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Are racehorses being bred to destruction?

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Matt Walker Matt Walker | 15:05 UK time, Friday, 18 November 2011


Bred to race or be sold? (copyright: Slooby)

“Just hours before the Kentucky Derby, trainer Larry Jones got up early with his filly Eight Belles and took her to the track for a ride before the big race.

This was supposed to be a day of tempting history for Jones and Eight Belles.

They were taking on 19 colts and trying to make Eight Belles the fourth filly, and the first since Winning Colors in 1988, to win the "Run for the Roses."

This was to be a day of celebration for owner Rick Porter and his entourage no matter where she finished. She was the first filly to enter the Derby since 1999.

Now there will be a necropsy and then cremation.”

The excerpt above is taken verbatim from a USA Today news report filed hours after the racehorse Eight Belles was euthanized on the track.

She was put to sleep after fracturing both her forelegs while pulling up after the race, in which she finished a glorious second, running, in the words of USA Today, “the race of her 3-year-old life”. 

The tragedy occurred just two years after the Derby winning horse Barbaro fractured his leg in the second round of the US Triple Crown, a race called the Preakness.

These and other inexplicable injuries to racehorses (in July the racer Rewilding snapped his leg challenging in the King George VI and Queen Elizabeth Stakes at Ascot in England, a tragedy I witnessed from the stands) inevitably leads to questions about the quality of the ground on which the horses run, the age at which they run, whether fillies should race colts, and most pertinent of all from a science or natural history viewpoint, has breeding caused a weakening of the racehorse talent pool?

Eclipse racehorse

Eclipse was a famous, unbeaten founding Thoroughbred

New scientific research just published helps inform this last point; for it suggests that Thoroughbred racehorses around the world are becoming more inbred.

Not only have Thoroughbreds become more inbred over the past 40 years, the research shows, but the rate of inbreeding has accelerated over the past 15 years.

Thoroughbred horses, by definition, suffer relatively high levels of inbreeding. Just 21 horses mated at the turn of the 18th Century founded most of the racehorses running today, accounting for 80% of the genetic makeup of the current population. Other genetic analyses have shown that Thoroughbreds are the most inbred of horse breeds examined.

“However, to put these results into a broader context, the Thoroughbred is not as inbred as most pedigree dog breeds,” Matthew Binns, an expert in horse genetics, tells me.

But questions about the quality of the breed led Dr Binns, previously Professor of Genetics at The Royal Veterinary College in London, UK, and a founder of the Horse Genome Project, to investigate further.

Dr Binns has spent a significant portion of his career investigating the genetic basis of racehorse performance, and has a massive set of genetic data taken from horses sampled from the 1960s onwards.

“I realised I could answer the question about whether the Thoroughbred was becoming more inbred,” he told me.

Dr Binns and his colleagues, including Dr Jackie Cardwell from the Royal Veterinary College in London, UK who did the statistics, Drs Bailey and Lear from the Gluck Equine Research Centre in Lexington Kentucky, US and Drs Lambert and Boehler, colleagues at Equine Analysis in Lexington, Kentucky, US where Dr Binns now works, analysed the genetic profiles of 467 racehorses born between 1961 and 2006.

The racehorse Eight Belles

Eight Belles's career and life ended on the track

They analysed 50,000 separate markers, known as SNPs, on the genome of each horse, and then compared them to each other.

“DNA markers measure what was actually inherited rather than assuming an average as would be obtained by pedigree. For example, two full brothers on average share 50% of their DNA, but the real figure could theoretically range from 0-100%, depending on whether they inherited the same or the different chromosome from each parent.”

The study showed that there had been a small but significant (i.e. real) increase in inbreeding over the past 40 years, and that most of the increase was from the mid 1990s to present.

“Which is the time period during which many things have changed in the breeding of Thoroughbred horses,” says Dr Binns. “In the 1960s it was usual for each stallion to cover 40-50 mares per season, in the mid-1990s this number jumped to 150+.”

Nowadays, high quality stallions are also “shuttled” around the world to cover mares, for example, being sent to the southern hemisphere to breed with mares during the quiet season for breeding in the northern hemisphere.

This in part is to meet the modern demand for producing yearlings that sell for high prices at auction rather than the previous breeding goal of producing superior racehorses.

Overall that means fewer stallions are siring a greater proportion of offspring.

The current trend toward greater inbreeding is “worrisome”, say the scientists in the journal Animal Genetics, which has published their research.

Dr Binns says he doesn’t believe the inbreeding is, at the moment, greatly contributing to the number of fractures sustained by racehorses, and there is no evidence it directly led to the fractures of Eight Belles, Barbaro or Rewilding.

But he suspects it is contributing to the failure rate of pregnancy among breeding Thoroughbreds. So called “reproductive depression” is one of the first signs of inbreeding problems seen in populations of animals.

Scientists working with rare and endangered species face similar issues. In zoos and captive breeding programmes, researchers try to maximise “outbreeding” of their rare animals. That is to reduce the inevitable loss of genetic variation that occurs within a population due to a phenomenon called “genetic drift”.

They even set themselves a benchmark of maintaining 90% variation over 100 years within a population of animals.

As yet it isn’t possible to say whether Thoroughbreds are being bred to destruction.

It isn’t possible to link injuries to horses to inbreeding, or to conclusively say that inbreeding is damaging the fertility or fecundity of these horses.

But the trend isn’t good.

And no-one wants to be watching the Derby, Kentucky Derby or Prix de l'Arc de Triomphe in 2018 and to see another horse fall, broken under its own weight and heritage. 

To avoid such problems in Thoroughbreds, and to maintain the genetic health of these most athletic of animals, Dr Binns suggests that the Thoroughbred industry should periodically, every 5-10 years, re-check to see what the levels of inbreeding are.

That way, he says, it can “make sure that dangerous levels of genetic variation are not lost from this fantastic breed.”


  • Comment number 1.

    Is this story serious??? "there is no evidence it directly led to the fractures of Eight Belles, Barbaro or Rewilding"

  • Comment number 2.

    Couldn't agree more with the above comment. This article tries to suggest Eight Belles, Barbaro and Rewilding were injured as a result - a very very serious claim without evidence.

  • Comment number 3.

    There has definitely been excessive inbreeding to the prepotent Canadian stallion Northern Dancer since 1965.

  • Comment number 4.

    There are really two separate articles here:
    1) The unexpected deaths of several racehorses - possible reasons not explored here

    2) Increasing inbreeding of racehorse - explored here reasonably well. Difficult to see why humans have chosen to interfere so comprehensively in the breeding of pedigree dogs, racehorses etc. Shame on the gene manipulators here.

  • Comment number 5.

    Humans breeding anything usually ends in disaster. Captive bred mouse and rats live about half as long as one taken from the wild. The health and lifespan of a lot of pedigree dogs (e.g. german shepherds) are also appalling. Humans incorrectly think they can use simplistic logic to decide better than an animal's instinct developed from hundreds of millions of years of evolution.

  • Comment number 6.

    The thoroughbred racehorse has been improved to run faster and faster and that takes things closer to the edge of the physiology. Legs are a vulnerable part of the structure at any level not just top races. It is meaningless to pick 3 events out of thousands of thoroughbreds in training and thousands of races occurring. It has little to do with inbreeding which is a separate issue. Quite frankly it is a disappointing article. What is just as pertinent to the thoroughbred race horse is the oversupply of thoroughbreds which has nothing to do with the question of inbreeding.

  • Comment number 7.

    Why are some being so defensive and dismissive of the article? If there is a statistical correlation between inbreeding and fractures it should be investigated. There may be no causal link ie inbreeding is causing no problems in the thouroughbred population and the fractures are due to other factors. But equally there could be a causal link ie inbreeding does lead to weaker legs. Surely if the welfare of the horses is paramount a possible link should be investigated. Those who have already dismissed the possibility of link seem to be putting money ahead of welfare. They can't be horse lovers.

  • Comment number 8.

    I used to breed racehorses, so I speak from experience.

    The trouble is that just a few people dominate racing and their horses have been bred, by putting the so-called best to the best. There is too much North American blood in thoroughbreds. There they can race under medication, which is not good, as we've seen in some human sports. So often, you're breeding two basically unsound but very successful racehorses together.

    The trouble is the strong and sound lines, which for instance we see increasingly in National Hunt racing, don't get chosen by flat breeders, as if you haven't got the right blood as perceived by so-called experts, you won't sell your horse at the Sales.

    Some owner/breeders aren't so stupid and make sure they breed properly. Look at the pedigree of some really good European horses and they certainly don't follow the drug-corrupted American lines.

  • Comment number 9.

    A horse is not fully mature until it is six years old.

  • Comment number 10.

    7. Boilerbill

    'Why are some being so defensive and dismissive of the article? If there is a statistical correlation between inbreeding and fractures it should be investigated'

    I am quite open to statistics, I use them everyday. No statistics are presented. The probability is if they were given for fatal fractures in races they would look ridiculous.

    Read JM at 8 and further note that the trend has been to increase intake from the flat into National Hunt racing

    Note LfS at 9

    Further - no amount of breeding will stop fractures and it is ingenious to try and imply it will. Just like no amount of breeding in humans will stop stress fractures

  • Comment number 11.

    I have always maintained that it cannot be healthy for the Thoroughbred Horse to have so much Northern Dancer blood in their veins.
    I blame Coolmoore for this, together with the Irish Goverment for encouraging the mass production of horses, above and beyond their natural mating conditions.
    A top stallion these days covers 3 mares on average every day for 3 months, sometimes even sirinf a crop of 200 plus foals. The vast majority of which are absolute rubbish!
    I know it sounds old fashioned, but bring back the days of smaller books, syndicating of stallions and proper herd management. Thwn, and only then, will the Thoroughbred make his giant strides forward and evolve into a much better, more graceful animal than they already are!

  • Comment number 12.

    the whole industry stinks of greed and cruelty and this is the outcome deformed and fragile animals being pushed to their limits and beyond. we've tried to stop dogs being overbred how about horses??

  • Comment number 13.

    As a livery yard owner my job is to look after other people's horses. It is my experience that due to overbreeding, never mind inbreeding, ex racehorses often end up in the hands of well meaning folk who do not know enough to either look after them properly or ride them effectively. The same happens to Shetland ponies in Scotland but at least the Shetlands are better able to stick up for themselves. Thoroughbreds certainly have weaknesses that make them a lot less hardy and more prone to injury than other breeds.

  • Comment number 14.

    12 BfP

    Its always good to see a well thought out rational argument presented.

    Just one question. Have you ever owned a horse

  • Comment number 15.

    Riding horses arn't broken in until they are 4 years old. If you continue to race 2/3 year olds, you are going to come across serious injury like the one mentioned because their bones/ligaments are simply not strong enough to undertake that amount of pressure. Until people stop making big money out of the pain and suffering of these beautiful animals, nothing will ever change. The only time the industry shows any concern for the animals themselves is when they have lost a big 'money maker'. The thousands of other thoroughbreds who never make the mark are 'disposed of' as quickly as possible. If you continue to breed, there will continue to be a surplus of unwanted thoroughbred.

  • Comment number 16.

    This is ridiculous. There are so many people out there who disagree with horse racing and this is just another thing for them to complain about. It's a stupid assumption that injuries to Eight Belles, Barbaro or Rewilding was because of 'breeding to destruction'. More investigation should be carried out before publicising an article like this.

  • Comment number 17.

    This has been known about for years, I remember reading a study on the inbreeding of race horses and its effect on their health, fitness and fecundity back in the very early 90's.

    It's not at the level of pegdigree dogs yet (i.e. brains too big for their skulls etc.), but it is heading that way.

    Anyone with a basic understand of genetics realises this, however it's money (not an understand of genetics) that is the driving factor behind most humanised breeding programs.

  • Comment number 18.

    Horses are raced too young and too hard.
    Any time humans use animals to make money, they cause harm to the animals, whether by inbreeding or not. Flat race horses sometimes bleed from the lungs, they are pushed so hard.
    The first step would be to ban the use of the whip, and rely on the horses' natural speed and the jockey's skill rather than cruelty to get the race won. Then the horse wouldn't push itself past its limit.
    They should also raise the age at which horses can race - but they don't want to spend the money on keeping it for all the years it would take for the horse to mature.
    Racing people are selfish exploiters who dump vast numbers of horses before they even reach the track, and mostly abandon them when their career is over.

  • Comment number 19.

    pip_1 Perhaps you should accept that the purpose of the article is to raise a concern and get more investigation into the issue.

    Arthur Daley All I said was that it should be investigated. Unlike you I'm not pre-judging the outcome. I would be concerned if the stats were limited to fatal injuries during races. Perhaps the worst cases hit problems as foals or in early training. I don't know and I doubt you know either. Perhaps the incidence is no more than in the horse population in general. Do you know? If research is being carried out at the moment nobody knows for certain. And even then is it down to genetic factors or poor training methods or incorrect diet? In the interests of horses' welfare isn't it worth finding out? If you use stats a lot - you should know they usually raise more questions than they answer.

  • Comment number 20.

    Proportionally thoroughbreds have a smaller hoof size proportionally to their weight than any other breed of horse. Evidently an animal of nearly half a tonne landing on two single bone structures, with an exaggerated natural weight has its problems. Regardless of past breeding, more has to be done for future racehorses to safeguard their soundness.

  • Comment number 21.

    Just imagine the outrage if we did the same with Olympic athletes.....

  • Comment number 22.

    As a horse owner I have seen more thoroughbreds with bad legs than any other breed. By the age of two they are musclebound running machines and are galloped on many different surfaces. On average a horse does not stop growing until about the age of 4 or 5, so these baby's legs still have growth plates on them instead of solid bone. The two years old's are sold on or put down if they don't make the grade, the lucky ones who go on to new homes and re-training often suffer with health issues in later life such as arthiritis and splints from the pounding as babies. I am never surpirsed when a horse breaks down on the racecourse.

  • Comment number 23.

    R.H Smyth wrote a book called "the Horse in Structure and Movement", in it he questioned the fact that modern horses could jump or run the way they do because their conformation and skeletal make-up is not right for such intense competitions and he was surprised that they manage to do it at all. It's worth a read although it's technical. As someone said a horse is not mature until six and yet we run them at two, no wonder they injure themselves even if it is not always fatal. The Northern Dancer influence is almost incalculable.

  • Comment number 24.

    6:arthur daley : The thoroughbred racehorse has been improved to run faster and faster and that takes things closer to the edge of the physiology.

    actually this is not true. racehorses don't run any much faster than they did 40 years ago. the speed has hardly increased. humans on the other hand have made leaps in this area and run much faster.

  • Comment number 25.

    There is no evidence that breeding has caused an increase in breakdowns.
    If you look at the statistics, horses are more likely to meet with a fatal accident racing in the USA than in Britain. The main difference between the two countries is the surface they race on: dirt in the USA and Turf in GB. Also US racing has been permissive of "race day medication" for too long, the only major racing nation in the world to do so. I'd be more concerned about the medications weakening the breed than inbreeding.

    As an aside, Thoroughbreds are bred to mature younger and faster than "ordinary" horses, that is why we can race them at 2. There was research carried out some years ago that suggested the younger you start racing a horse the less likely it was too suffer such an injury. The increased stress on the limbs helped to strengthen bone density. This is why they introduced "Bumper" races for 3 year old "Jumps" horses, which allowed them to race on the Flat at 3, before moving onto hurdle races at 4 or 5 instead.

  • Comment number 26.

    I own 3 racehorses, my oldest is 29 and raced on the track 2 weeks after his 2nd birthday. He raced for 9 years finishing his career when he was 11. He has perfect confirmation. He is kept as a leisure horse and was taken down to the beach for some fun a few years back when he was 21, he was clocked doing 40mph. Because TB only have natural service the number of mares covered is restricted. These injuries occur becuase you are asking a horse to perform at the top of his/her ability but equally also occur in the field or even walking out the stable. If they put their foot down wrong nothing can prevent this. TB are not difficult to look after, look at the hundreds playing polo each year who are quiet as a mouse. We need to make sure that breeding doesn't become something just for the mega studs but also is controlled so there are good homes for them all.

  • Comment number 27.

    re 21

    Decent idea but not sure you can still breed once pumped full of steriods?

  • Comment number 28.

    Having ridden racehorses for pleasure, for many years, I can categorically say they are not genetically flawed. If anything thay present as a tribute to man's ocassional brilliance in stabilising natural selectivity for our needs. The issue is one of greed and poor management, something we are expert in. Too much to soon will break any thorobred machine, and thats just what a racehorse is!

  • Comment number 29.

    The are a lot of contributing factors at work including the age of the horse, the way it has been trained, the differing surfaces they run on and so forth. One comparison I would like to draw on though lies in the training of dressage horses; they do not have the confirmation or strength to carry out high school movements until they reach 7 or 8 years old, and even as a four or five year old may not do any more than walk/trot tests in competitions which begs the question as to whether racing a horse at 2 or 3 is actually a little too early in a horses development.

  • Comment number 30.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • Comment number 31.

    A simple test of whether the in-breeding is a good thing is this:

    Permit horses bred from outside the studbook to be raced alongside thoroughbreds.

    If they aren't as good, no one will want to breed from them. If they are, it will increase the gene-pool.

  • Comment number 32.

    24 Rob

    I can't discuss properly in 400 characters and I doubt you can. But very basically - How do records keep getting broken then.

    It is the native willingness of the horse to try which is the problem. Occasionally the same problem occurs with people in sport. The problem with horses is they can't talk.

    The breeding programme on the turf essentially favours quick maturing characteristics. It is quite different to the old school store horse for National Hunt which has become less prevalent where a long term physical development approach was taken.

  • Comment number 33.

    I am sure that something is wrong with the breeding procedures of thoroughbreds when you consider that practically every horse running anywhere in any country that matters comes at the very least from the Phalaris sire line, and most likely from his paternal line great great grandson Northern Dancer. The current sire line base must be the narrowist since the start of the 18th century. What has happened to Blandford, Hyperion and St. Simon lines, so strong in living memory, and now all but vanished? How on earth was this allowed to happen!

    I am afraid that what has happened is that breeding has become too commercialised, valuing quick returns, with insufficient emphasis on science and the overall strength of the breed. There is nothing new about this, but the trend has become ever stronger in the modern age of fast communications. Stayer has become a negative word. Winning the Ascot Gold Cup has become a positive stigma for a stallion, and heaven help us, even the Derby is going the same way! Where would the breed be today if early breeders hadn't valued staying powers and the ability to win races such as the Derby, St Leger and the Ascot Gold Cup?
    I have no idea what casuses racehorses to break down, but I find the comments of Barnaby Hunter to be most interesting

  • Comment number 34.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • Comment number 35.

    Has The Sun hacked into the BBC to post this highly irresponsible masterpiece of tabloidism?
    " Racehorses Bred To Breaking Point Shocker "
    We read on aghast and saddened until, if like me, we read on until nearer the end and camoflauged by small print,
    So where is the story? Why not jump off the Anti Horseracing wagon Mr Walker and while I'm at it all the others who think its a cruel sport and go play with Killer Whales in the far north.
    A wholly chuckleheaded collection of words, not worthy of the BBC.

  • Comment number 36.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • Comment number 37.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • Comment number 38.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • Comment number 39.

    This is just the type of article the BBC Radio 4 programme More or Less would ask us all to treat with extreme caution, if not ignore. Nine paragraphs about horses breaking legs, next to several paragraphs about a scientific study about inbreeding in thoroughbred horses, more about breaking legs, and difficulties in horse pregnancy. The scientists say that they can find no link between these things in the data they have collected. No numbers are given. Do more horses break legs now compared to the past? Are there more spontaneous abortions? I think not, because if there were, surely the numbers would be quoted. It is just shockingly presenting information with the intention to mislead; and only the author can say why he wants to mislead. In the paragraph about big races in 2018, the use of the word "another" is unforgiveable in the context of the acticle. Educated readers may wonder if the BBC's already-ropey repution can be maintained if this is the level of illogicality, poor analysis and propagandised information it is prepared to disseminate.


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