Page 73 - March 2017

“at the end of the day, however,
what makes a good racehorse is what we can’t see.”
Heart ScanS
It’s become popular to have young horses evaluated at sales, not only with a vet check and scoping but also doing an ultrasound of the heart. “Checking hearts is part science and part art;
it takes a lot of experience. When people first started doing it, they thought it would be the Holy Grail and that all you had to do was find a horse with a big heart. We’ve all heard the story about Secretariat’s 22-pound heart, or the big heart of the Australian racehorse Phar Lap,” he says.
“The people who are really good at doing heart scans have done thousands of horses and have a pretty good idea about them. Racehorse hearts come in all sizes. Victory Gallop had a small, powerful heart and he could run a mile and a quarter and really put on the afterburners when his rider moved his hands on the far turn. That horse would work exceptionally fast in the morn- ing,” says Casner.
“Generally, horses that have small, powerful hearts are sprinters and they are typically preco- cious. Their best races may be at two or three years of age. When you start asking them to go longer distances, they may not be able to do that. But, you sometimes find a few that break that model,” he explains.
“Then there’s the AP Indy type of heart, which is a great big heart with thinner walls—more like a bellows. It takes a lot of training to strengthen that heart. Generally, it’s the middle-of-the road
kind of heart that does well. There are so many things that are involved in what makes an efficient heart besides the size. There’s stroke volume, and the ability to sustain its effort for a long period,” he says.
The horse’s heart, beating at full tilt during exertion, will beat about 230 times per minute. “To put that into perspective, just try to open and close your hand four times in a second and keep doing it. It’s difficult to sustain that action. Training can certainly have an effect on a horse’s endurance muscle-wise, including the heart,” says Casner.
tHe raceHorSe IS an amazIng anImal
“When we evaluate horses, we can ultrasound the heart, scope them (some have smaller throats and don’t take in as much air), etc. The horse is a tremendous athlete and has evolved from running away from predators in order to survive. The horse used speed over a fair distance of ground
to outrun the varmints that wanted to eat him.” Now, we’ve fine-tuned that ability with selective breeding to create very fast horses.
“It is amazing what some of these good horses can do, and the things they can overcome. You can have a horse like Distorted Humor that looks like a running Quarter Horse because he was a big, strong horse with a big hip and he was fast! He won going a mile and 1/16th, but he had the ability as a stallion to sire horses that can run 1
1/2 miles and win the Belmont or the Kentucky Derby (1 1/4 miles). He sired countless horses that could carry their speed that far. There was something in those genetics that came through for distance speed in spite of the way he looked,” says Casner.
“Northern Dancer was a small horse and looked like a 15-hand Quarter Horse, but he broke the mold. He looked like a horse that you’d love to make a heading horse out of for team roping or to use as a barrel horse. He was small and catty with a great hip, yet he could run 1 1/4 mile and he could sire horses that ran that distance. It’s hard to tell by looking at a horse what he can do. This is one of the most difficult things in the business—predict- ing how fast a horse will be and for how far. When we look at a horse, we cannot see how much speed he will have or how far he will run. We think we can see things that might help him do that, but we really don’t know,” he says.
“Speed is the toughest thing in the world
to see in a horse. You really don’t know until
you train them and try them. I’ve come to the realization that it doesn’t matter if it’s a Quarter Horse, Thoroughbred, a dressage horse, a 3-day eventer, a bull-dogging horse or a calf-roping horse—every one of them has a certain talent in a certain area. What you hope is that the horse you pick for a certain career has a talent for what you want him to do. If he doesn’t, he’ll need a change of career!”
It’s popular to have young horses evaluated at sales with a vet check, scoping, and an ultrasound of the heart. There are many things that make an efficient heart beside the size, such as stroke volume and the ability to sustain its effort for a long period. A horse’s heart during exertion will beat around 230 times per minute.
1973 Triple Crown winner Secretariat (above) had a heart that weighed 22 pounds, while 1998 Belmont Stakes winner Victory Gallop had a small, powerful heart.
SPEEDHORSE, March 2017 71
equine health