Wounds: Healing from the Inside Out

I love wounds. My love for wound care began when I was a brand new nurse working in the ICU. Wounds are challenging to care for. Despite many innovations, wounds can be difficult to heal. I like a challenge it seemed natural for me to find wound healing fascinating. I am always amazed by the body’s capacity to heal itself. But more than the challenge of wound healing, I enjoy the always-advancing treatment options in wound medicine. Wound treatment continues to look for more effective and efficient methods for wound healing.

In human medicine, we have sophisticated options for wound treatment.  These technologies are being utilized in vet medicine as well. Dogs do seem to have an upper hand on us humans–they are better a healing. Their bodies seem well prepared to deal with wounds and more resistant to infection. However, dogs can get some nasty wounds that need intervention.

Today I want to talk about topical agents that are most commonly used in wound treatment.  By now we have all heard of honey and sugardene dressings and antibiotic dressings but how do the work? How do these treatments advance wound healing and are there any other options to help wounds heal?

First, let’s talk about wounds. There are many different types of wounds but the pathophysiology is similar in all. The first stage of wound healing is the inflammatory stage. This is when inflammatory markers are attracted to the wound through vasodilation. These cells are working to stop the bleeding and rid the body of any infections. In the second stage of wound healing, collagen fibers are forming. These fibers need oxygen and vitamins to create granulation (new) tissue. A wound must have granulation before epithelialization or the connection of epithelial cells occurs. In the final phase of wound healing, the body continues to lay down college fibers, creating a scar.

02/07/17 prior to Zinc treatments
03/03/2017 after one month of zinc treatments

One key part of wound healing is oxygenation of tissue. Generally speaking oxygenation of our tissue comes from our blood via the arterial system. The same thing occurs in wounds. The goal of wound management is to dress the wound with a material that will aid in oxygenation. That seems easy enough but there is one problem, necrotic tissue. The necrotic or dead tissue is kryptonite for wound healing–sometimes this has to be manually removed or debrided. The goal of wound care is to select a dressing to cover the wound that will prevent tissue death, keep the wound bed moist, and support healing.

Now let’s talk about antimicrobial dressings. Antimicrobial dressings generally contain iodine.  Iodine prevents infection. Sugardene is a mixture of sugar and iodine and an example of this. While these agents prevent and treat infection, they do little to aid in re-epithelialization. Antimicrobial dressings would be great for an abscess or dirty wound. This dressing aids in healing by preventing infection.

Another popular dressing that has gained a lot of attention is Manuka honey. Manuka honey is a raw honey made by bees that pollinate the Manuka bush in New Zealand. This dressing is thought to both be antimicrobial and anti-inflammatory. There are some that reports that suggest wounds do heal faster with Manuka Honey than antibiotic mediums.  The use of honey as a wound dressing has been practiced for many years and considered an effective treatment. Honey is also cost effective.

The last dressing that I want to mention is Zinc. Zinc is not an antimicrobial it is a trace element found in the human body. Zinc is an antioxidant that helps with oxygenation of the wound bed. This increased oxygenation in the wound bed is thought to help with re-epithelialization, aiding in wound healing.

03/18/17 six weeks after zinc treatments

I have used all of these topicals for wounds at one time or another. I am a fan of zinc for pressure ulcers in Greyhounds. As you can see in these photos above, Zinc increased granulation tissue, allowing the wound bed to close.  Zinc was a game changer for us.

All of these dressings have their purpose. It is hard to compare them head to head as their properties are different, what might work for a large leg ulcer may not help a minor abrasion or infected wound.

Wounds are challenging. The points to remember when dealing with wounds is to keep the wound bed oxygenated by preventing/removing necrotic tissue—selecting the appropriate wound dressing is essential. When in doubt or if a wound is not healing see a soft tissue vet. I have been blown away by the knowledge of our soft tissue vet as well as their continued patience for wound healing.

In addition to using the best wound dressing for the wound at hand, ensure that your Greyhound is using an appropriate bed. If pressure ulcers are a concern make sure bony prominences cannot be felt on the underside of the bed, I am a huge fan of these beds to prevent pressure sores. Finally, ensure that your Greyhound is receiving the best nutrition possible as wounds heal from the inside out!

Here is a video of Jethro’s bandage change. I hope you all find it helpful. And yes, Jethro is a very good boy!

Broughton G 2nd, Janis JE, Attinger CE. Wound healing: an overview. Plast Reconstr Surg. 2006 Jun. 117(7 Suppl):1e-S-32e-S
Gupta, M., Mahajan, V. K., Mehta, K. S., & Chauhan, P. S. (2014). Zinc Therapy in Dermatology: A Review. Dermatology Research and Practice, 2014, 709152. http://doi.org/10.1155/2014/709152
Sood, A., Granick, M. S., & Tomaselli, N. L. (2014). Wound Dressings and Comparative Effectiveness Data. Advances in Wound Care, 3(8), 511–529. http://doi.org/10.1089/wound.2012.0401

 

Is my Greyhound Dumb?

Have you ever tried to get your Greyhound to pay attention to you and he simply continues with his activities as usual? I have and it is annoying.

As I have mentioned, Jethro is recovering from an epidural hematoma in his back and subsequent hemi-laminectomy. Most of the time Jethro is happy and willing to participate in his recovery; other times he is not interested and has more important things to do like lie in the sun and act like a statue.

Jethro is not stupid and Greyhounds are not stupid dogs but they are not biddable.

There is a reason why Greyhounds aren’t biddable. Let’s think about the history of the Greyhound and what our racing Greyhounds are currently trained to do. Greyhounds, by way of nature and nurture, are independent thinkers. They are able to chase after something catch it and return it. They are able to position themselves on a track and successfully outmaneuver seven other dogs. The path that the Greyhound must plan to be successful requires some thinking that is not driven by a human. There is more to our Greyhounds than just raw speed!

This skills associated with racing and coursing are somewhat learned but also bred into the Greyhound. Genetics play a huge role in the Greyhound’s ability race on an oval track or course. That is not to say that training does not impact the Greyhound’s learning, but he has to have the capacity to think independently first or use his instincts.

Greyhounds are actually rather smart dogs. However, their independence can really be frustrating and create a negative environment for training or rehabbing.

So how do we make our Greyhounds as successful in rehab or training? It starts with knowing your dog and having your head in the game, so to speak!

I am a high-strung person with a touch of OCD, so I don’t do chill very well. This can be difficult when training dogs. While rehabbing Jethro I found myself very frustrated with him at times because he was not doing what I wanted and I couldn’t check that set of exercises of the list for the day. I found myself dreading his PT sessions, and I could tell that he dreaded dealing with me. After a very unsuccessful morning of trying to do PT exercises and Jethro impersonating a Greyhound statue, I knew something had to change.

Guess what, folks?  I needed to change. In the process of not completing his exercises for the day, I was becoming very nervous thinking about the possible terrible outcomes that lack of PT could lead to. I was focused on getting him better but not on Jethro or what Jethro needed in a trainer. I was a deranged anxious lady that he wanted nothing to do with; I was not his calm collected owner.

Now I make sure he is doing something daily but that can vary from increasing the time he stands, the number of sit-stand reps, or going on a 15-minute walk with Darla and Sashi.

Knowing my dog and where he is in his recovery has been essential to his improvements. Knowing your dog and where they are from day to day is essential in any type of training not just physical therapy.

Getting to know your dog opens the door for biddability. We must understand that there is more to our Greyhounds than raw speed – that big stubborn dog also has a lot of brain power.

Greyhound Anatomy: Feet

If I were asked what is the most important physical attribute of a Greyhound, without a pause my answer would be feet.

Often times we take our feet for granted forgetting that they support and balance us throughout the day. Feet are essential, just about every action we do involves our feet. One of the most important features of a Greyhound is their ability to run. So it would make sense that a Greyhound must have good feet to run through terrain after a hare or chase a mechanical lure on a sand track. Greyhounds need an exceptional base for them to perform at their best.

If you have ever studied a dog foot, it is complex structurally. There are multiple small bones that make up the carpus (wrist), foot, and toes of the Greyhound. All of these tiny bones have a purpose and even a small fracture can cause issues. In addition to the multiple bones in the Greyhound’s foot there are also ligaments that attach bone to bone and tendons that attach the Greyhound’s muscle to bone. And remember the feet need to be well innervated with nerves, sending and delivering messages between the brain and foot. It is essential that the Greyhound have excellent proprioception or know where its feet are and how to move its feet to achieve a task.

I believe that some dogs are born with superior feet. When considering breeding Greyhounds you have to weight out the pros and cons of both parents.  I am sure feet are considered as a toe or wrist injury can put a dog out of work for weeks to months. I grew up in Appalachia and one old wives tale was that a double dew clawed (dew claws on both the front and back feet) dog was a lucky dog. Dog people have always paid attention to dog’s feet.

I want to talk about a common injury that many Greyhound owners may encounter—a dislocated toe. A dislocated toe or luxation of the proximal interphalangeal joint (PIP) or distal interphalangeal joint (DIP) joint occurs when the ligaments that hold either the PIP or DIP  joints together can no longer tolerate the external stress on the joint and they give out. Generally speaking the joint will dislocate dorsally or upward. Oftentimes the joint will pop out of place and the ligaments still having integrity, will pull the luxated portion of the toe back into place. The toe will appear very swollen and sometimes will have a knife like cut where the luxation caused a break in the skin. However, the ligaments can completely lose their integrity and the joint will be displaced. Generally the Greyhound will be lame and you will be able to see the displaced toe. Often times the joint can be reset but this can be painful—I highly recommend against doing this on your own the first time unless you have experience resetting joints. In most cases with either presentation, the likelihood of the luxation recurring is high.

In addition to recurrence being high, successful treatment can be difficult to achieve as well. A trip to the vet is indicated to get an x-ray and make sure there is not a small fracture. For most pet owners the toe can be set and splinted for a week then rested for 2-4 weeks. Then pray the next time your Greyhound runs that the toe will stay in place!

Often times performance Greyhound owners will opt for intervention. Evidence for these types of procedures is variable. But certain orthopedic vets will complete the procedure and they can be very successful. Jethro severely dislocated his toe in March 2014, had stabilization with suture material in March 2014, and he continued amateur-running sports until December 2015 without any toe issues. If you were going to proceed with an intervention the vet would place a suture material or sclerotic material in the affected area to stabilize the joint then hope that the Greyhound’s inflammatory response will create arthritic changes to further stabilize the joint. If this fails amputation would be a reasonable next choice, especially for a non-weight bearing toe.

On the subject of amputation, I am not a fan or removing parts of the body that are not causing issues; however, as soon as trouble strikes and reasonable treatments have failed, remove the problem. Dogs don’t care about how many toes they have but they do care about pain!

There are also plenty of alternative methods to try in these cases. I am a believer in acupuncture, turmeric, and fatty acids (Omega QD). Some people really like a cold laser as well. I have used the cold laser many times and I feel that it does not hurt but I have not seen as much improvement with cold laser as other alternative treatments.

Greyhound feet are vital to our dog’s daily doings. Understanding the foot and where possible issues could arise is important so that you will be better prepared when an accident strikes.

The Fovea has it

Science really gets me excited.  What is most exciting is when something new is discovered.  This could be a new treatment, new technology, or revisiting of a previously thought notion or idea.

Eyes are one of the coolest organs in the body.  They are windows to the brain and some would say to the soul.  In humans the vital sign of the eye is visual acuity—you know, when you have to cover one eye and read the eye chart.  20/20 vision means that you see the same as a normal eye would see at 20 feet.  20/100 vision means that you see what a normal eye would see at 100 feet.  As you might imagine it’s much more difficult to test the visual acuity of a dog’s eye—they can’t tell us what they see.  Due to this, some scientists believe that the visual acuity of the dog has been underestimated.

We know that dogs see differently than humans do.  For many years we have known that dogs can see much better in low light than us; they have rapid vision that allows them to detect rapid changes in the light, and, due to the placement of their eyes in their skulls, they have wider visual fields than we do (Miller & Murphy, 1995).

All of these qualities aid the dog, a predator, in its ability to hunt.  However, the acuity at which the dog can focus was thought to be diminished, as the dog is known to lack a fovea (Miller & Murphy, 1995).  Fovea centralis (fovea) is a structure in the human eye.  The fovea is a depression within the retina that contains a large number of densely packed cones type cells that are responsible for visual acuity (Beltran et al., 2014).

For years scientists have felt that the dog’s visual streak was responsible for their visual acuity.  The visual streak is an area in the retina with increased amounts of photosensitive retinal ganglionic cells and cone cells (Miller & Murphy, 1995).  However, in 2014 things changed.

In 2014 the canine retina was evaluated with in vivo (in life) and ex vivo (in death) imaging (Beltran et al., 2014).  The researchers found an area in the retina very similar to a non-human primate fovea, which they deemed the area centralis.  This area was tiny but full of densely packed cone cells (Beltran et al., 2014).  This area was not a fovea-like depression but was very similar from a histologic standpoint to what is seen in the center of the human fovea, the foveola (Beltran et al., 2014).

You may be asking why is she so excited about this? This information is incredibly important.  This indicates that a dog’s visual acuity is actually better than previously thought.  The visual acuity of a dog was thought to be about 20/50 (Miller & Murphy, 1995).  Based on the findings in this study, the visual acuity of the dog would be between 20/24 and 20/13 (Beltran et al., 2014).  That means that dogs could be able to see at 20 feet what a normal eye would see at 13 feet!

The canine eye is an important structure for multiple reasons.  For our Greyhounds the eye is important for racing, lure coursing, coursing, hunting, fetching, running through agility obstacles, and their everyday lives.  Just imagine having better than perfect vision and then adding a wider visual field, the ability to detect rapid changes in light, and the ability to see in low light—I would be overwhelmed with that much stimuli going through my brain all the time!  Dogs are complex animals and the more we learn about them the more I amazed by all they do!

Beltran, W. A., Cideciyan, A. V., Guziewicz, K. E., Iwabe, S., Swider, M., Scott, E. M., Aguirre, G. D. (2014). Canine retina has a primate fovea-like bouquet of cone photoreceptors which is affected by inherited macular degenerations. PLoS One, 9(3), e90390. doi:10.1371/journal.pone.0090390
Miller, P. E., & Murphy, C. J. (1995). Vision in dogs. J Am Vet Med Assoc, 207(12), 1623-1634.

 

 

Greyhound Nails

One of the best parts of greyhound ownership is the lack of grooming they require.  Greyhounds are wash and wear dogs.  They do not need a lot of brushing, trimming, or bathing.  However, their nails do need some attention.

First things first, what is a nail?  The nail is protective covering of the bones and vessels under the tip of the foot.  Nails are made up of a strong fibrous protein called keratin.  This protein is also found in skin and hair.  Nails protect the tip of the foot from damage and help with gripping while running.  

 

 

So what happens if your greyhound’s nails are too long?  Well, multiple issues can occur.  The most concerning issues are the changes to the gait associated with long nails.  When the nail is touching the ground this puts pressure on the bones of the foot.

Remember the old saying about greyhounds? “A greyhound should be headed like a snake and necked like a drake, backed like a beam, sided like a bream, footed like a cat and tailed like a rat”.  This poem should be taken to heart when thinking about the greyhound foot.  When the nails of the hound are too long it creates an uneven balance of pressure in the foot.  This pressure lengthens the ligaments in the foot causing the toes to appear longer and the dog to not walk properly.  This can also be painful.

Pressure sores or decubitus ulcers can also occur with overgrown nails.  The overgrown nails come in contact with the thin skin of the foot and can cause breakdown.  This can lead to infection and can be very painful to the dog.  Pressure sores are difficult to heal.  The offending agent or pressure has to be removed so that the wound can heal properly. 

You can see why nail care is important but what do you need to trim nails?  I recommend plier-style clippers with a safety stop.  I find that guillotine clippers are difficult to use.  Guillotine clippers do not give you the control of the scissor clipper.  It is also more difficult to see what you are doing while trimming the nails.  You should also buy septic powder.  This is good to have on hand in case you do nick the nail quick.  Remember to hold pressure to stop the bleeding as best as you can then apply this.  Septic powder works best on dry surfaces.  Grinding tools are also useful tools to have in your nail bag.  They can file the nail down and if you are worried about the quick there is no clipping involved.  I would recommend grinding nails outside and with a mask on and eye protection.  Also move the tool over the nail as it will heat up.  Continued pressure in one spot will heat the nail and can be painful to the greyhound. 

So you have your tools but how do you successful clip greyhound nail?  I understand that nail clipping can be scary.  We know all too well that there is a sensitive quick in the nail and clipping it can cause bleeding and pain for the dog.  Well friends, I have news for you.  If you look at your hound’s foot you can easily spot the quick even on black nails.  

Once you know where the quick is you make you first cut at about 45-60 degrees.  I recommend then making two additional cuts to the side of the nail to make sure you have removed all the overgrowth.  Once this is completed you can file the nail with an emery board or grinding tool.  A rule of thumb for nail length is that you should be able to slide a credit card under the dogs nail while standing   

Most retired racers are well accustomed to nail clipping as this was a regular part of their routine.  However, if your hound is not so cool with the idea of clippers coming close to their toes some positive reinforcement could help.  I find that using a plastic toy stuffed with food will keep a hound busy while clipping.  The clicker could also be used for this.  Creating a positive association with the clipper can be helpful with a lot of dogs.  Remember to channel your inner leader while nail clipping, dog can sense if you are not confident in your skills.  Getting you and your hound accustom to nail clipping can take some time but well worth the effort!

I hope that this has been helpful to you and you now ready to clip you hound’s nails with confidence!

Greyhound Teeth and Gums

 A few weeks ago I wrote an article on greyhound digestion.  We learned that greyhounds rely on the crushing power of their molars to break down food, as they lack the enzymes needed to begin carbohydrate break down in their mouths. 

Due to this, dogs’ teeth are important to their overall health.  Greyhounds are known for their bad teeth.  Today, I want to discuss the greyhound’s teeth and gums, how gingivitis occurs, and then how to get your greyhounds mouth into tip-top-shape!

If you have even been around a greyhound puppy, you know why they are called “land-sharks.  They have super fine sharp teeth that will cut through skin and bring you to your knees.  Thankfully at about six months these 28 extremely sharp weapons fall out and replaced by 42 permanent adult teeth.  Dogs have four types of teeth: canines, incisors, premolars, and molars.  The canines are responsible for ripping or tearing flesh and the molars are responsible for crushing.  These adult teeth lack in sharpness but are efficient at bringing down quarry and enable the greyhound to tear through bone and muscle. 

Just as the adult teeth need to be strong to function, they also depend on strong gums for support.  Gums are tissues in the mouth that are covered with oral mucosa.  Gums help keep the teeth aligned and supported.  If the gums are not healthy the teeth cannot be healthy either. 

So why do greyhounds have such “bad” teeth?  There are several hypotheses but no clear answer at this time.  The national greyhound adoption program (NGAP) blames this on a raw diet fed at the kennels; however, I disagree.  A raw diet with meaty bones should promote good dental care.  Some feel that there is a lack of concern about teeth in the greyhound industry and point out that there is only a half page on tooth care in the greyhound bible AKA Care of the Racing Greyhound: A Guide for Trainers, Breeders, and Veterinarians.   I am not sure that this is that accurate either, as tooth brushing is not difficult and could be covered quickly.  The cause of bad teeth could be debated all day and a clear answer may not surface.  Let move on to how tooth decay and gingivitis occur and how to prevent this.

Dogs have bacteria in their mouths, and certain bacteria are part of their normal flora (friendly bacteria).  They also get bacteria in their mouths from eating, licking, chewing, and doing dog things.  These bacteria stick to the teeth.  If these bacteria are not removed from the teeth they cause irritation to the gums.  This is called gingivitis.  Most likely your hounds have gingivitis if their gums bleed with brushing.  This is commonly seen early in an oral care program.  Regular teeth brushing and chewing can reverse this.  If these bacteria are not removed they will continue to build up on the teeth.  This build-up of bacteria (tarter) will weaken the enamel of the teeth causing decay.  This build-up of tarter can also affect the bone under the gum supporting the tooth if not removed.  Once the bones supporting the teeth are affected the dog has periodontitis.  This is not reversible and can cause tooth loss if not stopped.  

The importance of the teeth and gums are paramount.  Teeth not only support our nutritional needs, but if they are diseased, they create an entryway for bacterial to enter into the blood stream and potentially cause life-threatening infections.  

How do we prevent this from happening to our best friends?  Number one most important thing is brush their teeth.  I admit that I am not the best at daily brushing, but after writing about the horrors of periodontitis I can promise you there will be daily brushing in our house!  The second thing is to feed raw bones.  Raw bones are irritants to built-up tarter on the teeth.  The grinding of the bone helps to remove the tarter on the molars as you can see in the photo above.  Please, do not feed cooked bones, as they can be extremely harmful to dogs.  The cooking of bone denatures the proteins and causes splintering of the bone when chewing.  Finally, encourage chewing!  I love planet dog toys.  The Orbee-Tuff line holds up to my aggressive chewers and the toys have a nice peppermint scent to help with bad breath.  

I hope that this article is helpful to you and your hound.  Below is a video of how we brush teeth.  Promoting clean teeth and gums is one of the best things you can do for your greyhound!

 




 

Liver and Thyroid functions.

Today I am going to discuss liver function in greyhounds as well as thyroid function.

Let’s start with the liver.  The liver is an important organ in metabolism of food and drugs.  There are two main blood markers that we check for liver damage:  alanine aminotransferase (ALT) and aspartate aminotransferase (AST).  ALT is found in the liver and elevated levels are directly correlated with liver damage.  AST is found throughout the body in various cells.  AST can be elevated in hepatic injury but also for other reasons not related to the liver.

Greyhounds have elevated ALT without associated liver damage.  I was puzzled by this and could not find any data about why this would occur.   A genetic change is the most reasonable explanation of the greyhounds’ LTF abnormalities.  Again, selective breeding most likely caused this, and unlike the RBC changes that improve the greyhound’s athletic ability, this is just a side effect.

So if the greyhound has elevated ALT, is that why they cannot process drugs as quickly as non-greyhound dogs?  This is not the case.  In the livers of both humans and dogs there are enzymes called cytochrome P450 (CYP), and these are the liver’s metabolizers of drugs.  There are hundreds of these enzymes, all with different numbers.  Most if the information regarding this came from humans and has been used in dogs.  This area of study is booming and these researchers have found differences in this system between dogs and humans as well as between breeds.

Structure of the POR protein. Based on PyMOL rendering of PDB 1amo. Credit: Emw is licensed under CC-BY-SA 3.0

In particular the greyhounds CYP system is atypical from other dogs.  I am sure that you know greyhounds have issues with anesthesia and the anesthesia they receive should be different than other non-greyhound dogs.  This was originally thought to be from the lack of body fat in greyhounds.  This was found to be less likely after a series of studies looked at drug metabolism.  These studies found that if greyhounds were given a CYP inducer like phenobarbital, they could clear anesthesia agents more quickly; conversely, if a CYP inhibitor (chloramphenicol) was given prior to anesthesia, it would take longer for the drug to be cleared.  This points directly to the CYP system as the cause of delayed drug clearance and not the lack of body fat in the hound.

To sum it up, the changes in the liver enzymes seen in greyhounds does not cause the issues with drug metabolism in the greyhound.  However, the CPY system within the greyhound’s liver is unique and creates the changes in drug metabolism.

Now we have a better understanding of the liver function abnormalities seen in greyhounds, let’s talk about the thyroid valves.

There are four common thyroid tests completed when checking for disease in the thyroid.  They are total T4, free T4, T3, and thyroid stimulating hormone (TSH).  TSH is controlled by the pituitary gland in the brain; it controls the thyroid gland’s production of T3 and T4.  Thus, when TSH is elevated it means that there is not enough T4 or T3, and when the TSH is low it means that there is too much T4 or T3.  TSH and T3 play a large role in the diagnosis of hypothyroidism.  T3 is often more important in hyperthyroidism, as there is less of it made in the thyroid and oftentimes takes longer to become abnormal.

Greyhound’s T4 is oftentimes abnormally low; this has been well documented.  It is important to note that current racers or right-off-the-track retired racers have even lower T4 then non-racing greyhounds.

This posed the question about hypothyroidism in these dogs.  There was a study that gave greyhounds with low T4 synthetic thyroid stimulating hormone.  In a mammal with true hypothyroidism this should have elevated the T4, but this did not occur.

This furthered the idea that greyhounds have baseline low thyroid levels and prompted an additional study.  In this study a radioactive tracer was used to evaluate the thyroid function in greyhounds suspected of hypothyroidism.  The uptake of the tracer was within normal limits compared against dogs with normal thyroid function.  This indicated that hypothyroidism is extremely unlikely in greyhounds.

Greyhounds are different from other dogs for various reasons.  These variations in their lab values should be evaluated by someone who has experience with greyhounds.

I hope this series was helpful and you are more informed about why greyhounds’ lab valves are different from non-greyhound dogs.

 

Court, M. H. (2013). Canine cytochrome P450 (CYP) pharmacogenetics. The Veterinary Clinics of North America. Small Animal Practice43(5), 1027–1038. http://doi.org/10.1016/j.cvsm.2013.05.001
Zaldívar-López, S., Marín, L. M., Iazbik, M. C., Westendorf-Stingle, N., Hensley, S., & Couto, C. G. (2011). Clinical pathology of Greyhounds and other sighthounds. Veterinary Clinical Pathology / American Society for Veterinary Clinical Pathology40(4), 10.1111/j.1939–165X.2011.00360.x. http://doi.org/10.1111/j.1939-165X.2011.00360.x

WBCs and platelets in greyhounds

We discussed the differences in greyhound RBCs and non-greyhound RBCs.  There are two other types of blood cells that are different in greyhounds vs. non-greyhound dogs, the White Blood Cell (WBC) and the platelet. 

RBCs, WBCs, and platelets are made in the bone marrow.  After they are mature they are sent into the blood stream.  As discussed previously, the RBC carries oxygen to the tissues.  The WBC’s job is more complex; lets look at it first. 

WBCs are immune cells.  They fight off viral, bacterial, parasitic, and fungal infections.  This is an important job, and there are multiple cells types and they each specialize on a certain intruder. 

I am going to break down WBCs cells lines as simply as possible.  I want this to be easy to understand for everyone!  If there are any questions please comment or email and I will be happy to address this further. 

There are five main types of WBCs.  Some of them are granulated and have a nucleus or control center (RBCs do not have this).  These granulations are particularly important.  The granules are enzymes within the cell that improve cellular function—i.e. they are the marinade on the foreign evader the WBC is going to destroy.  These are the types of WBCs found in the body:

1.     Neutrophils: most numerous WBC.  Nucleated and have granules.  Responsible for ridding the body of bacterial and fungal infections.

2.     Eosinophils: nucleated with granules.  Responsible for ridding the body of parasites.  Assist in allergic reactions.  Help destroy cancer cells. 

3.     Basophils: nucleated with granules.  Basophils control the histamine response in inflammation.

4.     Lymphocytes: Multiple subsets (T and B cells) of the lymphocyte—complex cell with very important functions.  Some subsets have granules others do not.  All have nuclei.  Help the body rid itself of viral and bacterial invaders and also create memory cells so that when the same infection enters the body again, it will be prepared. 

5.     Monocytes: nucleated without granules.  They have longer lives than the other WBCs.  When mature they migrate to the tissues and organs and hang out there to take care of any potential bacterial evaders. 

With all of this complexity it is hard to believe the immune system does not go haywire more often!

Now lets look at the differences in greyhound labs values vs. non-greyhound dogs. Lower WBC counts are often seen in greyhounds.  This has been well defined and is currently not a point of concern, as it is considered a breed trait.  The eosinophil of the greyhound has been widely studied.  Beginning in the 1960s the greyhound was discovered to have a vacuolated eosinophil, meaning that the granules within the cell would not stain for microscopic examination (FYI staining is a method of putting a dye into cells allowing them to be better evaluated by microscope).  This was odd, as non-greyhound dogs’ eosinophils will stain orange with a quick stain method.  The lack of the staining was concerning, as it appeared to be a toxic cell.  The concern for abnormalities prompted large work-ups looking for a source of the inflammation.  Fortunately, these changes were not pathologic.  This prompted more studies.  In 2005, there was a study published in Veterinarian Clinical Pathology.  This study looked a 49 greyhound blood smears and compared them to 200 non-greyhound dog blood smears.  A more advanced staining method was used than in the 1960’s study.  This study showed that structurally and chemically, the greyhound’s eosinophil was the same as the non-greyhound dogs.  This suggests that there were different staining properties in the greyhound eosinophil but overall it was the same cell seen in non-greyhound dogs.  The cell was deemed not pathologic.

In addition to the changes in the WBC there are also changes in the platelet counts of greyhounds.  First things first, what is a platelet? Platelets are tiny blood cells that are made in the bone marrow with RBCs and WBCs.  They are responsible for blood clotting.  

Greyhounds are known to have low platelet levels.  This is considered to be a breed trait as long as the count is not below 100,000/μL.  Again, I ask why is the greyhound’s platelet different from non-greyhound dogs?  Well there are multiple theories about this.  The first came about in 1994 by PS Sullivan.  This theory has been supported multiple times since and focuses on stem cell competition.  Do you remember the RBCs we talked about a few days ago?  Well, Sullivan posited that when the bone marrow begins creating the building blocks of blood, there is a competition between the cells destined to be platelets and the cells destined to be RBCs.  Due to the need for more RBCs in the greyhound, the poor platelets lose this fight—leading to lower platelet counts.  Another theory focuses on the mature RBCs—due to the amount of oxygen molecules on the RBC, there is a mild loss of oxygen overall when the RBCs release the oxygen into the tissues, and this mild hypoxemia causes an increase in the production of RBCs, thus causing a decreased production of platelets—remember these cells are in competition.  Both of these studies show that the competition between the RBC and the platelet either in the blood or the bone marrow is most likely why greyhounds have lower platelet counts. 

Naturally one would think that greyhounds would be “easy bleeders” due to their low platelet counts.  Well, they are “easy bleeders” but it is not due to the lack of platelets.  Actually, the time it takes for a greyhound to create a platelet plug or the “closing time” is very similar to non-greyhound dogs.  This suggests that greyhounds’ platelets are more active than non-greyhound dogs.  These researchers also looked at the risk for bleeding disorders in greyhounds, but this was very rare and not related to their “easy bleeding” tendencies.  However, the clot strength in the greyhound was weaker than non-greyhound dogs—this most likely is the cause of the “easy bleeding” in greyhounds.  

So why would the greyhound be able to clot quickly with a low platelet count but then create a substandard clot? Aging that points back to the high level of RBCs in the blood.  Due to the high RBC mass in the blood, the plasma (fluid in the bloodstream after removal of RBCs, WBCs, and Platelets) has less Fibrinogen (a protein that aids in clotting).  This is the confusing part; there is actually no difference in the fibrinogen levels in greyhounds vs. non-greyhounds.  The mass of the RBCs within the blood is to blame for the pseudo hypofibrinogenemia.  Additionally, it is thought that greyhounds have enhanced fibrinolysis (the ability to break down clots).  This would keep the greyhound from clotting, as they are at risk due to the increased viscosity of blood during exercise. 

Photo Credit: Cindy Frezon

 To sum up the bleeding tendency of the greyhound goes something like this: greyhounds have low platelet numbers but active platelets and these platelets create clots quickly but the clots lack stability due to low levels of fibrinogen due to elevated RBCs in the blood.  Furthermore, is has been theorized that greyhounds have active fibrinolysis and can break up clots quicker than non-greyhound dogs. 

Whew! Now we have looked at the RBCs, WBCs, Platelets, and hemostasis in the greyhound.  It has been great for be to learn more about this.  I now have an understanding of why these levels are different from non-greyhound dogs and I think this adds to the undeniable coolness of the greyhound! The last series on labs will be next week and it will focus on liver and thyroid functions.  Hope you check it out!  

Iazbik MC, Couto CG. Morphologic characterization of specific granules in Greyhound eosinophils. Vet Clin Pathol. 2005; 34:140–143.
Feature image credit: Cindy Frezon
Sullivan PS, Evans HL, McDonald TP. Platelet concentration and hemoglobin function in greyhounds. J Am Vet Med Assoc. 1994; 205:838–841. [PubMed: 7829376]
Zaldívar-López, S., Marín, L. M., Iazbik, M. C., Westendorf-Stingle, N., Hensley, S., & Couto, C. G. (2011). Clinical pathology of Greyhounds and other sighthounds. Veterinary Clinical Pathology / American Society for Veterinary Clinical Pathology40(4), 10.1111/j.1939–165X.2011.00360.x. http://doi.org/10.1111/j.1939-165X.2011.00360.x

What is up with lab values and Greyhounds?

Like I have said previously, I am a nurse and a researcher.  I like to figure out why things do what they do.  When I got Jethro I was amazed by the difference in laboratory (lab) valves in greyhounds and non-greyhound dogs. 

I searched the Internet looking for studies to show why the difference existed.  I recently found a literature review that does a good job with this but it is very science driven and not accessible to most greyhound owners.

Due to the numerous differences in the greyhound and non-greyhound labs, I am going to do a lab series on the blog looking into the different abnormalities. 

Today I am going to dive into the red blood cell values of the greyhound.

First, let’s talk about the red blood cell (RBC) or erythrocyte.  The RCB is the most common cell in the body.  It is disc-like cell that looks like a jelly doughnut with the jelly squeezed out.  RBCs are important because they house hemoglobin (Hgb), which carries oxygen to the body.  Hemoglobin is a protein within the RBC.  The hemoglobin molecule accepts oxygen from the lungs and carries it throughout the body, bringing nutrient rich blood to our organs.  The hematocrit (Hct) is a measurement of the volume of RBCs in the body—this value is needed to get an accurate hemoglobin measurement.  There are two additional RBC values that are different in non-greyhounds and greyhounds.  They are the Mean corpuscular volume (MCV) and the Mean corpuscular hemoglobin (MCH).  The MCV measures the size of the RBC and the MCH measures the color of the cell. 

Adult blood smear by scooterdmu

That is very basic RBC science.  Let’s now talk about the abnormalities in the greyhound’s valves and what they could mean.  Greyhounds have higher RBC counts.  The higher RBC cases an increase in Hgb concentrations and Hct.  These higher values allow for oxygen to reached stressed muscle cells quicker.  Initially selective breeding, training, and racing were deemed the cause of these changes; however, there are additional studies looking at other possible causes.

An argument against training and racing as a cause for these changes was completed looking at Hemoglobin and Hematocrit values in 5-6 month greyhounds and 9-10 month greyhounds.  This study showed that at 5-6 month the greyhound Hbg and Hct were not much different from non-greyhound dogs and much lower than the greyhounds in the 9-10 months group.  They then looked at the 9-10 month group vs. 12-13 month greyhounds. The differences in Hgb and Hct at 9-10 months vs. 12-13 months were statically insignificant, suggesting that at 9-10 months greyhounds have adult lab valves.

Sashi at 6 months by Cindy Frezon

On the other hand, there are studies to suggest that selective breeding is the cause for these changes.  The hemoglobin molecule in the greyhound has a higher affinity for binding to oxygen.  These studies also found unique amino acids mutations on the Hgb to allow for enhanced oxygen-binding capacity. 

You may be asking, how would breeders know this and know which greyhounds to breed?  Most likely the early dogmen breed greyhounds to be hearty, fast, and recovery quickly to hunt again whenever new quarry was seen.  This need for fast recovery influenced breeding practices, meaning that these hounds that were able to recover quickly again had higher RBC counts and more efficient hemoglobin.  These factors are still considered in breeding programs today – talk to any dogman or woman and they will tell you that test-mating or selecting a breeding pair is a time-consuming task with lots of consideration.  

Darla at the Christmas Cup 2015 by Cindy Frezon

Another interesting fact about greyhound RBC valves is the lives of their RBCs.  In non-greyhound dogs, the life of the RBC is around 100 days.  In Greyhounds the life of the RBC is about 50 days.  There are multiple theories about why this is.  Some believe that greyhounds trap their RBCs in their spleen; however, there is no proof to this theory.  Another theory is that the greyhound’s immune system selectively rids its self of older cells, but again this needs to be studied further for more clarity. 

Greyhound’s blood counts also show elevated MCV or large RBCs.  This was thought to be related to elevated reticulocytes (immature RBCs) in the blood but that is not the case. The increased size is breed specific and most likely due to the higher hemoglobin content within the RBC.  This would allow for more oxygen to reach the muscles and allow for continued activity. 

I hope that after this review you have a better understand of the RBC and why it is different in the greyhound.  As I had said before greyhounds are special dogs that do special things.  I think it is fitting that their labs are special too!  Check in later this week for differences in WBCs and Platelets in greyhounds.

 
Feature Photo Credit: Cindy Frezon
Zaldívar-López, S., Marín, L. M., Iazbik, M. C., Westendorf-Stingle, N., Hensley, S., & Couto, C. G. (2011). Clinical pathology of Greyhounds and other sighthounds. Veterinary Clinical Pathology / American Society for Veterinary Clinical Pathology40(4), 10.1111/j.1939–165X.2011.00360.x. http://doi.org/10.1111/j.1939-165X.2011.00360.x

Dog digestion and feeding

Dog GI system

After writing my myths BUSTED post, I began thinking about how often I am asked about what I feed my greys. I felt that this topic is worth spending more time discussing.

 First let’s discuss the gut of a dog. All mammal digestion begins in the mouth. This is where we begin to break down the particles in our food to extract the important elements needed for sustained life. Most mammals produce amylase, an enzyme that breaks down carbohydrates, in their saliva. Amylase is not produced in a dog’s saliva.

We must remember that our sweet cuddly greyhounds are natural born predators that are more than able to crush through bone and muscle meat with ease. Carbs were not often on the menu.  Open up her mouth and check out those huge teeth!

After reading this about amylase I was confused as to how dogs break down kibble. Let’s dive into the dog’s GI tract to learn how this happens.

After your hound ravenously devours her food, she swallows it. The esophagus allows the passage of food from the mouth to the stomach. The esophagus is just a connection, nothing exciting happens here.

Then the food enters the stomach. Dogs have single chamber stomachs like humans. The stomach pH of a dog is about 2, which is the same acidity as lemon juice.  The strong gastric acid combined with the muscle strength of the stomach begins to break down food into absorbable molecules- but minimal absorption actually occurs in the stomach.

© Hill’s Pet Nutrition, Inc.
© Hill’s Pet Nutrition, Inc.

 

Once the food has been broken down by the gastric acid, the food enters the small intestine. Mammals have three parts that make up their small intestine: the duodenum, jejunum, and the ileum. The small intestine is a large organ and can be about two and half times the dogs total body length!

© Hill’s Pet Nutrition, Inc.

The duodenum is the smallest part of the small intestine but the most important. The duodenum connects the small intestine to the stomach. While food is in this section it is combined with enzymes from the gallbladder, pancreas, and liver. The duodenum is where amylase, lipase, and proteinase begin to break down carbohydrates, fats, and protein, creating the building block for life.  In the duodenum, kibble is broken down.

After the food is further broken down, it enters the jejunum. The jejunum is the longest section of the small intestine. The jejunum has a large surface area to allow for absorption of nutrients.

After the jejunum successfully absorbs all important nutrients from the food, the remaining intestinal contents are released into the ileum. The ileum connects the small intestine to the large intestine.

Once the intestinal contents reach the large intestine most nutrients have been absorbed and broken down. The job of the large intestine is to absorb water and create feces. The large intestine is critically important in the hydration status of the dog. Once most water is absorbed, the feces enters the anus and then rectum. Once in the rectum the dog will be able to expel its waste.

© Hill’s Pet Nutrition, Inc.

Dogs have quick digestive systems and depending on your fed, digestion can take them 6-12 hours per meal.

Feeding

 Now we have a basic understanding of how a dog’s gut works. Let’s talk about what to feed your greyhound.

 

When I first read that dogs do not have amylase in their mouth I felt that raw food was the only way to feed a dog.  Since learning more about dog digestion and monitoring my dogs on raw my opinion has somewhat changed.

I have three greyhounds. They were fed raw for about three years. I have followed both the BARF (bones and raw food) method and whole prey.  I feel that whole prey worked better for my dogs and aligned with my concerns regarding no amylase in dog saliva. I used multiple protein sources and felt very good about the diet they were receiving.





However, Jethro never thrived on raw. His coat was dull, thinning, and he was very skinny (even for a greyhound). I tried to increase his rations but he began to refuse to eat. After about 10-14 days of him barely touching his food I knew something had to change.

 


I started him back on a very high quality kibble. Seriously, his eyes about popped out of his head when he saw a bowl full of kibble. I realized that raw was not for him. He did not do well on it.

 

I do still give him raw bones to help with tarter build up.


 

After my experience with Jethro I wanted to learn why greyhound trainers would feed kibble and raw together. After all, this goes completely against everything I had learned about the horrors of feeding raw and kibble at the same time.

 

I researched this more, reading accounts on what Henry VIII fed his hunting greyhounds, what open field coursing greyhounds are fed, and what top US racing greyhounds eat.  A theory for feeding carbohydrates continued to surface throughout my research; it stated that greyhounds need a lot of ready-to-use energy for sprinting. The carbohydrates in kibble, pasta, and rice that trainers often feed help with this. The balance between the raw protein source and the kibble create a balanced diet for quick acceleration from an energy standpoint.

I encourage greyhound owners to try different diets and see what their hound thrives on. There are easy options for raw and kibble. The most important thing to remember when choosing a food it how you dog looks, feels, and preforms on that diet.  After all a dog’s diet is not a bragging point between humans but an elemental point of existence for your hound.

The illustrations in this post are reprinted with permission by the copyright owner, Hill’s Pet Nutrition, from the Atlas of Veterinary Clinical Anatomy. These illustrations should not be downloaded, printed or copied except for personal, non-commercial use.