown to have poorer cooling mechanisms (4). This is not surprising given that brachycephalic breeds have a shorter upper respiratory tract and often have folds of extra tissue in the oropharynx that can interfere with air flow.
3. Body Condition. The more surprising result of the above study was that poor body condition (using the Purina BCS measure) was more important than brachycephaly in a dog’s inability to cool. The higher the dog’s BCS, the warmer they got during exercise and the lower their tidal volume (air flow into the lungs) was. In addition, obese dogs are more likely to die if they do experience heatstroke (1). There’s yet another reason to keep your dog fit!
Track Your Dog’s Heat Susceptibility
I recommend keeping a record of your dog’s heat susceptibility. This is a simple matter of recording the following each time you take your dog outside:
What’s The Best Way to Cool a Dog?
A recent study compared three mechanisms for cooling dogs after 15 min treadmill exercise in a room at 30 degrees C (86 degrees F) (5). Dogs that were dipped in water for 5 minutes at ambient temperature had cooled in 16 minutes. Dogs that were placed in a kennel on a cooling mat at 4 degrees C (39 degrees F) with a fan took 36 minutes to cool. And dogs that were just in a kennel with a fan took 48 minutes to cool down. The authors suggested that water immersion is a method for not only treating but also for preventing overheating when dogs exercise.
Want to know more? We’ve prepared a 60-minute webinar that answers pretty well every hot (or cool) topic on the subject! Go to https://www.avidogzink.com/shop/webinars/keeping-your-dog-cool/. Of course, if you are a member of Fit For Life® or Fit To Be Tied ®, you get this and lots of other “cool” webinars free! Interested in learning more? Go to https://www.avidogzink.com/product-category/memberships/.
Maybe you are thinking, “Oh gosh, I already know everything about this topic: Don’t leave your dog in the car, dogs have less efficient cooling mechanisms than people, blah, blah, blah.” Well, bear with me, because there are a couple of new studies that just might surprise you. In fact, they might just save your dog’s life.
How Do Dogs Overheat?
There are just two basic ways your dog can become a hot dog – from external or internal factors.
External. This is the cause of overheating that we think of most often – dogs exposed to high temperatures and/or humidity, such as dogs left in cars or left out in a yard without shade.
Internal. Exercise generates heat. Muscle contraction and movement of the musculoskeletal system produce a tremendous amount of heat! In one study, activity was more important than temperature/humidity in contributing to heatstroke (1). Of course, if your dog is exercising in hot/humid temperatures, the risk of heat stroke is greatly amplified!
The Discomfort Index
There is a formula that takes temperature and humidity into account and produces a number called the Discomfort Index, or DI. At this link: https://keisan.casio.com/exec/system/1351058230, just plug in the current temperature and humidity and it will give you the corresponding DI – pretty cool (or maybe not)! One study showed that dogs are quite comfortable when the DI is less than 22, they are moderately uncomfortable when the DI is 22 to 28 and very uncomfortable when its above 28 (1).
How Do Dogs Cool?
We all know that the most important cooling system for dogs is evaporation of moisture from the upper respiratory tract – the mouth, nasal passages, pharynx, larynx, etc. (2). A second way that dogs cool is by dilating the blood vessels under the skin and expelling the heat from the vascular system through the skin.
Why Are Some Dogs More Susceptible to Heat?
1. Genetics. Susceptibility to overheating is partly genetic – a study of elite and poor-performing Alaskan Huskies identified a single region in the genome that was associated with heat tolerance (3).
2. Physical structure. Physical characteristics are also associated with the ability of dogs to cool. In one study, brachycephalic dogs (dogs with short faces, such as Pugs, Shih Tzu, etc.) were shown to have poorer cooling mechanisms (4). This is not surprising given that brachycephalic breeds have a shorter upper respiratory tract and often have folds of extra tissue in the oropharynx that can interfere with air flow.
3. Body Condition. The more surprising result of the above study was that poor body condition (using the Purina BCS measure) was more important than brachycephaly in a dog’s inability to cool. The higher the dog’s BCS, the warmer they got during exercise and the lower their tidal volume (air flow into the lungs) was. In addition, obese dogs are more likely to die if they do experience heatstroke (1). There’s yet another reason to keep your dog fit!
Track Your Dog’s Heat Susceptibility
I recommend keeping a record of your dog’s heat susceptibility. This is a simple matter of recording the following each time you take your dog outside:
- Dog’s Name
- Date and Time
- Temperature, Humidity and DI
- # Minutes of Exercise
- Strenuousness of Exercise (scale of 1 to 3)
- Dog’s Distress Level (on scale of 1 to 3, where 1 is slightly panting, 2 is moderate panting, and 3 is panting with the tongue curled).
What’s The Best Way to Cool a Dog?
A recent study compared three mechanisms for cooling dogs after 15 min treadmill exercise in a room at 30 degrees C (86 degrees F) (5). Dogs that were dipped in water for 5 minutes at ambient temperature had cooled in 16 minutes. Dogs that were placed in a kennel on a cooling mat at 4 degrees C (39 degrees F) with a fan took 36 minutes to cool. And dogs that were just in a kennel with a fan took 48 minutes to cool down. The authors suggested that water immersion is a method for not only treating but also for preventing overheating when dogs exercise.
Want to know more? We’ve prepared a 60-minute webinar that answers pretty well every hot (or cool) topic on the subject! Go to https://www.avidogzink.com/shop/webinars/keeping-your-dog-cool/. Of course, if you are a member of Fit For Life® or Fit To Be Tied ®, you get this and lots of other “cool” webinars free! Interested in learning more? Go to https://www.avidogzink.com/product-category/memberships/.
References
1. Bruchim et al. Heatstroke in dogs: A retrospective study of 54 cases (1999-2004) and analysis of risk factors for death. J Vet med 2006;20:38-46. Read the PDF
2. Dickerson et al. Wet mammals shake at tuned frequencies to dry. J R Soc Interface 2012;9:3208-3218 Read PDF
3. Huson et al. Breed-specific ancestry studies and genome-wide association analysis highlight an association between the MYH9 gene and heat tolerance in Alaskan sprint racing sled dogs. Mamm Genome 2012;23:178-194 Read PDF
4. Davis et al. Effect of brachycephaly and body condition score on respiratory thermoregulation of healthy dogs. J Am Vet Med Assoc 2017;251:1160-1165 Read PDF
5. Davis et al. Comparison of postexercise cooling methods in working dogs. J Spec Oper med 2019;19(1):56-60 Read PDF
2. Dickerson et al. Wet mammals shake at tuned frequencies to dry. J R Soc Interface 2012;9:3208-3218 Read PDF
3. Huson et al. Breed-specific ancestry studies and genome-wide association analysis highlight an association between the MYH9 gene and heat tolerance in Alaskan sprint racing sled dogs. Mamm Genome 2012;23:178-194 Read PDF
4. Davis et al. Effect of brachycephaly and body condition score on respiratory thermoregulation of healthy dogs. J Am Vet Med Assoc 2017;251:1160-1165 Read PDF
5. Davis et al. Comparison of postexercise cooling methods in working dogs. J Spec Oper med 2019;19(1):56-60 Read PDF
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5/7/2019
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Star Light, Star Bright…. Emerging Evidence that Light Therapy Can Improve Sports Performance
You’ve heard of the healing effects of laser therapy. There is strong scientific evidence that light can penetrate the skin and cell membranes and enter mitochondria (the energy producing factories of the cell). There, the light energy is converted into adenosine tri-phosphate (ATP), the form of energy that the cell uses for healing (1). This is a photochemical effect comparable to photosynthesis in plants whereby light is absorbed by a leaf and undergoes a chemical change to provide energy for the plant.
In a way, we shouldn’t really be surprised that light has power. We all know that sunlight can kill bacteria – Niels Ryberg Finsen won the Nobel Prize in medicine and physiology in 1903 for that discovery. Although laser technology was invented in the early 1960s, recently the field has exploded with studies demonstrating the healing effects of light therapy, more accurately called photobiomodulation therapy (PBMT). Hundreds of peer-reviewed studies show that PBMT can promote tissue regeneration, reduce inflammation and relieve pain in soft tissues such as muscles, tendons, and ligaments (2). In the last few years numerous studies have revealed that PBMT can improve hard-to-treat neurological and psychological conditions such as stroke, traumatic brain injury, Parkinson’s disease, and depression (3).
Now there is growing evidence that PBMT can actually improve muscle strength and enhance sports-related performance. That’s crazy you say? Let’s take a closer look at those studies.
A Bit of Background
No one hates physics more than I do, but actually it is pretty interesting (and simple) when we are talking about PBMT. So here are a few FAQs:
1. What forms of light can be used for PBMT?
Only light in the infrared or near infrared wavelengths (600 to 1064 nm) can be converted by the cell into energy. These wavelengths of light can be produced by lasers or LEDs. The main difference between the two is that lasers produce more photons and they are all aimed in one direction, whereas LEDs produce fewer photons that are emitted multidirectionally.
2. That’s a wide range of wavelengths. Does it make a difference what wavelength I choose?
In general, the longer the wavelength, the deeper into the tissue the light penetrates.
3. Since PBMT is a type of therapy, how do we measure doses?
When dosing with light, we use a unit of energy called the joule (J). One watt (W), or 1000 milliwatts (mW) of power, produces one joule per second. So, a typical laser with a power of 500 mW will produce one joule every 2 seconds. On the other hand, one LED light in a string of holiday lights has a power of approximately 70 mW, so it will take about 14 seconds for one of those lights to produce one joule of energy. When applying light therapy to a tissue, we describe dose exposure in J/cm2.
Studies of the Effects of PBMT on Performance
Remember that Hierarchy of Evidence, in which the best evidence consists of systematic reviews of randomized clinical trials? Well it just so happens that there is one such study examining the effects of PBMT on sports performance (4). How great is that? That study reviewed 46 randomized, placebo-controlled clinical trials that included 1045 participants. It concluded that PBMT can increase muscle mass gained after training and decrease inflammation and oxidative stress in muscles. They postulate that these effects are related to the fact that PBMT is known to increase ATP, the biological source of energy needed for muscle work. The review quotes many different studies that show improved performance of various muscle groups in humans, but let’s focus on one of the most practical, real-world studies – one that examined the effects of PBMT on the performance of high-level rugby players (5).
In that study, 12 male, world-class rugby players were treated with PBMT (using both lasers and LEDs) or placebo then run 7 times through a timed sprint test that included turns, much like an agility course. PBMT significantly improved the average time for all sprints as well as measured and perceived fatigue, and blood lactate levels (a by-product of muscle energy metabolism). Pretty cool!
When Can I Start Using Light Therapy?
Even though there is growing evidence of the benefits of PBMT on sports performance, there are many questions to be answered before you purchase a laser or LED therapy unit to turn your favorite furry athlete into a super-canine star. They are:
In a way, we shouldn’t really be surprised that light has power. We all know that sunlight can kill bacteria – Niels Ryberg Finsen won the Nobel Prize in medicine and physiology in 1903 for that discovery. Although laser technology was invented in the early 1960s, recently the field has exploded with studies demonstrating the healing effects of light therapy, more accurately called photobiomodulation therapy (PBMT). Hundreds of peer-reviewed studies show that PBMT can promote tissue regeneration, reduce inflammation and relieve pain in soft tissues such as muscles, tendons, and ligaments (2). In the last few years numerous studies have revealed that PBMT can improve hard-to-treat neurological and psychological conditions such as stroke, traumatic brain injury, Parkinson’s disease, and depression (3).
Now there is growing evidence that PBMT can actually improve muscle strength and enhance sports-related performance. That’s crazy you say? Let’s take a closer look at those studies.
A Bit of Background
No one hates physics more than I do, but actually it is pretty interesting (and simple) when we are talking about PBMT. So here are a few FAQs:
1. What forms of light can be used for PBMT?
Only light in the infrared or near infrared wavelengths (600 to 1064 nm) can be converted by the cell into energy. These wavelengths of light can be produced by lasers or LEDs. The main difference between the two is that lasers produce more photons and they are all aimed in one direction, whereas LEDs produce fewer photons that are emitted multidirectionally.
2. That’s a wide range of wavelengths. Does it make a difference what wavelength I choose?
In general, the longer the wavelength, the deeper into the tissue the light penetrates.
3. Since PBMT is a type of therapy, how do we measure doses?
When dosing with light, we use a unit of energy called the joule (J). One watt (W), or 1000 milliwatts (mW) of power, produces one joule per second. So, a typical laser with a power of 500 mW will produce one joule every 2 seconds. On the other hand, one LED light in a string of holiday lights has a power of approximately 70 mW, so it will take about 14 seconds for one of those lights to produce one joule of energy. When applying light therapy to a tissue, we describe dose exposure in J/cm2.
Studies of the Effects of PBMT on Performance
Remember that Hierarchy of Evidence, in which the best evidence consists of systematic reviews of randomized clinical trials? Well it just so happens that there is one such study examining the effects of PBMT on sports performance (4). How great is that? That study reviewed 46 randomized, placebo-controlled clinical trials that included 1045 participants. It concluded that PBMT can increase muscle mass gained after training and decrease inflammation and oxidative stress in muscles. They postulate that these effects are related to the fact that PBMT is known to increase ATP, the biological source of energy needed for muscle work. The review quotes many different studies that show improved performance of various muscle groups in humans, but let’s focus on one of the most practical, real-world studies – one that examined the effects of PBMT on the performance of high-level rugby players (5).
In that study, 12 male, world-class rugby players were treated with PBMT (using both lasers and LEDs) or placebo then run 7 times through a timed sprint test that included turns, much like an agility course. PBMT significantly improved the average time for all sprints as well as measured and perceived fatigue, and blood lactate levels (a by-product of muscle energy metabolism). Pretty cool!
When Can I Start Using Light Therapy?
Even though there is growing evidence of the benefits of PBMT on sports performance, there are many questions to be answered before you purchase a laser or LED therapy unit to turn your favorite furry athlete into a super-canine star. They are:
- What is the best wavelength to use?
- Is it better to apply PBMT to muscles before or after exercise?
- How long should the time interval between light therapy and exercise be?
- How many sites of irradiation should be used and on which muscle groups?
- What are the best power (mW) and dose (J/cm2) to use?
This last question is especially important because you might be thinking, “If low doses are beneficial, higher doses must be even more so!” Unfortunately, that is not the case. Numerous studies have shown that low doses of PBMT are beneficial, but higher doses can have no effect or might actually be harmful (3, 4). This biological process is called hormesis (see Figure below), just so you can impress your friends with your vocabulary. In any case, this little detail makes knowing the appropriate dose of PBMT really important!
This graph shows the hormesis effect, in which a low or moderate dose of a therapeutic (in this case photobiomodulation therapy) results in a positive effect, but as the dose becomes higher, the therapeutic has a negative effect.
Another important question to be answered is: how can we apply these bare-skinned human studies to our hairy dogs? How do we know how much of the light source will penetrate a dog’s coat to get to the skin? While a laser treatment can be applied by hand, parting the coat and ensuring that the skin is exposed to the light, this is not true for LED products, which usually consist of arrays of small LEDs in a stiff or flexible casement. The internet abounds with LED products that claim to treat a variety of problems in dogs (based loosely on the effects of PBMT in humans), but not one takes into account light penetration through the fur. With so many different densities of fur in different species, this is an important issue. Perhaps we should only use LED arrays on Chinese Crested Dogs or Xoloitzcuintlis!
An additional confounding factor is the fact that the darker the skin, the less the light penetrates to the tissues below (6). This factor also has only been studied in humans, not dogs. So if you have a hairy, dark-skinned dog, how much of the light is going to penetrate to the muscles where you want it to have its effect? We don’t know, but some have suggested less than 5%. So at this point, at least for dogs, PBMT to improve performance is not quite ready for primetime.
Despite all of these cautions, however, the evidence is quite convincing that, if you can get light of the right wavelength and power to penetrate to the muscle, it has the potential to significantly improve your dog’s athletic performance. The data in humans are so convincing that some studies suggest that PBMT be placed on the World Anti-Doping Agency’s list of prohibited substances (4), though how they will know whether a person has been treated has yet to come to light!
An additional confounding factor is the fact that the darker the skin, the less the light penetrates to the tissues below (6). This factor also has only been studied in humans, not dogs. So if you have a hairy, dark-skinned dog, how much of the light is going to penetrate to the muscles where you want it to have its effect? We don’t know, but some have suggested less than 5%. So at this point, at least for dogs, PBMT to improve performance is not quite ready for primetime.
Despite all of these cautions, however, the evidence is quite convincing that, if you can get light of the right wavelength and power to penetrate to the muscle, it has the potential to significantly improve your dog’s athletic performance. The data in humans are so convincing that some studies suggest that PBMT be placed on the World Anti-Doping Agency’s list of prohibited substances (4), though how they will know whether a person has been treated has yet to come to light!
References
1. Passarella S, Casamassima E, Molinari S, Pastore D, Quagliariello E, Catalano IM, Cingolani A. Increase of proton electrochemical potential and ATP synthesis in rat liver mitochondria irradiated in vitro by helium‐neon laser. FEBS Let 1984;175:95-99.
2. Alves AN, Fernandes KP, Deana AM, Bussadori SK, Mesquita-Ferrari RA Effects of low-level laser therapy on skeletal muscle repair: a systematic review. Am J Phys Med Rehabil. 2014;93(12):1073-85. Read PDF
3. Rojas JC, Gonzalez-Lima F. Neurological and psychological applications of transcranial lasers and LEDs. Biochemical Pharmacology 2013; 86:447–457. Read PDF
4. Ferraresi C, Huang Y-Y, Hamblin MR. Photobiomodulation in human muscle tissue: an advantage in sports performance? J Biophotonics 2016;9(11-12):1273-1299. Read PDF
5. Pinto HD, Vanin AA, Miranda EF, Tomazoni SS, Johnson DS, Albuquerque-Pontes GM, Alexio Junior I de O, Grandinetti V dos S, Casalechi HL, de Carvalho P de T C, Leal Junior ECP. Photobiomodulation therapy improves performance and accelerates recovery of high-level rugby players in field test: A randomized, crossover, double-blind, placebo-controlled clinical study. J Strength Cond Res 2016;30(12):3329-3338. Read PDF
6. Souza-Barros L, Dhaidan G, Maunula M, Solomon V, Gabison D, Lilge L, Nussbaum EL. Skin color and tissue thickness effects on transmittance, reflectance, and skin temperature when using 635 and 808nm lasers in low intensity therapeutics. Lasers Surg Med 2018;50:291-301.
2. Alves AN, Fernandes KP, Deana AM, Bussadori SK, Mesquita-Ferrari RA Effects of low-level laser therapy on skeletal muscle repair: a systematic review. Am J Phys Med Rehabil. 2014;93(12):1073-85. Read PDF
3. Rojas JC, Gonzalez-Lima F. Neurological and psychological applications of transcranial lasers and LEDs. Biochemical Pharmacology 2013; 86:447–457. Read PDF
4. Ferraresi C, Huang Y-Y, Hamblin MR. Photobiomodulation in human muscle tissue: an advantage in sports performance? J Biophotonics 2016;9(11-12):1273-1299. Read PDF
5. Pinto HD, Vanin AA, Miranda EF, Tomazoni SS, Johnson DS, Albuquerque-Pontes GM, Alexio Junior I de O, Grandinetti V dos S, Casalechi HL, de Carvalho P de T C, Leal Junior ECP. Photobiomodulation therapy improves performance and accelerates recovery of high-level rugby players in field test: A randomized, crossover, double-blind, placebo-controlled clinical study. J Strength Cond Res 2016;30(12):3329-3338. Read PDF
6. Souza-Barros L, Dhaidan G, Maunula M, Solomon V, Gabison D, Lilge L, Nussbaum EL. Skin color and tissue thickness effects on transmittance, reflectance, and skin temperature when using 635 and 808nm lasers in low intensity therapeutics. Lasers Surg Med 2018;50:291-301.
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4-2-2019
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The ‘Cure’ in Curcumin:
This Spice May Be The Solution to Your Dog's Lameness
Soft tissue (muscle, tendon, ligament) injuries are common in active dogs. In one study of agility dogs, 87% of all injuries involved soft tissues (1). Muscles heal quickly and generally return to full function, but tendons and ligaments are notoriously difficult to heal and frequently resolve by deposition of scar tissue, which impairs function.
Another common painful condition in active dogs is osteoarthritis, which is thought to affect 1 in 5 adult dogs in North America, and almost certainly affects an even higher proportion of active dogs (2).
Anything that claims to improve the lives of dogs with tendinopathy or arthritis is definitely worth checking out, so two studies of the effects of the spice curcumin on tendon healing and arthritis caught my attention. Earlier studies had suggested that curcumin might be used to treat chronic inflammatory illnesses such as neurodegenerative, cardiovascular, neoplastic, pulmonary, metabolic and autoimmune diseases (3). So let’s check out the results of those two studies.
1. Effects of Curcumin on Tendon Healing
In this study, investigators compared effects of curcumin on the healing of tendons in rats (4). They found that, in comparison to placebo-treated rat tendons, curcumin-treated rat tendons had:
1. More organized, parallel tendon collagen fibers. The placebo-treated rat tendons randomly oriented fibers, which resembled scar tissue (Fig 1).
2. More type I collagen, the main protein that gives tendons their strength.
3. Lower levels of MDA, a marker of tissue damage, and higher levels of MnSOD, a key anti-oxidant that prevents tissue damage.
4. Higher tensile strength.
Ok, so it looks like curcumin can improve the speed and quality of tendon healing in rats. But what about dogs?
Another common painful condition in active dogs is osteoarthritis, which is thought to affect 1 in 5 adult dogs in North America, and almost certainly affects an even higher proportion of active dogs (2).
Anything that claims to improve the lives of dogs with tendinopathy or arthritis is definitely worth checking out, so two studies of the effects of the spice curcumin on tendon healing and arthritis caught my attention. Earlier studies had suggested that curcumin might be used to treat chronic inflammatory illnesses such as neurodegenerative, cardiovascular, neoplastic, pulmonary, metabolic and autoimmune diseases (3). So let’s check out the results of those two studies.
1. Effects of Curcumin on Tendon Healing
In this study, investigators compared effects of curcumin on the healing of tendons in rats (4). They found that, in comparison to placebo-treated rat tendons, curcumin-treated rat tendons had:
1. More organized, parallel tendon collagen fibers. The placebo-treated rat tendons randomly oriented fibers, which resembled scar tissue (Fig 1).
2. More type I collagen, the main protein that gives tendons their strength.
3. Lower levels of MDA, a marker of tissue damage, and higher levels of MnSOD, a key anti-oxidant that prevents tissue damage.
4. Higher tensile strength.
Ok, so it looks like curcumin can improve the speed and quality of tendon healing in rats. But what about dogs?
Figure 1. Curcumin-treated rat tendons (right) had more organized fibers and more protein content (indicated by the deeper pink color) than the tendons of placebo-treated rats (left).
2. Effects of Curcumin on Osteoarthritis in Dogs
Before we look at this paper, we need to take a brief fantasy trip back to basic high school biology. Remember how you learned that genes are responsible for manufacturing all of the molecules in the body? Well, for these molecules to be made, genes have to be first activated or “expressed.” So one way to study the body’s reaction to a therapeutic is to measure the expression of various genes.
OK, back to curcumin. The second study compared genes that were up- or down-regulated in the white blood cells (WBC) of dogs with osteoarthritis treated either with curcumin or a nonsteroidal anti-inflammatory drug (5). WBCs are important because they play an active role in inflammation and healing throughout the body.
Twelve arthritic dogs were randomly assigned to two groups. Six dogs were treated with Previcox®, a nonsteroidal anti-inflammatory drug (NSAID) commonly used to reduce the pain and inflammation of arthritis. The other six were treated with curcumin at a dose of 4 mg per kilogram twice a day. WBCs from dogs before and 20 days after treatment were examined for the level of expression of genes that are associated with inflammation.
The results showed that curcumin essentially mimicked the anti-inflammatory and immune response activity of Previcox®. Remarkably, almost every gene that was up or down regulated by Previcox® was similarly up or down regulated by curcumin.
These two studies suggest that any time one of our dogs is diagnosed with a soft tissue injury such as a sprain or strain, or with arthritis, we should consider curcumin as an adjunctive therapy One way to administer curcumin to a dog is by making Golden Paste.
And finally, I don’t know about you, but with the arthritis that’s developing in my knees, I’m off to the grocery store!
Before we look at this paper, we need to take a brief fantasy trip back to basic high school biology. Remember how you learned that genes are responsible for manufacturing all of the molecules in the body? Well, for these molecules to be made, genes have to be first activated or “expressed.” So one way to study the body’s reaction to a therapeutic is to measure the expression of various genes.
OK, back to curcumin. The second study compared genes that were up- or down-regulated in the white blood cells (WBC) of dogs with osteoarthritis treated either with curcumin or a nonsteroidal anti-inflammatory drug (5). WBCs are important because they play an active role in inflammation and healing throughout the body.
Twelve arthritic dogs were randomly assigned to two groups. Six dogs were treated with Previcox®, a nonsteroidal anti-inflammatory drug (NSAID) commonly used to reduce the pain and inflammation of arthritis. The other six were treated with curcumin at a dose of 4 mg per kilogram twice a day. WBCs from dogs before and 20 days after treatment were examined for the level of expression of genes that are associated with inflammation.
The results showed that curcumin essentially mimicked the anti-inflammatory and immune response activity of Previcox®. Remarkably, almost every gene that was up or down regulated by Previcox® was similarly up or down regulated by curcumin.
These two studies suggest that any time one of our dogs is diagnosed with a soft tissue injury such as a sprain or strain, or with arthritis, we should consider curcumin as an adjunctive therapy One way to administer curcumin to a dog is by making Golden Paste.
And finally, I don’t know about you, but with the arthritis that’s developing in my knees, I’m off to the grocery store!
References
1. Cullen KL, Dickey JP, Bent LR, Thomason JJ, Moens NMM. Internet-based survey of the nature and perceived causes of injury to dogs participating in agility training and competition events. J Am Vet Med Assoc 2013;243:1010-1018. Read the PDF
2. Fleming JM, Creevy KE, Promislow DEL. Mortality in North American dogs from 1984 to 2004: An investigation into age-, size- and breed-related causes of death. J Vet Intern Med 2011:25:187-198. Read the PDF
3. Aggarwal BB. Harikumar K. Potential therapeutic effects of curcumin, the anti-inflammatory agent, against neurodegenerative, cardiovascular, pulmonary, metabolic, autoimmune and neoplastic diseases. Int J Biochem Cell Biol 2009;41:40–59. Read the PDF
4. Jiang D, Gao P, Lin H, Geng H. Curcumin improves tendon healing in rats: a histological, biochemical, and functional evaluation. Connect Tissue Res. 2016;57(1):20-7. Read the PDF
5. Colitti M, Gaspardo B, Della Pria A, Scaini C, Stefanon B. Transcriptome modification of white blood cells after dietary administration of curcumin and non-steroidal anti-inflammatory drug in osteoarthritic affected dogs. Veterinary Immunology and Immunopathology 2012;147:136-146. Read the PDF
2. Fleming JM, Creevy KE, Promislow DEL. Mortality in North American dogs from 1984 to 2004: An investigation into age-, size- and breed-related causes of death. J Vet Intern Med 2011:25:187-198. Read the PDF
3. Aggarwal BB. Harikumar K. Potential therapeutic effects of curcumin, the anti-inflammatory agent, against neurodegenerative, cardiovascular, pulmonary, metabolic, autoimmune and neoplastic diseases. Int J Biochem Cell Biol 2009;41:40–59. Read the PDF
4. Jiang D, Gao P, Lin H, Geng H. Curcumin improves tendon healing in rats: a histological, biochemical, and functional evaluation. Connect Tissue Res. 2016;57(1):20-7. Read the PDF
5. Colitti M, Gaspardo B, Della Pria A, Scaini C, Stefanon B. Transcriptome modification of white blood cells after dietary administration of curcumin and non-steroidal anti-inflammatory drug in osteoarthritic affected dogs. Veterinary Immunology and Immunopathology 2012;147:136-146. Read the PDF
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3-5-2019
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Scents of Success
The extraordinary olfactory abilities of dogs have long been used by humans for odor identification and discrimination. Our use of this incredible canine tool, which we are completely unable to imitate or engineer, is continuously expanding. We deploy the canine nose for life-and-death activities such as improving our safety (e.g., bomb and drug detection, tracking lost individuals, avalanche work) and our health (e.g., cancer detection, diabetes/seizure alert). We also use the dog’s exceptional scenting ability for recreation as we hunt game and play novel games involving scent detection (e.g., nose/scent work, utility obedience, tracking, hunt tests/field trials).
Given the importance of the dog’s superlative schnoz, it’s important to understand what factors might alter its function. What about physical stressors such as exercise, conditioning, diet and environment?
Several studies provide important information about what dogs need to be at their scenting best and reveal clues about how we can optimize olfaction!
Factors That Can Affect Scents-Ability in Dogs
1. Conditioning
Some people are surprised that conditioning can affect a dog’s scenting ability. I mean, what does the strength of a dog’s muscles have to do with the ability of odor molecules to land on the receptors in the nose and transmit a neurological signal to the brain? However, fitness is one of the most important factors in your dog’s odor detection ability. In one study, dogs that were less fit had an astounding 64% reduction in their scent sensitivity compared to physically conditioned dogs (1)! Another showed a higher frequency of correct target alerts in physically fit dogs (2). This might be related to the lower heart rate in conditioned dogs and therefore a reduction in the need for panting (which reduces olfaction because of reduced airflow through the nose).
2. Diet
There are just a few studies of the effects of diet on scenting ability in dogs, but they offer some fascinating insights into the potential for improving scenting ability through appropriate nutrition. English Pointers withheld from exercise and fed a diet supplemented with coconut oil appeared to experience compromised olfaction, but exercised dogs maintained their olfactory acuity (3) – another reason to keep your dog fit!
Another study showed benefits to olfaction when using a corn oil-supplemented diet and exercise – there’s that fitness component again (1)! A third study looked at “the breakfast effect” in which dogs searched more accurately 30 min following the consumption of breakfast than when fasted. They concluded that food might provide energy for cognitive processes, and that search accuracy in fasted dogs decreased as a function of energy depletion (4).
3. Environment
Factors that lead to heat stress including lack of acclimatization to a novel environment, increased environmental temperature, increased humidity, lack of access to water, and/or poor ventilation, all contribute to reduced odor detection ability (5). A dog that is heat stressed will pant, which itself reduces olfaction due to reduced airflow through the nose. In addition, dehydration can significantly decrease odor detection capabilities in dogs (3).
4. Age
Older dogs can have age-related changes in their scenting system, similar to that experienced by aged people (6). Older dogs had a reduced number of odor-detecting cells in their noses and the cells that remained had a reduced number of cilia (the tiny hairs that contain odor receptors, which grab odor molecules out of the air). Scent detection games can provide excellent environmental stimulation for old dogs, though, so don’t let this possible deficiency stop you from providing your oldster with odoriferous experiences. Just make sure the odors are strong!
5. Drugs
There is a long list of pharmaceuticals that can cause reduced olfaction in humans including anesthetics, antiarrhythmics, antihistamines, antimicrobials, antiproliferative and immuno-suppressive drugs, endocrine drugs, gastrointestinal (GI) drugs, neurologic drugs, and NSAIDs (7, 8, 9). The list of drugs that have been proven to affect scenting ability in dogs is shorter because of a lack of research. Those include some cardiac drugs, high doses of metronidazole, steroids, and chemotherapeutics (10). Regardless, it is important to consider that any dog being treated with a pharmaceutical might have diminished scenting ability.
6. Subclinical or Chronic Diseases
Interestingly, endocrine conditions such as hypothyroidism, diabetes and Cushing’s disease can cause a lack of scenting ability in dogs (11). The mechanism for this is unknown, but given that many dogs live with these chronic conditions, it is important to ensure that the dog is getting the best current therapy for the condition, which should minimize the risk of effects on olfaction. If your dog is living with one of these conditions, consider that they might be less efficient at scenting.
It might seem worrisome that there are so many factors that can affect your dog’s scents-ability, but the good news is that, with a little knowledge and forethought, you can substantially reduce the risk of odor detection deficiencies and even help your dog establish and maintain superlative scenting skills!
Given the importance of the dog’s superlative schnoz, it’s important to understand what factors might alter its function. What about physical stressors such as exercise, conditioning, diet and environment?
Several studies provide important information about what dogs need to be at their scenting best and reveal clues about how we can optimize olfaction!
Factors That Can Affect Scents-Ability in Dogs
1. Conditioning
Some people are surprised that conditioning can affect a dog’s scenting ability. I mean, what does the strength of a dog’s muscles have to do with the ability of odor molecules to land on the receptors in the nose and transmit a neurological signal to the brain? However, fitness is one of the most important factors in your dog’s odor detection ability. In one study, dogs that were less fit had an astounding 64% reduction in their scent sensitivity compared to physically conditioned dogs (1)! Another showed a higher frequency of correct target alerts in physically fit dogs (2). This might be related to the lower heart rate in conditioned dogs and therefore a reduction in the need for panting (which reduces olfaction because of reduced airflow through the nose).
2. Diet
There are just a few studies of the effects of diet on scenting ability in dogs, but they offer some fascinating insights into the potential for improving scenting ability through appropriate nutrition. English Pointers withheld from exercise and fed a diet supplemented with coconut oil appeared to experience compromised olfaction, but exercised dogs maintained their olfactory acuity (3) – another reason to keep your dog fit!
Another study showed benefits to olfaction when using a corn oil-supplemented diet and exercise – there’s that fitness component again (1)! A third study looked at “the breakfast effect” in which dogs searched more accurately 30 min following the consumption of breakfast than when fasted. They concluded that food might provide energy for cognitive processes, and that search accuracy in fasted dogs decreased as a function of energy depletion (4).
3. Environment
Factors that lead to heat stress including lack of acclimatization to a novel environment, increased environmental temperature, increased humidity, lack of access to water, and/or poor ventilation, all contribute to reduced odor detection ability (5). A dog that is heat stressed will pant, which itself reduces olfaction due to reduced airflow through the nose. In addition, dehydration can significantly decrease odor detection capabilities in dogs (3).
4. Age
Older dogs can have age-related changes in their scenting system, similar to that experienced by aged people (6). Older dogs had a reduced number of odor-detecting cells in their noses and the cells that remained had a reduced number of cilia (the tiny hairs that contain odor receptors, which grab odor molecules out of the air). Scent detection games can provide excellent environmental stimulation for old dogs, though, so don’t let this possible deficiency stop you from providing your oldster with odoriferous experiences. Just make sure the odors are strong!
5. Drugs
There is a long list of pharmaceuticals that can cause reduced olfaction in humans including anesthetics, antiarrhythmics, antihistamines, antimicrobials, antiproliferative and immuno-suppressive drugs, endocrine drugs, gastrointestinal (GI) drugs, neurologic drugs, and NSAIDs (7, 8, 9). The list of drugs that have been proven to affect scenting ability in dogs is shorter because of a lack of research. Those include some cardiac drugs, high doses of metronidazole, steroids, and chemotherapeutics (10). Regardless, it is important to consider that any dog being treated with a pharmaceutical might have diminished scenting ability.
6. Subclinical or Chronic Diseases
Interestingly, endocrine conditions such as hypothyroidism, diabetes and Cushing’s disease can cause a lack of scenting ability in dogs (11). The mechanism for this is unknown, but given that many dogs live with these chronic conditions, it is important to ensure that the dog is getting the best current therapy for the condition, which should minimize the risk of effects on olfaction. If your dog is living with one of these conditions, consider that they might be less efficient at scenting.
It might seem worrisome that there are so many factors that can affect your dog’s scents-ability, but the good news is that, with a little knowledge and forethought, you can substantially reduce the risk of odor detection deficiencies and even help your dog establish and maintain superlative scenting skills!
References
1. Angle CT, Wakshlag JJ, Gillette RL, Steury T, Haney P, Barrett J, Fischer T. The effects of exercise and diet on olfactory capability in detection dogs. J Nutr Sci 2014;3:e44 Read the PDF
2. Gazit I, Terkel J. Explosives detection by sniffer dogs following strenuous physical activity. Appl Anim Behav Sci 2003;81:149-61 Read the PDF
3. Altom EK, Davenport GM, Myers LJ, Cummins KA. Effect of dietary fat source and exercise on odorant-detecting ability of canine athletes. Research in Veterinary Science 2003;75:149–155 Read the PDF
4. Miller HC, Bender C. The breakfast effect: Dogs (Canis familiaris) search more accurately when they are less hungry. Behav Proc 2012;91:313-317 Read the PDF
5. Andress M, Goodnight ME. Heatstroke in a military working dog. US Army Med Dep J 2013;1:34-7
6. Hirai T, Kojima S, Shimada A. Age-related changes in the olfactory system of dogs. Neuropathol Appl Neurobiol 1996;22(6):532-9
7. Bromley SM. Smell and taste disorders: a primary care approach. Am Fam Physician 2000;61:427-36
8. McNeill EJM, Carrie S. Olfactory dysfunction – assessment and management J ENT Masterclass 2009;2:68-73
9. Scott AE. Clinical characteristics of taste and smell disorders. Ear Nose Throat J 1989;68:297-298,301,304-21
10. Jenkins EK, Lee-Fowler TM, Angle TC, Behrend EN, Moore GE. Effects of oral administration of metronidazole and doxycycline on olfactory capabilities of explosives detection dogs. Am J Vet Res 2016;77:906-12.
11. Myers LJ. Dysosmia of the dog in clinical veterinary medicine. Prog Vet Neurol 1990;1:171-9
2. Gazit I, Terkel J. Explosives detection by sniffer dogs following strenuous physical activity. Appl Anim Behav Sci 2003;81:149-61 Read the PDF
3. Altom EK, Davenport GM, Myers LJ, Cummins KA. Effect of dietary fat source and exercise on odorant-detecting ability of canine athletes. Research in Veterinary Science 2003;75:149–155 Read the PDF
4. Miller HC, Bender C. The breakfast effect: Dogs (Canis familiaris) search more accurately when they are less hungry. Behav Proc 2012;91:313-317 Read the PDF
5. Andress M, Goodnight ME. Heatstroke in a military working dog. US Army Med Dep J 2013;1:34-7
6. Hirai T, Kojima S, Shimada A. Age-related changes in the olfactory system of dogs. Neuropathol Appl Neurobiol 1996;22(6):532-9
7. Bromley SM. Smell and taste disorders: a primary care approach. Am Fam Physician 2000;61:427-36
8. McNeill EJM, Carrie S. Olfactory dysfunction – assessment and management J ENT Masterclass 2009;2:68-73
9. Scott AE. Clinical characteristics of taste and smell disorders. Ear Nose Throat J 1989;68:297-298,301,304-21
10. Jenkins EK, Lee-Fowler TM, Angle TC, Behrend EN, Moore GE. Effects of oral administration of metronidazole and doxycycline on olfactory capabilities of explosives detection dogs. Am J Vet Res 2016;77:906-12.
11. Myers LJ. Dysosmia of the dog in clinical veterinary medicine. Prog Vet Neurol 1990;1:171-9
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2-5-2019
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To Harness or Not To Harness? That is the Question
… that was addressed by a recent study that is the topic of this month’s newsletter. You’ve probably noticed an upsurge during the last several years in the use of harnesses as an alternative to collars. At the same time, there has been a concern that harnesses might affect dogs’ gait. Researchers in the UK investigated exactly that question by comparing the effect of restrictive and non-restrictive harnesses on shoulder extension in dogs when walking and trotting (1).
There are two main categories of harnesses: those that are considered non-restrictive to front limb movement, which have a Y-shaped chest strap (Fig. 1), and those considered restrictive, which have a strap that lies across the chest horizontally (Fig. 2).
There are two main categories of harnesses: those that are considered non-restrictive to front limb movement, which have a Y-shaped chest strap (Fig. 1), and those considered restrictive, which have a strap that lies across the chest horizontally (Fig. 2).
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Figure 1. Example of a non-restrictive harness. These have a Y-shaped component that should lie over the manubrium (front of the sternum).
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Figure 2. Example of a restrictive harness. These generally have a horizontal strap that runs over the shoulder joint or the scapula (shoulder blade) and across the chest/neck of the dog.
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In this study, 9 dogs were moved at a walk and a trot on a treadmill wearing either no harness, a non-restrictive harness (an X-back mushing harness; Trixie Fusion harness), or a restrictive harness (Easy Walk harness). The researchers placed markers on the sides of the dogs’ legs and used video cameras to measure the angle of the shoulder when the front limb was in maximal extension (when the leg was placed furthest forward).
Some of their results were unexpected!
Results of the Study: No harness vs. non-restrictive harness vs. restrictive harness
The researchers also examined the effect of weights added to the harness to try to simulate the dog pulling against the harness. The weights were used in a way that caused the harness to be pulled up and away from the dog’s back at an approximately 45o angle, similar to how the harness would be pulled on if a person were walking behind the dog.
Results of the Study: Weights vs. No Weights
The authors are to be commended for performing this important study and for their excellent discussion of the results.
One limitation of the study mentioned by the authors was that their system was not designed to measure step or stride length or stance time, which can affect shoulder extension. However, a previous harness study did look at those parameters (2). That study showed that both non-restrictive and restrictive harnesses alter step and stride length as compared to the same dogs wearing just a collar.
Questions, Questions…
Some of their results were unexpected!
Results of the Study: No harness vs. non-restrictive harness vs. restrictive harness
- Dogs wearing only a collar had significantly more shoulder extension, both while walking and trotting, than dogs wearing either type of harness.
- Dogs wearing non-restrictive harnesses had significantly less shoulder extension than dogs wearing restrictive harnesses when both walking and trotting. That was the unexpected finding, and we’ll look at those results more closely in a minute.
The researchers also examined the effect of weights added to the harness to try to simulate the dog pulling against the harness. The weights were used in a way that caused the harness to be pulled up and away from the dog’s back at an approximately 45o angle, similar to how the harness would be pulled on if a person were walking behind the dog.
Results of the Study: Weights vs. No Weights
- Dogs walking using non-restrictive harnesses with weights had significantly less shoulder extension than dogs wearing non-restrictive harnesses without weights or than those wearing restrictive harnesses with or without weights.
- Dogs trotting using non-restrictive harnesses with weights had significantly less shoulder extension than dogs wearing restrictive harnesses with or without weights.
The authors are to be commended for performing this important study and for their excellent discussion of the results.
One limitation of the study mentioned by the authors was that their system was not designed to measure step or stride length or stance time, which can affect shoulder extension. However, a previous harness study did look at those parameters (2). That study showed that both non-restrictive and restrictive harnesses alter step and stride length as compared to the same dogs wearing just a collar.
Questions, Questions…
1. Why would the so-called non-restrictive harness reduce shoulder extension more than the restrictive harness?
A: In my opinion, it might be a function of harness fit. As you can see in Figure 3 (taken from the publication but with arrows added), the non-restrictive harness is not ideally fitted to the dog. The straps that lie in front of the scapula (shoulder blade) are pressing into the dog’s body (arrows), almost certainly preventing the dog from moving its scapula forward. This, of course, would limit shoulder extension.
A non-restrictive harness needs to be fitted so that it is tight around the dog’s neck. That way, when the dog is pulling, the Y-shaped chest strap applies pressure to the manubrium (the front of the sternum), and the straps on the side of the neck should not slide back to lie against the shoulder blade. For most dogs, this means that the neck part of the harness needs to be adjustable and needs to have a clip, so that it doesn’t have to be large enough to slip over the dog’s head.
2. Why would the addition of weights to the non-restrictive harness further reduce the dog’s shoulder extension?
A: See answer to question 1. I think that when the weights pulled on the harness, those loose side straps pulled even harder against the dog’s shoulder blades, further restricting shoulder extension.
3. Why would the addition of weights to the restrictive harness allow the dog to have more shoulder extension?
A: It is likely that the weights pulling upwards and backwards on the restrictive harness allowed the horizontal band to rise up on the dog’s front, taking some of the pressure of that band off of the shoulder joint (Fig. 4). This would allow the dog to extend its shoulder further (although it might put more pressure on the dog’s neck).
A: In my opinion, it might be a function of harness fit. As you can see in Figure 3 (taken from the publication but with arrows added), the non-restrictive harness is not ideally fitted to the dog. The straps that lie in front of the scapula (shoulder blade) are pressing into the dog’s body (arrows), almost certainly preventing the dog from moving its scapula forward. This, of course, would limit shoulder extension.
A non-restrictive harness needs to be fitted so that it is tight around the dog’s neck. That way, when the dog is pulling, the Y-shaped chest strap applies pressure to the manubrium (the front of the sternum), and the straps on the side of the neck should not slide back to lie against the shoulder blade. For most dogs, this means that the neck part of the harness needs to be adjustable and needs to have a clip, so that it doesn’t have to be large enough to slip over the dog’s head.
2. Why would the addition of weights to the non-restrictive harness further reduce the dog’s shoulder extension?
A: See answer to question 1. I think that when the weights pulled on the harness, those loose side straps pulled even harder against the dog’s shoulder blades, further restricting shoulder extension.
3. Why would the addition of weights to the restrictive harness allow the dog to have more shoulder extension?
A: It is likely that the weights pulling upwards and backwards on the restrictive harness allowed the horizontal band to rise up on the dog’s front, taking some of the pressure of that band off of the shoulder joint (Fig. 4). This would allow the dog to extend its shoulder further (although it might put more pressure on the dog’s neck).
Figure 3. This shows the experimental set-up for dogs using non-restrictive harnesses in the Lafuente study. The white lines show how the angle of maximum shoulder extension was measured. The yellow arrows show the harness pressing into the dog’s body in front of the scapula, which likely would prevent the shoulder blade from freely sliding forward when the dog is wearing this harness, This would reduce the angle of shoulder extension.
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Figure 4. This shows the experimental set-up for dogs using restrictive harnesses in the Lafuente study. The yellow arrow indicates the direction in which the harness might move when a weight that pulls upward and backward at a 45o angle is attached to the harness. This would reduce pressure on the shoulder joint, but might put increased pressure on the dog’s neck.
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Bottom Line:
- Harnesses are still a safer option for dogs that have tracheal collapse, laryngeal paralysis, obstructive airway disease or neurological problems involving the neck, such as wobblers disease.
- Because two studies now provide good evidence that both restrictive and non-restrictive harnesses alter dogs’ gaits, a collar might be a better choice for many dogs. However, dogs wearing collars should be trained to walk politely, without pulling, on a leash. An excellent booklet that shows how to do this is My Dog Pulls. What Do I Do? By Turid Rugaas (3).
- If you choose to use a non-restrictive harness, make sure it is tightly fitted around the dog’s neck so that it doesn’t slide back and put pressure on the dog’s shoulders.
- If you choose to use a restrictive harness, make sure it is loosely fitted, so that it can slide away from the dog’s shoulder as needed.
References
1. Lafuente MP, Provis L, Schmalz EA. Effects of restrictive and non-restrictive harnesses on shoulder extension in dogs at walk and trot. Vet Record 2018;1-7. doi: 10.1136/vr.104946 Read the PDF
2. Carr BJ, Dresse K, Zink MC. The effects of five commercially available harnesses on
canine gait. Proceedings of ACVS Surgical Summit, 2016. Read the PDF
3. Rugaas T. My Dog Pulls. What Do I Do? 2005. Dogwise Publishing.
2. Carr BJ, Dresse K, Zink MC. The effects of five commercially available harnesses on
canine gait. Proceedings of ACVS Surgical Summit, 2016. Read the PDF
3. Rugaas T. My Dog Pulls. What Do I Do? 2005. Dogwise Publishing.
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1-1-2019
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How to Make Your Dog More Optimistic
Research across many species, from rats to dogs to zoo animals, show that their attitude towards life, positive or negative, affects their welfare, mental health, ability to learn and remember, and the quality of their decisions. Negative attitudes are often tied to separation anxiety or dog-directed fear and aggression. So, we want our dogs to have a positive attitude not only because it makes them happier but also because it increases mental stability, improves how easily their learn, remember, and make good decisions about situations they find themselves in. Read on to find out how one of the newest dog sports improves dogs’ optimism and with it, all of these benefits.
Cognitive Bias
We all know people who are ‘glass half-full’ types – they look at life from a positive viewpoint and generally are fun to be with. And of course, there are the ‘glass half-empty’ types, who always seem pessimistic and can be kind of a downer to spend time with.
This attitude toward life is referred to as cognitive bias (also called judgment bias), and it has huge implications for mental health, as well as learning and memory. Cognitive bias has a significant influence on behavior and decision-making. In fact, changing a person’s cognitive bias is a core feature of cognitive behavioral therapy, one of the most well-founded therapeutic interventions for improving mental health.
Cognitive bias is measured in humans using a language-based test. Cognitive bias testing in animals consists of training the animal to discriminate between two stimuli: one associated with a positive event (e.g. food reward), the other associated with a negative event, such as disgusting food, a fear-eliciting object, or the absence of a reward. The animal is then given an ambiguous stimulus and its behavior observed.
Cognitive bias testing has shown that rats living in unpredictable living conditions expect less positive outcomes than rats living in predictable conditions (1). Sheep that are released from restraint have a more positive cognitive bias (2). Pigs in an enriched environment are more optimistic than pigs in a less enriched environment (3). Even honeybees demonstrate cognitive bias – those from hives that were shaken were more likely to drink from flowers containing a liquid that contained less sugar than those from a stable hive (4).
Cognitive Bias Testing In Dogs
To test cognitive bias in dogs, a dog is seated about 10’ (3m) from a 6’ (2m) line placed perpendicular to the dog and owner (see figure). When a bowl is placed at one end of the line (the positive end), it contains great food. When placed at the other end of the 6’ line (the negative end), it is empty. Then an empty bowl is placed in the middle of the 6’ line and the dog is observed to see how many seconds it takes to approach the bowl (5).
Cognitive Bias
We all know people who are ‘glass half-full’ types – they look at life from a positive viewpoint and generally are fun to be with. And of course, there are the ‘glass half-empty’ types, who always seem pessimistic and can be kind of a downer to spend time with.
This attitude toward life is referred to as cognitive bias (also called judgment bias), and it has huge implications for mental health, as well as learning and memory. Cognitive bias has a significant influence on behavior and decision-making. In fact, changing a person’s cognitive bias is a core feature of cognitive behavioral therapy, one of the most well-founded therapeutic interventions for improving mental health.
Cognitive bias is measured in humans using a language-based test. Cognitive bias testing in animals consists of training the animal to discriminate between two stimuli: one associated with a positive event (e.g. food reward), the other associated with a negative event, such as disgusting food, a fear-eliciting object, or the absence of a reward. The animal is then given an ambiguous stimulus and its behavior observed.
Cognitive bias testing has shown that rats living in unpredictable living conditions expect less positive outcomes than rats living in predictable conditions (1). Sheep that are released from restraint have a more positive cognitive bias (2). Pigs in an enriched environment are more optimistic than pigs in a less enriched environment (3). Even honeybees demonstrate cognitive bias – those from hives that were shaken were more likely to drink from flowers containing a liquid that contained less sugar than those from a stable hive (4).
Cognitive Bias Testing In Dogs
To test cognitive bias in dogs, a dog is seated about 10’ (3m) from a 6’ (2m) line placed perpendicular to the dog and owner (see figure). When a bowl is placed at one end of the line (the positive end), it contains great food. When placed at the other end of the 6’ line (the negative end), it is empty. Then an empty bowl is placed in the middle of the 6’ line and the dog is observed to see how many seconds it takes to approach the bowl (5).
Now, you might be thinking, “Of course the dog will approach the bowl to see whether a great treat might be waiting there!” But a recent study showed that dogs that scored higher on traits such as sociability, excitability and lower in non-social fear ran more quickly towards the ambiguous bowl and thus were considered to have a more optimistic bias than dogs with separation anxiety or dog-directed fear and aggression, who were judged to be more pessimistic (6).
Cognitive Bias in Dogs Trained in Nosework vs. Heeling
A recently published study used cognitive bias testing to compare dogs that had been trained in nosework vs. heeling (7). Here is how they did the study. Twenty dogs were trained in the cognitive bias test, so they knew where to go to get the good treat, and they knew that the other bowl was empty. The dogs were then randomly assigned to groups of 10 dogs each and both groups of dogs were tested for their cognitive bias by placing the bowl in the ambiguous position and the amount of time it took them to get to the bowl was recorded. There were no differences between the groups in this initial test.
Then one group of dogs spent two weeks being trained in nosework, while the other group was trained in heeling. Both groups of dogs spent the same amount of time training with their owners, the same amount of time being active, and ingested the same quantity of food during training. The groups were then re-tested for cognitive bias. The outcome measure was how many seconds it took the dogs to go to the ambiguous bowl after training as compared to before training.
Results
Dogs that had been trained in nosework approached the ambiguous bowl significantly faster than they did before whereas there was no difference for the dogs trained in heeling. The authors concluded that the dogs that were trained in nosework had a more “optimistic” outlook. They postulate that pet dogs generally cannot engage in natural behaviors such as foraging, which free-range dogs spend 10 to 22% of their time doing. They quote a number of studies that demonstrate that foraging is a natural behavior of many species including dogs and is a form of environmental enrichment important for animal welfare.
Conclusion
So how cool is this? Playing scenting games with our dogs, such as nosework, makes
their cognitive bias more positive. Future research will have to confirm the final
outcomes but if dogs are like other species, that more positive attitude will make them
more optimistic about life, increase their mental stability, improve how easily they learn
and remember, and improve their decision making.
Comments
OK, I know what you’re thinking – the dogs that were trained in nosework were clearly trained to look into boxes for food, so of course they went more quickly towards the ambiguous bowl in hopes of finding food. Well, it should be noted that the dogs in both groups were just as effective in identifying, and approaching or not, the positive and negative bowls during the cognitive bias testing – only their behavior towards the ambiguous bowl differed. That suggests that there wasn’t an effect of being trained to go and investigate bowls.
This study suggests that foraging (looking for and consuming food) is stimulating and intrinsically rewarding to dogs. Thus, increasing your dog’s foraging time, whether that means teaching nosework or scent work formally or just as a game to play around the house and yard, or using food-distributing toys might actually increase your dog’s optimism and outlook toward life.
And just as an extra note: oxytocin has been found to improve cognitive bias in dogs too (8). So all that time you spend petting, making eye contact, and telling your dog you love him/her (which has been shown to induce secretion of oxytocin in both human and dog) – that’s improving both your AND your dog’s outlook on life! I’m all for that
Cognitive Bias in Dogs Trained in Nosework vs. Heeling
A recently published study used cognitive bias testing to compare dogs that had been trained in nosework vs. heeling (7). Here is how they did the study. Twenty dogs were trained in the cognitive bias test, so they knew where to go to get the good treat, and they knew that the other bowl was empty. The dogs were then randomly assigned to groups of 10 dogs each and both groups of dogs were tested for their cognitive bias by placing the bowl in the ambiguous position and the amount of time it took them to get to the bowl was recorded. There were no differences between the groups in this initial test.
Then one group of dogs spent two weeks being trained in nosework, while the other group was trained in heeling. Both groups of dogs spent the same amount of time training with their owners, the same amount of time being active, and ingested the same quantity of food during training. The groups were then re-tested for cognitive bias. The outcome measure was how many seconds it took the dogs to go to the ambiguous bowl after training as compared to before training.
Results
Dogs that had been trained in nosework approached the ambiguous bowl significantly faster than they did before whereas there was no difference for the dogs trained in heeling. The authors concluded that the dogs that were trained in nosework had a more “optimistic” outlook. They postulate that pet dogs generally cannot engage in natural behaviors such as foraging, which free-range dogs spend 10 to 22% of their time doing. They quote a number of studies that demonstrate that foraging is a natural behavior of many species including dogs and is a form of environmental enrichment important for animal welfare.
Conclusion
So how cool is this? Playing scenting games with our dogs, such as nosework, makes
their cognitive bias more positive. Future research will have to confirm the final
outcomes but if dogs are like other species, that more positive attitude will make them
more optimistic about life, increase their mental stability, improve how easily they learn
and remember, and improve their decision making.
Comments
OK, I know what you’re thinking – the dogs that were trained in nosework were clearly trained to look into boxes for food, so of course they went more quickly towards the ambiguous bowl in hopes of finding food. Well, it should be noted that the dogs in both groups were just as effective in identifying, and approaching or not, the positive and negative bowls during the cognitive bias testing – only their behavior towards the ambiguous bowl differed. That suggests that there wasn’t an effect of being trained to go and investigate bowls.
This study suggests that foraging (looking for and consuming food) is stimulating and intrinsically rewarding to dogs. Thus, increasing your dog’s foraging time, whether that means teaching nosework or scent work formally or just as a game to play around the house and yard, or using food-distributing toys might actually increase your dog’s optimism and outlook toward life.
And just as an extra note: oxytocin has been found to improve cognitive bias in dogs too (8). So all that time you spend petting, making eye contact, and telling your dog you love him/her (which has been shown to induce secretion of oxytocin in both human and dog) – that’s improving both your AND your dog’s outlook on life! I’m all for that
References
1. Harding EJ, Paul ES, Mendl M. Cognitive bias and affective state. Nature 2004;427:312. Read the PDF
2. Doyle RE, Fisher A, Hinch GN, Biossy A, Lee C. Release from restraint generates a positive judgment bias in sheep. Appl Anim Behav Sci 2010;122:28-34. Read the PDF
3. Asher L, Friel M, Griffin K, Collins LM. Mood and personality interact to determine cognitive biases in pigs. Biology Letters 2016;12:20160402. Read the PDF
4. Bateson M, Desire S, Gartside SE, Wright GA. Agitated honeybees exhibit pessimistic cognitive biases. Current Biology 2011;21(12):1070-1073. Read the PDF
5. Bethell EJ. A “how-to” guide for designing judgment bias studies to assess captive animal welfare. J Appl Anim Wel Sci 2015;18(sup1):S18-S42. Read the PDF
6. Barnard S, Wells DL, Milligan ADS, Arnott G, Hepper PG. Personality traits affecting judgement bias task performance in dogs (Canis familiaris). Nature 2018;8:6660. Read the PDF
7. Duranton C, Horowitz A. Let me sniff! Nosework induces positive judgment bias in pet dogs. Appl Anim Behav Sci 2018;Dec. 3. Read the PDF
8. Kis A, Hernadi A, Kanizsar O, Gacsi M, Topal J. Oxytocin induces positive expectations about ambivalent stimuli (cognitive bias) in dogs. Hormone Behav 2015;69:1-7. Read the PDF
2. Doyle RE, Fisher A, Hinch GN, Biossy A, Lee C. Release from restraint generates a positive judgment bias in sheep. Appl Anim Behav Sci 2010;122:28-34. Read the PDF
3. Asher L, Friel M, Griffin K, Collins LM. Mood and personality interact to determine cognitive biases in pigs. Biology Letters 2016;12:20160402. Read the PDF
4. Bateson M, Desire S, Gartside SE, Wright GA. Agitated honeybees exhibit pessimistic cognitive biases. Current Biology 2011;21(12):1070-1073. Read the PDF
5. Bethell EJ. A “how-to” guide for designing judgment bias studies to assess captive animal welfare. J Appl Anim Wel Sci 2015;18(sup1):S18-S42. Read the PDF
6. Barnard S, Wells DL, Milligan ADS, Arnott G, Hepper PG. Personality traits affecting judgement bias task performance in dogs (Canis familiaris). Nature 2018;8:6660. Read the PDF
7. Duranton C, Horowitz A. Let me sniff! Nosework induces positive judgment bias in pet dogs. Appl Anim Behav Sci 2018;Dec. 3. Read the PDF
8. Kis A, Hernadi A, Kanizsar O, Gacsi M, Topal J. Oxytocin induces positive expectations about ambivalent stimuli (cognitive bias) in dogs. Hormone Behav 2015;69:1-7. Read the PDF
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