Super-fit Iditarod dogs may be as famous as the human mushers who accompany them to the finish line in Nome – and even more accomplished. One given name is enough for these incredible dogs, but like LeBron and Magic, the most famed become household names like Granite, Maple and Zorro, lead dogs that follow in the footsteps of the legendary Balto. These elite animal athletes possess physical traits that allow them to race across Alaska in less than nine days.
As veterinarians work to keep the dogs healthy, they are also on a mission to unlock scientific mysteries behind the animals' unique capabilities. As a result of those efforts, fewer Iditarod dogs are dying, canine soldiers are better prepared for war, and some scientists believe the dogs' phenomenal metabolism may hold a key to combating some human diseases.
Here's what sets these animals apart.
Massively more capable than the best human athlete
"With a human you may be looking at months and months of meticulous training to reach peak fitness. Dogs can achieve a far greater level of fitness much more rapidly. It's not just what they are capable of doing, but how fast they can bring that on line," said Michael Davis, a veterinarian from Oklahoma State University who has studied Iditarod dogs for years.
Iditarod dogs are ultramarathoners, with the fastest among them running nearly 1,000 miles in a little more than a week. They go and go and go, fueled by an amazing number of calories. Racing dogs may eat as many as 12,000 calories a day, the equivalent of about 22 Big Macs from McDonald's.
When you consider that an average racing dog weighs 50 to 60 pounds, maybe a quarter the size of some human athletes, the calorie intake and stamina are even more impressive.
"The dogs are just massively more capable than the best human athlete," Davis said. "We can be pretty safe in saying they are the best domestic animal athletes."
No hummingbirds
But there are critters in the animal kingdom that will even surpass sled dogs.
Compare dogs' aerobic capacity to other animals, and you get a sense of just how capable the dogs are.
"In all those cases, the dogs beat the best race horses when you compare them pound for pound," Davis said.
What critter tops a sled dog's aerobic ability? The hummingbird is one. Hummingbirds possess the "highest known mass specific metabolic rates known in the vertebrate world," according to the website www.science20.com.
"Hummingbirds are very, very highly aerobic. They are far in excess of what a sled dog can do," Davis said. Antelopes may be another. But Davis suspects the aerobic performance of highly trained sled dogs may ultimately beat out gazelles, impalas and the other hooved endurance runners of the African savannah.
Dog care: 'A people thing'
Advances in how the four-legged Iditarod athletes are cared for before and during the race have lessened injuries and deaths.
In the 1990s, veterinarians began conducting pre-race EKGs and blood work on the dogs, looking for abnormalities that could prove problematic. Dogs that don't pass the tests cannot race. Abnormalities aren't the only thing vets look for but differences in health profiles among all the dogs on a team can be crucial. An otherwise healthy dog whose body performs differently than its teammates' may need to be watched more closely, explains Stuart Nelson, who's back for his 20th year as the Iditarod's chief veterinarian.
One of the most significant medical breakthroughs, though, has been the addition of Prilosec, an over-the-counter antacid, as a routine supplement to prevent gastric ulcers in dogs.
Quietly and with no outward signs, ulcers can wreak havoc with hard-running dogs. Chronic slow bleeding, an acute onset of major bleeding and vomiting that leads to choking all can be fatal side effects of this otherwise silent condition. Davis made the discovery about the prevalence of ulcers in racing dogs after 10 years of performing exams on dogs running the Iditarod and other races. Davis' prior studies have shown that exercise-induced stomach disease may affect 50 percent to 70 percent of the dogs that enter the race, a number far higher than is seen in non-racing dogs. Those that develop the condition are at risk of developing ulcers, a more serious progression of the illness.
Since there was no way to easily detect an ulcer's presence, hindering treatment during the race, prevention was key. Before long, a gastric acid suppressant sold under the brand name Prilosec was added to the dogs' daily race routines. Around 2009, researchers found the medicine worked even better on an empty stomach, something Nelson calls the "most dramatic" breakthrough for medical research on racing dogs in recent years. Even better, it delivered instant results.
After six dogs perished in the 2009 Iditarod, no dogs died on the trail the next year, a breakthrough that was repeated in 2011 and 2012. In 2013, a dropped dog, tethered and sheltered behind a building, died after winds shifted and it became buried in blowing snow. It was, as Nelson describes, "a highly unusual, unexpected event," especially since the dog was clinically healthy and sled dogs are accustomed to hunkering down in blowing snow.
In 2014, the Iditarod experienced another year with zero dog deaths, something Nelson hopes to repeat this year.
"Obviously we are striving for another good year," Nelson said.
But perhaps the biggest breakthrough isn't much of a breakthrough but rather nurturing the human-canine relationships essential to the Iditarod.
"It's not that it's better knowledge . . . but better execution of the knowledge that we've had. And that's really a people thing," Davis said.
One of the most under-recognized advances, Davis said, is "the fact that veterinarians are getting better at examining the dogs and the mushing community is getting better at understanding and appreciating the fact that it is better to have the dogs looked at and dropped when small issues crop up."
This year, Nelson, the race's chief veterinarian, will head a team of 55 volunteer veterinarians, 45 of whom will be at checkpoints from Fairbanks to Nome. The other 10 veterinarians will watch over dropped dogs, among other tasks.
Improving human medicine and dogs of war
Unlocking the secrets behind the outstanding physical capabilities of Iditarod dogs has piqued the interest of researchers wondering whether those abilities could help humans combat illness -- or help canine soldiers perform better on the battlefield.
What if there was a way to help people stay slimmer and healthier? When human bodies stop using muscle as a storage location for glucose, they can develop obesity and diabetes, Davis said. It's here that unlocking more about how the dogs' bodies perform may hold promise for humans.
"It is known that exercise specifically and fitness in general can reverse this defect but it is not known how," he said. "When you combine those facts with the fact that the sled dogs appear to be very effective in managing their blood glucose despite their high-fat diet (a known risk factor for humans), you have the reason for investigating precisely what the dogs are doing with their glucose and how that changes with exercise and fitness."
Davis said his research team found that dogs appear to have a novel mechanism for boosting their ability to store glucose in muscle -- "one that is extremely efficient but had not yet been described in other species."
It takes a lot of exercise to stimulate the mechanism in dogs but it may not take as much in humans, leading to what Davis calls perhaps "the single most important tie-in to improving human athletics and human medicine."
"The next steps are in the human … realm," he said. "See if you can identify the mechanism in humans, then work on figuring out how to activate it without days and days of exercise."
Other research efforts have focused on how the dogs manage body heat. Sled dogs run in frigid subzero cold during the Iditarod but war dogs operate in places like Iraq that are exceedingly warm. Studying the dogs has given Davis and his fellow researchers new insights on "water requirements and dietary adjustments that can reduce water requirements, and better means of monitoring the dogs' body temperature so that they are operating at peak effort but not overheating," he said.
Lance Mackey à la fin de l'Iditarod 2010

L'un des chiens de l'attelage de Lance Mackey (dossard 30) est décédé entre les checkpoints de Tanana et Ruby. C'est le deuxième chien de cette 43 édition de l'Iditarod, une course de chiens de traîneau de  en Alaska, à décéder cette année, après que l'un des chiens de Lachlan Clarke (dossard 5), nommé Stuart, est mort renversé par une voiture lors du départ cérémoniel à Anchorage.

La cause de la mort est pour le moment inconnue ; le chien, Wyatt, âgé de trois ans, avait bien été examiné par des vétérinaires à Tanana et semblait alors aller bien contrairement à son musher, dont les mains avaient souffert du froid. Comme le règlement l'exige, Lance Mackey a amené le cadavre de Wyatt jusqu'au checkpoint suivant, où il sera autopsié pour déterminer la cause de la mort.

Wyatt est le premier chien à mourir alors qu'il courrait l'Iditarod depuis 2009. Outre la mort de Stuart cette année, un autre décès accidentel avait eu lieu en 2013, lorsque l'un des chiens de Paige Drobny, confié aux volontaires à un checkpoint car trop fatigué pour continuer la course, était mort enseveli sous la neige lors d'une tempête. L'une des causes de mortalité des chiens sur la piste était la propension aux ulcères d'estomac, difficilement détectables et très fréquents chez les chiens de traîneau ; les vomissements pouvaient amener les chiens à s'étouffer en courant. Depuis cette découverte, des anti-acides gastriques ont été ajoutés au traitement des chiens, diminuant considérablement les pertes canines dans les courses.

La première autopsie pratiquée n'a pas livré de résultats probants et d'autres examens seront effectués.