Select Sires has rather amusingly noted how much we love Denzel’s unusually big curved ‘leaf-shaped’ ears.
There’s an incredibly important reason.
While we recognised ‘those ears’ as being identical to those on Native Son, a full brother to Night Bird, his grand dam, there’s more to the story than a lovely memory of seeing the cattle muster through the big ears of a good horse.
According to the rules of genetics, Native Son inherited his ears from his dam’s sire Skymark, who was a grandson of the Melbourne Cup winner Hall Mark.
Hall Mark appeared to carry the large heart gene since he won the Melbourne Cup was still only a 3YO, which is unusual for a staying race where most winners are usually five- or six-year-olds.
Hall Mark was an extraordinary race horse who raced from 1200 m to 3200 m and won the 1933 AJC Champagne Stakes, the 1933 AJC Derby, the 1933 AJC Sires Produce, the 1933 Underwood Stakes, the 1933 VRC Derby and the 1933 VRC Melbourne Cup all in the one year – and all as a 3YO colt.
Back in 1983, when Native Son was a 10YO stallion, I took him out of my mustering string and travelled him across to Winton where he travelled beside R.M Williams Arab endurance mare for most of the journey.
RM had invited me to accompany him on the 241-km Winton to Longreach Endurance Ride to help promote the concept of building a Stockmen’s Hall of Fame in Longreach.
After Native Son had so effortlessly completed the first 32 km leg and vetted through, we decided to continue onto the next leg.
He once again came through with flying colours and – since R.M.’s other riding partner had suddenly been forced to withdraw – R.M. had nobody to ride on with, so I agreed to ride on to the next checkpoint.
R.M’s mare then vetted out – and Native Son once again vetted through.
The next morning, we left Maneroo Station and travelled the 56 km into Longreach at a fast pace, completing the journey in 2 hours and 11 minutes.
Once we crossed the finish line at Longreach the vets swarmed around us and subjected the horse to the most stringent testing.
Once again, he passed with flying colours. Two hours later – when we had gone downtown to have a hot shower – he crawled out of his rope yard and attempted to serve a nearby mare before he was caught.
A large heart is a much-prized thoroughbred characteristic that is much sought after and rarely seen – and it is almost always found on champion horses.
A large heart in thoroughbreds is highly prized because it gives a horse greater stamina and strength.
The large heart gene is also known as the X Factor, because the gene is carried in the X chromosome.
Therefore, a colt can only inherit an oversized heart through his dam, and a stallion can only pass his gene into his daughters.
The exact heart size seems to vary from horse to horse.
Multiple factors probably contribute to heart size, and the X-factor gene, being a mutation itself, probably works in conjunction : it super-sizes the heart based on the existing blueprint, so to speak.
The gene can be passed from father to son and from mother to daughter, but in that case the gene is recessive. It only generates in the opposite sex.
Therefore, a dam may pass the trait onto her daughters, who in turn would bear sons with the large heart gene. This is one theory to explain how ‘class’ may skip a generation.
There is one unique physical characteristic found among horses with an active large heart gene. That is large ears with distinctive curly ‘leaf shaped’ ear tips.
A horse can be any size physically and still inherit the large heart gene.
Look at the ears of Phar Lap, Frankel, Secretariat, Zenyetta and Winx and you will see the evidence right in front of you.
That’s why we are so delighted that Denzel has carries those same large, distinctive curly ‘leaf-shaped’ ears.
It is an extremely rare thoroughbred characteristic that Denzel will be able to pass on to his daughters, and they, in turn, will pass onto their sons, and those sons will pass onto their daughters.
Those large ears and large hearts will give his descendants greater stamina and strength, a characteristic that made horses like Phar Lap, Frankel, Zenyetta and Winx the greatest champions of modern times.
While Denzel is a camp drafter and not a racehorse, the fact that he carries such a rare large-heart gene is evidence of the depth of his thoroughbred blood. No other breed carries the X-factor gene for a large heart.
It is also the reason why Denzel shows so much stamina and strength in his camp draft runs.