by Jay Leimbach ©

Even among the very best stud prospects, no more than 25% go on to enjoy successful stud careers. A good stud is evidently a genetic freak and the sire-of-sires is rarer still. Nasrullah, Turn-to, Ribot, Northern Dancer, Mr. Prospector, Damascus, In Reality, Roberto, Blushing Groom, and Seattle Slew are among the handful of noteworthy sires-of-sires over the past 50 years in North America.

On the other hand, curiously, the best broodmare-sires were often disappointing sires-of-sires, suggesting some sort of genetic gender connection. In fact, when a top sire then becomes a top broodmare sire, it usually foreshadows the demise of the male line. Sir Galahad III and Bull Lea were many-time champion broodmare-sires whose male lines quickly waned...likewise Princequillo, Buckpasser, Hoist The Flag, Secretariat, and Alydar.

Now we see that Mr.Prospector has topped the North American broodmare sire list the past four years. Does this foreshadow the future decline of his male line...?

Northern Dancer, on the other hand, became a good but not great broodmare sire, while leaving four sons who were very nearly his equal at stud: Nijinsky II, Danzig, Nureyev, and Sadler's Wells. Nijinsky II (147) topped Northern Dancer's all-time record of 146 stakes winners, and now we find Sadler's Wells (184), Danzig (163), and Nureyev (128) in the same stratosphere.

Conversely, Mr.Prospector left only one son who rivaled him at stud: Fappiano, who died young after leaving behind sons like Unbridled, Cryptoclearance, Roy, and Quiet American. If there is a genetic factor in such gender bias, it seems probable that the X and Y Chromosomes are involved. These are the chromosomes most directly connected to gender. A stallion (XY) has one of each. If he passes on his X, the offspring is female; if he passes on his Y, the offspring is male. The X-Chromosome, already linked to heart-size, thus becomes a candidate for creating good broodmare-sires, and sires from top female families should benefit most. The Y-Chromosome, which is passed on from father to son, appears to contain very little genetic material, but perhaps there is a key gene there with potent abilities that earmarks the best male lines.

Nasrullah was a foal of 1940, for example, but his male line is till thriving through the likes of Seattle Slew, A.P. Indy, Rahy, Mt. Livermore, and Cozzene. Curiously, Nasrullah was not a phenomenal broodmare sire, as is often the case with sires-of-sires. Again this suggests a genetic basis which is worth noting. Nasrullah's son Bold Ruler similarly was influential as a sire-of-sires but was not a great broodmare sire. The same could be said for Turn-to, Roberto, Damascus, In Reality, and even Northern Dancer. The only stallion to appear on the list of sires-of-sires and top broodmaresires is Mr.Prospector. Time will tell his destiny...

October 21, 2001. Copyright by Jay Leimbach 2001.