Kissing Cousins

I began this post months ago and petered out partway through. I thought there was some problem with inbreeding in thoroughbreds but I didn’t have anything other than my own conjecture to back it up, and frankly my know-how of the workings of equine genetics is pretty inadequate so why would anyone want to read my ramblings? Well, my knowledge remains pretty limited, but a poster called amymay at HHO linked to this new BBC piece on releated research. I’ve added highlights to the end of my ramble, but of course you can spare yourself my twittering and skip straight to the report itself!  The original post was triggered by a news item on the trainer of a colt called Big Brown – hence the non-genetic intro.

US racehorse trainer Richard Dutrow Jr has been banned from competing in New York State for ten years. The New York Times reports:

For years, Mr. Dutrow, whose horses have won some $80 million in purses and found themselves in the winner’s circle after any number of premier races across the globe, has been seen by many as the face of much of what is wrong with racing. Mr. Dutrow had been cited for nearly 70 violations at 15 racetracks in nine states — everything from hiding workouts of his horses to using powerful painkillers on horses he ultimately sent out to race.

“New York’s racing industry has no place or patience for Mr. Dutrow,” John Sabini, the chairman of the racing board, said in a statement. “His repeated violations and disregard of the rules of racing has eroded confidence in the betting public and caused an embarrassment throughout the industry.” …

… in 2008, he led Big Brown to victories in the Kentucky Derby and the Preakness Stakes, but he lost the Triple Crown when the colt, after being taken off a steroid regimen, finished last in the Belmont Stakes. At the time, it was permissible to use certain steroids on horses.

I remember Big Brown. I especially remember Fran Jurga’s coverage of his corrective treatment and shoeing before the Kentucky Derby, in which it looked as though his hooves, apparently damaged by hard tracks, had been largely artificially rebuilt. It was an incredible piece of farrier-work but raised some questions in the comments. Did he have poor feet genetically? His connections said he had broken, rather than weak feet. Should he be racing at all with this much damage, or should he be rested until his hoof had grown back? Should he qualify as a stallion with these faults?

He crashed and burned in the Belmont, with connections blaming a lost shoe and a quarter crack rather than the end of his steroid regimen, but afterwards his owner announced that the horses he kept at Dutrow’s barn would  no longer be treated with steroids. As the NYT reported at the time:

‘Two days after the announcement, racing officials in Kentucky disclosed that a horse trained by Dutrow had tested positive for twice the allowable level of clenbuterol, a steroidlike medication that helps burn fat and promotes muscle growth.’

Big Brown won two more major stakes races and retired a little less tarnished to Three Chimneys in Kentucky (although the competition in the Haskell Invitational was “weak” and he won the Grade II Monmouth by only half a length, a far cry from his steroid-driven combined winning margin in the Kentucky Derby and the Preakness – ten lengths) . His first foals will be two-year-olds next year, so presumably he’s been spared the alleged infertility side effect of the steroids, something that afflicted some high-selling colts in the 1980s. As I was on a roll I went to look up his stallion card at the stud’s website, and was delighted to find that the site is every pedigree nerd’s dream. It even has a “hypothetical mating” gizmo that gives you instant pedigrees for the offspring of their stallions and a any thoroughbred mare you choose. But then I clicked on Big Brown’s “mating recommendations”. And, well… Earlier this year I blogged about the effects of “line breeding” on the canine gene pool (something I recommend reading in full here) described in John Bradshaw’s In Defence of Dogs:

Multiple domestications and back-crossing with wolves meant that dogs worldwide still have an estimated 95 per cent of the variation that was present in wolves during the time of domestication. Most of this variation lives on today in street dogs and mongrels, but pedigree dogs have lost a further 35 per cent. That may not seem much, but let us imagine the scenario in human terms. Mongrels maintain levels of variability that are similar to those found globally in our own species. In many individual breeds, however, the amount of variation within the whole breed amounts to little more than is typical of first cousins in our species.

Three Chimney’s advice on potential mates for Big Brown is as follows:

Champion BIG BROWN has a very special pedigree pattern to make a successful sire. Although inbred 3×3 to Northern Dancer via speed sons Danzig and Nureyev, BIG BROWN inherits classic speed from inbreeding to a rare combination of the Damascus/Round Table affinity. His genetic pattern indicates it was no fluke he became a Champion racehorse with clean airflow. Damascus carries the strain of elite mare Perfume II (Badruddin – Lavendula II, by Pharos), a female genetic relative of Nasrullah and Royal Charger. Thus, it makes sense to reinforce the superior mix of Nearco, Blenheim and Mumtaz Mahal with the double of Northern Dancer in BIG BROWN’s pedigree.

BIG BROWN needs mares with a “daughter” of Northern Dancer (especially daughters of More Than Ready or Southern Halo), as they will reinforce superior genes. Mares with Hail to Reason, Seattle Slew, Blushing Groom, and especially Mr. Prospector are ideal test matings. Mr. Prospector will supply a “son” of Champion Native Dancer to any foal sired by BIG BROWN, thus balancing Natalma, “daughter” of Northern Dancer.

So, essentially they are recommending that you “reinforce” the pedigree of Northern Dancer (Nearco was his grandsire, Blenheim his great great grandfather and Mumtaz Mahal his great great great grandmother) – Northern Dancer being Big Brown’s great grandfather twice over. This is, it has to be said, pretty distant cousin marriage, and everyone knows that the thoroughbred gene pool is shallow, but for how much longer can breeders go on “reinforcing” bloodlines? Nearco was linebred to the great St Simon, and he in turn to Voltaire and so on and so forth.

Well, possibly not for much longer, according to the BBC coverage of new research:

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. …

“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. … 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+.” …

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. …

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.”

This, of course, would involve the thoroughbred industry working together to do something that might affect the cash flow and “free market” of the breeding industry – something I can’t quite imagine happening until the breed is beyond the crisis point, cynic that I am…