Full Siblings
by Jane Henning www.pedigree-dynamics.com.au

Why is it that full brothers and sisters to top performers don’t always live up to expectations?
From (this) pedigree analyst’s point of view, there are two major reasons for the same sire and dam combination coming up with radically different racing talent in their offspring; parent compatibility and parent prepotency. Other reasons why repeat matings may fail are: advancing age of one or both parents, affecting sperm quality or uterine efficiency; nutrition and of course, the usual injury and management problems
right up to race day. While not very common, some stallions and mares produce better racehorses of one sex. Therefore full relations of the opposite sex may be less likely to perform.
Parent Compatibility
The pedigrees of high performing racehorses are under a lot of scrutiny as breeders and analysts try to fathom what special pattern or family buildup is responsible for the exceptional ability. Like gambling, genetics and inheritance are all about ‘odds’.
From my perspective, the mating compatibility of some high level performers is relatively low. There are minimal elite family buildups or other dynamic patterns created in the mating of their parents. So why are these horses so talented? Like pulling the arm of a pokie machine or taking balls out of a lotto machine, there is always a chance that you can hit the jackpot. So, despite the reduced odds of doing so, one instance of the mating of these two parents has managed to eke out all the best attributes of both parents.
In theory, repeating this mating several times is not likely to be able to reproduce the ability level of this progeny.
Highly compatible matings, where the combination of these parents creates a dynamic and genetically strong pedigree, are much more likely to produce more than one top performer, especially if the parents are both in general, from successful families.
Parent Prepotency
The term ‘prepotency’ refers to the ability of a parent to pass on his or her positive attributes to their progeny. Sometimes however, there are top performers from parents whose pedigrees and other breeding performances have been poor.
Getting another stakes winning full relation from this mating tends to be difficult. A prime example would be Veandercross, the product of a highly dynamic mating that produced inbreeding to Nijinsky II through a son and a daughter on his third remove, and the meeting of Sir Gaylord and his half sister on the third remove.
His sire Crossways only produced two other stakes winners in his career. Veandercross’s dam, the unraced Lavender, had a total of nine foals to race for three winners. Her first foal was Veandercross’s year younger full brother, Regal Crossing, whose race record features one country placing in New Zealand. After Veandercross’s deeds in 1993, culminating in being crowned both Australian and New Zealand Horse of
the Year, Lavender was put to more commercial stallions, such as Centaine and O’Reilly without any high achievement. Neither of Veandercross’s parents proved to be prepotent.
In comparison, repeat matings of stakes winners with one or more prepotent parent (which may not be evident until later on) have a much higher strike rate in reproducing their success. For example, the Danehill – Shantha’s Choice matings have produced four foals for two stakes winners (Redoute’s Choice and Platinum Scissors) and two stakes placegetters (Monsoon Wedding and Superior Sateen). Not only do we know that Danehill is prepotent, but Shantha’s Choice is from the highly prepotent BEST IN SHOW branch of the TORPENHOW family.
In summary, put two prepotent parents together, ensure that the foal gets as good as or better nutrition, training and management and you will get as close as you will ever get to guaranteeing yourself a successful repetition of a stakes winning mating, especially if it is the same sex!