THE COMMERCE OF GENETICS

There’s an underlying and unavoidable truth to the Thoroughbred Industry. We have tied a considerable amount of economic output, or commerce, to a sport.

We can duck and dive around to justify how and why this came to be, but well before we were talking about yearling averages, pinhooking profits and trifecta payouts, horse racing was quite simply a matter of one person wanting to prove that his horse was faster than another’s. It was a sport, one which eventually coalesced around a single breed, the thoroughbred, a majestic breed that for over three hundred years has been cultivated to run fast over a variety of distances.

In his TDN column Taking Stock, Sid Fernando outlined what he thinks are some of the likely commercial ramifications of the decision of the Jockey Club to limit the number of mares that a stallion can be bred to in North America. The flip side to the commercial coin, is the consideration of the breed on which the commerce has been built. One does not exist without the other.

The thoroughbred is built on assortative matings. That is, in each country that breeds and races thoroughbreds the breed has developed in accord with the individual traditions and socio-economic conditions prevailing in those countries. As a result horses with similar phenotypes mate with one another more frequently than would be expected under a random mating pattern in nature. We buy mares and select stallions because we believe that we are going to breed a horse that suits the racing environment to which it is born. Because performance is a manifestation of genetics, we tend to buy, import or collect - often unintentionally and even under the guise of an “outcross” (on paper at least) - individuals of a similar background.

Genetics in populations can adapt over time, especially when the weighting of the races within the Pattern or Graded stakes system are changed and new races implemented. This change might initially be an apparently marginal deviation from the median, but persisted with over time, leads to specialist development. It’s why over time the Australian turf sprinter has become good as it gets, the Japanese turf stayer has emerged as a world force, and the North American classic dirt horse is somewhat on a island of its own making.

Those developments are indicative of the broader principal that underlies every day commercial decisions that guide the development of the breed: Along that line of thinking is the underlying commercial decision that is being made with the breed every day – what survives in our gene pool is what we value. Think about a horse like Smarty Jones. As talented as he was, and as good an opportunity as he initially received at stud, retiring in 2005 to a full book of 113 mares at $100,000 a cover. Just fourteen years later he was down to 33 bred at a fraction of his starting fee. There is just one son of Smarty Jones to be found at stud in North America, and not one stallion in the country out of a Smarty Jones mare. What is more, out of the 4,648 yearlings catalogued at the Keeneland September Yearling sales in 2019, only 7 of these were out of Smarty Jones mares. Think of the 100’s of daughters he has had at stud, some out of great racemares and great producers, and our largest commercial sale only had 7 yearlings out of mares sired by him.

The average generational interval, that is the difference in age between each generation, is 10.6 years in North America, so in less than two generations of time, we have almost totally discarded the genetics of a horse whose athletic talent completely dazzled us at the greatest of heights. Why? Because he failed to provide us with the talent for the next generation, and more specifically, did not produce a sire-son early in his career. R.A Fisher, he who gave us the p value in statistics, described the genesis of the “sexy son hypothesis” which states that a female's ideal mate choice among potential mates is one whose genes will produce male offspring with the best chance of reproductive success. The thoroughbred industry has a derivative of this – we breed to proven stallions, not because of their ability to produce superior runners, but their ability to produce successful sire-sons. In turn we breed to these sons, even when unproven as progenitors, on the basis that they too may be like their sire and produce successful sons.

The obverse to Smarty Jones is a stallion like Pulpit. He not only proved a proficient sire, consistently capable of producing high quality offspring, but he passed the most important test early in his career – providing a sire son. With successful sire Sky Mesa being his first son at stud and Champion sire Tapit his fourth, we held our nose to the abject failure of other sons of Pulpit, and indeed gave them an inordinate opportunity to succeed because of their qualification of being a son of Pulpit. Frequently, how long stallions stay in the game at the highest level is determined by the perceived likelihood of them siring a successful stallion son.

I hate to use a horse like Smarty Jones, and apologize to his connections for doing so as he was truly a fine racehorse, but he is a modern example of how quickly we discard genetics under commercial pressures of our breed. The commercial reference population, that is the active males and females that provide the next generation of horses, is two generational intervals, or about 20 years, so the bulk of our current commercial reference population is born between 1996 and 2016 and while Smarty Jones retired to stud right in the middle of this population in 2005, its likely that within 3-5 years his genetics will be completely lost as we select away from him to others. He is not alone in being lost to the breed each year.

If you consider just these two aspects – selecting genetics to suit our racing environment, and selecting genetics based on the ability to provide successful sire sons, and you begin to see how the gene pool in various countries is quite narrow. That’s just the fuse, however. The powder keg is the economic engines that we have built around stallions – think of sales nomination teams, high powered syndicates and the like – and combine that with improved veterinary practice, and we get the following:

In 2014 Australia had 19,386 mares covered by 668 stallions while in 2018 they had 20,303 covered by 578. The math is simple there in that there was an average of 29 mares per stallion covered in 2014, and then just four years later it increased to 35 mares per stallion. That is some jump in a short period of time.

Australia appears to many to be in a unique spot in the world, however, in that it can have both its domestic stallions, possibly two or three generations separated from a major imported sire, and also import or shuttle stallions from North America, Europe and Japan. No other country, outside of New Zealand, has the possibility of such diversity that Australia sees each breeding season. Despite that, it does invariably get back to a point that I was making earlier – because of commercial considerations and the way we have set up the Pattern/Graded system in each country, we tend to select for genetics that has worked to produce the phenotype that we want. To wit, taking those 578 stallions that stood in Australia 2018 (some very uncommercial ones amongst them), in theory if every ancestor in each of those stallions was unique, you could have 9,248 unique individuals represented (587x16). In reality, there are only 1,947 unique names with the rest being duplicated across the stallion population. At their 8th generation they could in theory have 295,936 unique individuals (578x512) but they have only 3,692. The lack of genetic diversity, or the commonality of pedigree between all the stallions in Australia has a compounding effect on its broodmare population over time (Note: Australia went from 578 stallions in 2018 to just 455 in 2019).

The genetic difference, at least on paper, between the stallions at stud in Australia is very small. While it might look like they are different, within 8 generations, the same names are floating around in the background repeated many times over. Furthermore, as you make the genetics of the stallions homogenous, by selecting heavily on them (that is the ‘bar’ to becoming a commercial stallion in terms of racetrack performances is raised to a higher level as less stallions cover more mares), the difference between them narrows. This conversely turns most of the difference in the outcomes of yearlings on the racetrack back to the mares, as they are the ones with the higher variation of the two parents. It’s why, somewhat perversely, we now see a more consistent correlation between the racing quality of the dams of yearlings as runners, and the performance of their offspring. The stallions are providing less variability to the outcome and the adage that the stallion is only as good as the mares he is bred to is becoming more true.

Over time, however, there is a genetic price to pay for the predominance of a limited number of sires and sire lines. As individual stallions serve a higher proportion of mares, and there sons also become a focal, we simultaneously discard the genetics/daughters of less successful sires more quickly than before. Consequently the gene pool starts to narrow at a molecular level, not just on paper. The breed began with an admix of Arabian, Turkoman, Irish Cob and English ponies, so close inbreeding from many of the stallions and mares now considered our founders had the effect of increasing their fitness, that is making them faster, where we are now starting to get to the point where this same inbreeding has the potential to become a deleterious event.

In 2011 Dr Binns and colleagues conducted a study of changes in inbreeding at a molecular level over the past 45 years by genotyping 467 Thoroughbred horses (born between 1961 and 2006). Their results indicated that inbreeding in Thoroughbreds has increased over the past 40 years and that the majority of the increase in genetic inbreeding is post‐1996 and coincides with the commercialization of stallions covering larger numbers of mares. More recently Dr. McGivney and colleagues studied a more comprehensive 10,118 horses at a genomic level, and found that over a 50 year period there has been a highly significant decline in global genetic diversity. The science is indisputable and clear – thoroughbreds are becoming more inbred and the rate of inbreeding is accelerating.

Noteworthy in the latter paper, however, is that that the authors note that there is some level of regional variation that may be exploited to improve global genetic diversity. That is, for some period of time, stallion masters in North America, for example, could scramble around, trying to find the next Noholme II, Forli, Hawaii, Wolf Power or Strawberry Road to import, and through a process of trial and error, and with considerable wastage as a by-product, will succeed in maintaining some genetic diversity.

It is possible that without the aid of a molecular/DNA understanding of genetic diversity, we can continue this trial and error process for some time. Since, however we have a closed stud book, and opening it up to infusions from other breeds is simply not practical, thoroughbred populations are inevitably going to run into the problems associated with inbreeding depression. It is an inevitability set up by the commerce we have grafted to the sport.

It’s certainly hard to establish with any precision - and without genetically sampling a significant number of horses in every country, to understand the true depth of genetic diversity that is available to us – as to when the time comes that an inbreeding depression becomes a global issue. It’s equally as hard to know how, when the time comes, it will manifest itself. It could be a fertility issue (most likely) or a soundness issue. But when it does come, and it will, because we have a closed stud book it won’t be possible to breed ourselves out of the corner, and we won’t know its arrived until it’s too late to do anything about it.

So, while it’s possible that it doesn’t end up quite as binary as this, what is more palatable? As in-artful as the Jockey Clubs limitations might seem to some, it is a positive move towards maintaining genetic diversity. Is it not better for us to make some smaller considerations now and begin to create a framework that will hopefully maintain genetic diversity of the breed, or should we all just ride the “freedom of commerce” horse along until we have the breed collapsing on itself with no way out? The horse, as a breed has for many of us sustained our lives both personally and professionally. It probably behooves us to look after the breed as a primary concern, if we still want a sport to attach commerce to.

P.S. For full disclosure, I also part own and manage TrueNicks, a company that is indirectly partly owned by The Jockey Club through its ownership of Blood Horse Publications. TrueNicks is a commerical entity with commercial outcomes based on stallions. I haven't discussed with any of the "powers that be" at TJC as to their position and why they have taken it, but I am in support of what they have disclosed, primarily as I believe that the moment we lose sight of our care of the breed, and prioritize profit or commerce over breed welfare, we aren't viewing the breed for its long term sustainability.