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6 August 2008


By Tom Reed
Horse International Vol 7 2008.

Throughout the world during the 20th century the thoroughbred (TB) stallion enjoyed a privileged status in sport horse breeding. In many breeding areas, especially in Europe, the special role for TB stallions was rooted in the need to lighten and to make more athletic traditional indigenous horses used in agriculture. So in Ireland, for example, TB stallions were bred to Irish Draught mares to produce useful hunters and many became very competitive showjumpers. Not just in Ireland but in all breeding areas throughout the world the TB stallion played a vital role in the development of the modern sport horse in all three Olympic disciplines. But will TB stallions continue to play a pivotal role in sport horse breeding in the 21st century? Or are the glory days over?

The best evidence that the glory days have passed is the Irish Horse Register. Here we have a studbook with over 100 approved TB sires (yes, over 100!) that has been increasingly uncompetitive over the two decades in producing international showjumpers. In 1998 37.9 percent of foals sired by approved stallions in Ireland were sired by TBs. (In 2006 the percentage had slipped to 27.10 percent). But there are no data to suggest that these half-bred foals born in 1998 have developed into exceptional showjumpers. In fact, the data show the opposite.

In the ranking of international showjumpers for the year ending 30 June 2008, there are 31 horses in the top 1,000 in the world with the breed code of ISH (Irish Sport Horse). None of the ISH horses in the world's top 580 showjumpers was sired by a TB; only two ISH horses in the world's top 735 were sired by a TB. Further, only 9 of the ISH horses in the world's top 1,000 showjumpers have a TB as the damsire, and only one of these is in the top 250 showjumpers in the world (Mo Chroi, ranked 249, is by Cruising and out of a mare sired by Mr. Lord xx).

This "natural experiment" in Ireland of the widespread use of TB stallions in showjumping breeding, combined with the poor breeding results in the few other countries that continue to use a lot of TB stallions and mares in sport horse breeding (for example USA, Australia, and New Zealand), and the much better results from studbooks that approve just a handful of TB stallions and use them very selectively (for example, KWPN, Holsteiner, Hanoverian, Belgium Warmblood, Danish Warmblood, etc.), suggest to me that for showjumping breeding the old formula has not worked for the last two decades and will not work in the future.

In fact, if not for the contributions of the Holsteiner stallion Cavalier Royale the Irish studbook would no longer be in the top 10 studbooks for producing international showjumpers (it is currently ranked 10th) and would not be the top eventing studbook. But the Irish studbook still clings to the old formula although it no longer works, and even has begun approving TB stallions based exclusively on their track performance – sight unseen, with no assessment of their riding horse qualities. Apparently some people still think the most important criterion – in fact, the only criterion – required for a sport horse sire is speed on a race track!

Let's step back from the data and explore why TB stallions have been used in the past and whether the reasons for using them still hold today. I like to think of TBs as potentially making contributions along three dimensions: genotype, phenotype, and athletic expression.

The first dimension, "genotype", is the genetic structure of the horse determined by the genes it inherited from both parents. In sport horse breeding TB stallions have played a useful role in the past by contributing genes that offered the potential to produce a lighter and more athletic horse; in other words, a horse better suited for a saddle rather than a plough! In addition TBs have been useful by serving as an out-cross to reduce the degree of inbreeding and to introduce greater genetic diversity in a population of horses, resulting in "hybrid vigor".

But today almost all TB stallions and broodmares do not contribute genes that will produce a better athlete for today's Olympic discipline (with the partial exception of eventing, which is seeing a shift away from TBs in sport toward horses whose pedigrees look more like modern day showjumping pedigrees with a bit more TB blood up close). Except for those very rare gifts from the fertility gods – such as Lauries Crusader xx in dressage breeding and Heraldik xx in showjumping and eventing breeding – most of the TB sires used in the last decade have tended to damage if not destroy the jump and canter. To me this is not surprising because TBs are not bred to jump or move in the way that sport horse breeders and riders want their horses to jump and move. And even the National Hunt TBs, which do race and jump, do not make the shape over a fence (the bascule) that is required for upper level showjumping and, to a lesser extent, eventing. And they are bred to gallop and not to walk, trot and canter.

Further, with the widespread use of shipped chilled semen and frozen semen the genetic diversity that TBs can contribute is not as important today as in years past. In my own breeding program I have genes from Germany, Netherlands, France, Denmark, Belgium, Ireland, and Russia. I have no need to use a TB to introduce greater genetic diversity into my herd and I doubt that many other breeders do either.

The second dimension, "phenotype", is the observable physical manifestation of the expressed genes in the horse. It is the flesh and bones that we can see and touch; it is the physical expression of the genes inherited by the horse from his sire and dam. TB stallions have been used over the years to change the phenotype of the sport horse: to make a more athletic horse with a lighter, more rectangular skeleton with longer legs.

But today there is less of a need for the TB stallion in sport horse breeding with respect to phenotype. The first reason is that many breeders belonging to some of the major studbooks (especially the KWPN) have been putting a greater emphasis during the last few decades on producing a more elegant and rectangular sport horse. They are producing a "type" of horse that looks like a half-bred "blood horse" but only has about 40 – 60% TB genes, and these TB genes are often found several generations back in the pedigree. By placing a strong emphasis not only on specialized athletic ability and conformation but also on "type" the KWPN and some other studbooks are producing modern and elegant horses without having to rely on TB stallions that can damage the jumping ability and movement in their progeny. These sport horses look like classic long-lined TBs and half-breds but move and jump like what they are: modern warmbloods.

The second reason is that there has been a strong divergence in the last few decades between the phenotype of the successful racehorse and the phenotype of the successful sport horse. For example racehorses are bred to run fast over short or long distances; they are not bred to carry themselves in a way that much of their weight can be transferred to the hind legs. The structure of the body of the racehorse is not ideal for the job that is done by sport horses competing in the Olympic disciplines. Why would we expect them to reliably produce progeny that have the body structure required for our sports?

Lastly, by "athletic expression" I mean how sensitive and reactive is the horse? Does he have a quick or slow hock? Does he move with energy or lethargy? At the end of a three-day show is his petrol tank empty or does he still have energy and power to offer the rider? Does he have quick reflexes to help both himself and his rider get out of trouble or does everything seem to move in slow motion?

TB stallions were very important several generations ago to improve the athletic expression of sport horses, whether they were Irish Draughts, other indigenous breeds, or old-fashioned warmbloods. But in recent years breeders have focused a great deal of attention on improving the athletic abilities of sport horses through careful selection of breeding stock – both sires and dams – and culling. Particularly in those breeding populations mentioned above that have developed very focused and specialized breeding programs a cost - benefit analysis of using TB stallions is bound to result in the verdict of using TBs rarely and very selectively.

The role of TBs is diminishing and will decline even further in future years because the potential contribution they can make along the three dimensions of genotype, phenotype and athletic expression is quickly eroding. In my own breeding program, which is aimed at breeding international horses for all three Olympic disciplines, I have employed TB blood but very selectively. For example, I own a mare sired by Mytens xx, who was one of the better TB sires in Dutch breeding (her dam is the international jumping mare Dante by Voltaire). I own another mare whose breeding is Cruising x Ozymandias xx x Nordlyss xx; Ozymandias and Nordlys are long deceased but they both produced many excellent showjumpers in Ireland (and Nordlys xx is the sire of Cruising's dam, Mullacrew, who herself was an excellent showjumper). I own a mare that is a daughter of Herka xx, the full-sister of the very important sire Heraldik xx; my mare has two brothers that are approved stallions in Germany. My stallions are infused with top TB blood from Ladykiller xx, Lucky Boy xx, and Erdball xx. I bred mares to Heraldik xx and used young stallions with Lauries Crusader xx and Heraldik xx as the sire or dam-sire. And in my liquid nitrogen tank, waiting to be used, is semen from the very interesting young Holsteiner stallion Mighty Magic (by Mytens xx and out of a mare sired by Heraldik xx and descending from a classic Holsteiner motherline). But in the land of over 100 approved TB sires there is not a single one that I have used in my breeding program.

In future years TBs will still be used in sport horse breeding but they will not enjoy a privileged status. Instead, they will be assessed as sires and broodmares in the same way that any sire or broodmare is assessed: athleticism, jumping technique, movement, rideability, conformation, trainability. The TB stallion will always be considered but his special role in sport horse breeding no longer exists.