Horses With a Big Heart

Because Quarter Horses long have been crossed with Thoroughbreds, the great heart line found its way into the sprinters years before AQHA was established. the “big hart” is passed through sires such as:
A Classic Dash
Aforethought (TB)
Alamitos Bar
Azure Te (TB)
Beduino (TB)
Bugs Alive In 75
Calyx
Chicaro Bill
Chicks Beduino
Dash For Cash
Dash Thru Traffic
David Cox
Depth Charge (TB)
Diamond Charge
Dividend
Double Devil
Easy Jet
First Down Dash
Go Man Go
Hempen (TB)
Holland Ease
Jackstraw (TB)
Jet Smooth
Jonny Apollo
Lake Erie (TB)
Leo
Little Request (TB)
Merridoc
Mito Paint (TB)
Moolah Bux (TB)
Moon Deck
Pass ’Em Up (TB)
Piggin String (TB)
Raise Your Glass (TB)
Rare Bar
Rare Form
Rocket Wrangler
Ronas Ryon
Royal Quick Dash
Special Effort
Spotted Bull (TB)
Streakin Six
Takin On The Cash
Texas Dancer (TB)
The Signature
Three Bargains
Three Bars (TB)
Three Chicks
Three Oh’s
Tiny Charger
Top Deck (TB)

X Factor – Term that geneticists use to describe the female X chromosome, which is attributed with creating the large hearts found in outstanding racehorses.

Heart score – Term coined by Australian researcher Dr. James Steel to communicate his findings of the heart size on the electrocardiogram, which was gained by a correlation of heart weight, stroke volume, cardiac output and aerobic power.

Double copy – Describes the ideal broodmare, which has the large heart on both X chromosomes. If the mare is bred to a large-hearted sire, she always will produce large-hearted foals. Her daughters also will be double copy mares. Double copy mares frequently produce all winners.

Though his blood flows through other notable racehorses -X Y Chromosomes -including (especially) 2004 Kentucky Derby and Preakness winner Smarty Jones, Secretariat turned out to be a noted broodmare sire.

so , if you have a good stallion , his power will not be seen from his offspring foals , but rather from ones of its broodmares that he was assigned to?

There has been some criticism of Secretariat as a stallion, due in part to his perceived inability to produce offspring of his same caliber. His expensive syndication deal, perhaps, raised unrealistic expectations. Ultimately, he sired as many as 600 foals during his retirement.