Ask the Vet with Dr. Mike Davis 1/19-1/31

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Re: Ask the Vet with Dr. Mike Davis 1/19-1/31

Postby Leaddog » Tue Jan 18, 2011 7:14 pm

One additional note: a known shortcoming of mine is that I don't readily recognize when I am speaking gibberish to people. 99% of my person-to-person communication is with other research exercise physiologists, and I don't have a good handle on what is common knowledge. So if I write something that you don't really understand, point it out. Chances are very good you are not the only one I lost.
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Re: Ask the Vet with Dr. Mike Davis 1/19-1/31

Postby flowerpower » Tue Jan 18, 2011 9:48 pm

I'm hanging in there...but a couple of sub-questions-
What happens to the mitochondrial density in humans if they quit taking quercertin? Does it return to pre-supplement levels?
and do "winning" dogs-those that make the very best long distance racers-have more mitochondrial density than the house hound laying on my couch?

And along with Cindys Q&A-I understand getting rid of wastes-but I thought critters were also limited by lactic acid build up in the cells, which is a side effect of burning glucose. If I understand it very simply-lactic acid build up occurs when the blood cannot supply enough oxygen to the mitochondria to convert pyruvic acid(from burning glucose) to ATP. When oxygen levels return to normal, the lactic acid can than be utilized. So do sled dogs avoid lactic acid build up because they have more oxygen available in their bloodstream? Or am I totally confused? :oops:

PS-I agree, Austin is WAY too crowded. I moved here in 1980 from San Angleo and remember the good ole days of the Armadillo World HQ, Grateful Dead concerts at the race track, and Soap Creek Saloon-and thinking how big it was then!
"No matter how little money and how few possesions you own, having a dog makes you rich." - Louis Sabin
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Re: Ask the Vet with Dr. Mike Davis 1/19-1/31

Postby Leaddog » Wed Jan 19, 2011 6:08 am

To the best of my knowledge, no one has looked to see what happens when humans stop taking quercetin. My bet would be that they gradually return to pre-supplement levels.
Similarly, no one has looked that closely at linking race performance to mitochondrial density in any species. The outcome of the race is due to so many factors (+/- mitochondrial density) that it would require a massive study - hundreds of subjects all getting muscle biopsies. I don't foresee it happening in any species.
You are correct - if you burn glucose without supplying enough oxygen, you get lactate. We have never measured an increase in blood lactate in an endurance-trained racing sled dog, even after prolonged or maximal exercise. This means one of two things: they are either not producing it, or they are able to effectively store or reconvert it as fast as they make it. Not sure which, could be both. It is important to remember that the dogs are first and foremost fat burners and the gas collection studies so far support the idea that even at maximal exercise, they are burning fat proportionately much more than other animals at the same relative exercise intensity. So it is quite possible that their lactate production is very minimal.
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Re: Ask the Vet with Dr. Mike Davis 1/19-1/31

Postby emwcee » Wed Jan 19, 2011 2:22 pm

Hi Dr. Mike. Thanks so much for spending time with us. I have a couple of questions about the dogs' diets while racing a long-distance race. How many calories do they consume each day? And what would that be in human terms? Also, what percentage of their diet is fat during the race? How does their calorie and fat consumption compare to a normal training day? How does it compare to a normal house dog of similar size?
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Re: Ask the Vet with Dr. Mike Davis 1/19-1/31

Postby Leaddog » Wed Jan 19, 2011 3:10 pm

Calorie burn depends on the distance. In rough numbers, the dogs require about 2000 cal/day to simply exist. Regular household dogs need a bit less because they are not having to maintain body temperature in the cold and they don't have as much muscle (muscle maintenance is energy-intensive, even when you are not using them). Over and above that, figure about 60 calories/mile for the average-sized dog, regardless of whether it is racing or training. The dogs are not toting around a bunch of reserve for the same reason you don't see triathletes or competitive cyclists with excess body fat or really bulky muscle - it is simply weight that needs to be moved. The downside, though, is that there is always the possibility of an interruption in the caloric intake, so SOME reserve is needed to keep from lingering too close to the edge of the proverbial cliff. Factor in the distances between drop bags in the average race, and you can see that they must walk a fine line.
Calories are calories, regardless of the species, but to put it into perspective, the average Tour de France cyclist burns about 8000-9000 calories per day, but weighs 3 times the average sled dog.
The percentage of the diet that is fat is going to vary widely between mushers, and even between days for a single musher, depending on what is being fed. On a caloric basis, the diets tend to be in the neighborhood of 60% of the calories from fat. Certain snacks (like pure rendered fat) can be higher, others (like salmon) are lower. Fat is sort of the universal source of fuel the same way certain blood types are universal donors - just about anything we eat (fat, carbs, protein) can be turned into fat by our livers. The reverse is not true, though. The primary advantages of directly feeding fat are: if that is what they are going to burn anyway, it is more efficient and less stress on the liver; it is the most dense form of energy, so you can get it into the dog in large caloric amounts without overfilling the dogs's stomach; and it is very palatable so that even if the dog is tired and in a bad mood, they will eat it. The downside is that SOME protein and carb are required, and the diets that are very high in fat tend to have problems with storage (getting rancid, getting slimy, kibble breaking down into paste).
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Re: Ask the Vet with Dr. Mike Davis 1/19-1/31

Postby Breeze » Wed Jan 19, 2011 4:23 pm

Thank you so very much Dr Mike for meeting with us and being available in this forum. It is a joy and a pleasure to have you here .

You have sporting dogs as your own. I've had only sporting dogs ( setters and setter x 'trievers) in this family. I've seen some scary task -driven and task- orientation in my dogs... to go go go go go as long as their task is open they won't stop until the task is well finished on their terms, or < I > become the boogie man to call the task done/over and finished on my terms.

Are sled-dogs truly different in psychology?

Breeze/ Sue in Maine
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Re: Ask the Vet with Dr. Mike Davis 1/19-1/31

Postby Leaddog » Wed Jan 19, 2011 5:15 pm

Hi Sue. No, I don't think sled dogs are terribly different in psychology. If they are enjoying it, they will keep going, period. All that is different is precisely what they enjoy. My older dog will, without hesitation, retrieve until he falls over and starts having seizures (once) or I call it quits (all the other times over the last 10 years). We've sort of arrived at an agreement that when he comes back head-bobbing lame from an exaggerated dive for the ball, it is over for the day. He is also quite critical of my performance. A couple of bad throws or kicks (depending on what we are retrieving) and I start getting THOSE LOOKS from him. Even worse is his behavior while hunting. If Kathy (my wife) is not hitting anything, he will pointedly go sit next to whoever is hitting them so he can have something to retrieve (the ultimate diss, from our own dog no less).
Let's face it - we see precisely the same behavior in sled dogs, from the banging in harness until they injure their shoulders to the continued pulling even when they are out of gas or injured or sick; from the excited spinning when the gangline gets streched out before they start hooking up for a training run to THOSE LOOKS when the musher does something like falling off the sled. When sled dogs are enjoying what they do, we're the ones that have to stop them because they will not stop themselves even if they need to stop.
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Re: Ask the Vet with Dr. Mike Davis 1/19-1/31

Postby Heidi » Thu Jan 20, 2011 12:35 pm

Thanks for joining us Dr. Mike! I'm a fellow Texan (by way of the midwest, LOL). I've lived in Houston and Galveston (during hurricane Rita but pre-hurricane Ike) and now find myself deep in southwest Texas. I was happy to see that you went to veterinary school at Texas A&M!

I've really enjoyed reading about all your research...and about your background too! :) I found it interesting and inspiring that you knew at such a young age what you wanted to do and how you made sure everything you did from high school to finishing your degree was geared towards your goal of becoming a veterinarian - even if it meant doing the dirtiest of jobs for 9 hours in return for one hour of doing what you wanted to be doing.

So will you be attending both the 2011 Yukon Quest and Iditarod, and if so, what activities and research do you have planned?
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Re: Ask the Vet with Dr. Mike Davis 1/19-1/31

Postby JeanieB » Thu Jan 20, 2011 2:17 pm

Thanks for joining us, Dr. Mike,

I am reading about your research with much interest. A lot is above my head, but you are doing a great job of educating me in terms I can understand. Thanks for that!

I am wondering how many years you have worked/reasearched/volunteered for the Yukon Quest and Iditarod, and how much of your travel is paid for by you, by your University/research grant, and/or by Iditarod committe or individual mushers or sponsors. It must be very excensive, and I've always wondered how that works. I'm so glad someone is able to do this valuable work.

Also, being from Texas, what got you interested in sled dogs?

Mush on!
Jeanie B (from Virginia - so wonder why I asked that -teehee)
"When women reach a certain age, they begin to collect dogs. This is known as "Many - Paws""
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Re: Ask the Vet with Dr. Mike Davis 1/19-1/31

Postby Leaddog » Thu Jan 20, 2011 3:05 pm

Hi Hiedi
The project slated for the Quest is to investigate the electrolyte balances in the dogs. A lot of different things have come together for this. First, we've found over and over again, even in the best kennels, that the dogs are not actually at peak fitness this late in the season when they start running the races. They are capable of gaining additional fitness if properly challenged. Unfortunately, that challenge winds up being the race. In a way, it is not surprising - it has always been said that the very best training is to simulate competition. From a practical standpoint, it is pretty tough to simulate 1000 miles in 9-10 days, but the mere fact that it is inconvenient for us doesn't negate the physiology. We've found over and over again that the dogs respond to these major races as if they are just another training run, and go through many of the same conditioning responses that they did earlier in the training season in response to lesser challenges. In this project, we want to see whether they go through a process of increasing their blood volume in order to improve their cardiovascular fitness. The method they (or any other athlete) uses is to temporarily reduce the amount urine they produce, and they do this by selectively conserving sodium. Unfortunately, the mechanism used causes loss of potassium, and as a result, athletes responding in this manner go through a period in which they are relatively potassium-deficient. In severe cases, this can interfere with how muscle and nerves work, resulting potentially in muscle weakness, cramps, and twitchiness. I suspect that we will see this pattern in the dogs running the Quest - they will start out normal, they will be dumping potassium and conserving sodium during, and by the time they get to Fairbanks they will have re-established normal levels again. IF this is the case, it may provide some room for tweaking diets so that during a period when you know they will be dumping potassium, you can provide extra to help compensate.
The Iditarod project is an extension of the metabolism work. The process by which the dogs move fats and carbs into the muscle while it is contracting is very similar to the same net process that occurs after eating - the latter being driven by the hormone insulin instead of the contraction. We will be measuring the sensitivity of the body to insulin with respect to both clearing carbs and clearing fat from the blood stream before and after the race. I expect both sensitivities to go up as a result of the race, but I expect the ability to clear fat will go up more - indicating that the dogs are fine-tuning the overall system to rely more and more on fat to fuel the muscle.
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