COAT COLOUR INHERITANCE

Article by Tony Morris

Tony Morris will contribute monthly features to www.juddmonte.com. If you have a query relating to historic events, horses or racing personalities, or want his view on any aspect of Flat racing and breeding, past or present (with the exception of advice on matings), write to tony.morris@mail.com with your request.

This month’s feature is prompted by a message from Simon Morton of the West Midlands.  He was told that there had been a parade of ten foals from FRANKEL's first crop at Banstead Manor recently and that four of those shown – two of each sex – were chesnut in colour.

Having always understood that bay dominates chesnut, and being well aware that FRANKEL is himself bay, Simon wonders how it is that the great Juddmonte champion can sire chesnut progeny.  He asks: “Who gave those four foals their chesnut coats?”

The short answer is FRANKEL.  Or, more precisely, he provides half the answer in each case.  The apparent conundrum is readily explained now, though for the first two centuries of the thoroughbred’s existence as a distinct breed, the question must often have been asked about a host of horses, and there was then no definitive solution.

It took a whole new branch of science, labelled genetics by a Cambridge academic called William Bateson, to demonstrate the key facts about inheritance as the reign of Queen Victoria was coming to an end.  The vital clues had been provided in a speech delivered in 1865 by an Augustinian monk named Gregor Mendel whose researches were in the field of plant hybridisation.  It seems unlikely that anyone who heard that lecture was able to grasp its significance, because it was soon forgotten.  

Mendel himself had long been dead before a botanist called Robert Allen Rolfe came across some papers left by the Moravian monk, found that their contents tallied with conclusions he had drawn from his own researches, but had been unable to confirm.  At a conference in London in 1899 Rolfe gave a talk in which he drew attention to Mendel’s work and particularly noted his use of the terms ‘dominant’ and ‘recessive’ which served to explain the formerly inexplicable.

What had thoroughbred breeders discovered about coat colour inheritance through their own observations over the previous 200 years?  Not a lot, in truth.  They had noticed that when they mated a chesnut with a chesnut, the offspring was invariably chesnut.  And they knew that to obtain a grey foal one of the parents had to be grey.  But there were plenty of chesnuts whose parents were not both chesnut, and the use of a grey parent did not always result in a grey product.  There were also some bay or brown horses who were apparently incapable of getting chesnut offspring.

One small-time breeder and writer on thoroughbred matters, R.H. Copperthwaite, had opinions on the parentage of Thormanby, chesnut winner of the 1860 Derby and the Gold Cup of the following year.  The colt’s dam had been covered in 1856 by both Melbourne and Windhound, so he was described as by ‘either or’ in the General Stud Book.  Copperthwaite was adamant that Windhound was Thormanby’s true sire, and some of his reasons might well have been disputed, but he had correctly noted that Melbourne had never sired a chesnut foal, so he could feel he was on safe ground in plumping for Windhound. His speculation was spot on in that case, but neither he nor anyone else could have provided solutions to all the other mysteries until the rediscovery of Mendel’s work and the significance of dominance and recessiveness was fully appreciated.

It should never be forgotten that it was the thoroughbred, most specifically the evidence gleaned from the first 20 volumes of the General Stud Book, which was crucial in establishing genetics as a new branch of science.  What its proponents needed was a reliable record of a breed compiled over a long period.  In Britain a legal requirement for registration of births in the human race came into force as recently as 1837, whereas such documentation had a much longer history in the thoroughbred.

Establishing the facts about dominant and recessive characters was vital if Mendel’s theories were to be proved and the new science were to gain acceptance.  William Bateson and his followers felt sure that the General Stud Book held the solution, and that coat colour in the thoroughbred was the specific area which would deliver the required proof.  What they needed was more Melbournes – examples of bay or brown horses who produced no chesnuts – and confirmation that there was no exception to the rule about a chesnut always resulting from the union of two chesnuts.  The opposition camp, led by Bateson’s deadly enemy, Raphael Weldon, would not concede while there were anomalies.

Of course, this was a row between scientists, taking place without the knowledge of practical horsemen, and it seems extraordinary that none was ever consulted while the rival factions warred.  A year passed without a resolution of the most serious anomaly in the General Stud Book – the registered chesnut Ben Battle had died in 1894 at the end of a long stud career in which he had sired many bay or brown foals out of chesnut mares.  Any number of breeders who had used the stallion might have resolved the issue if they had just been asked, but they were not drawn into the argument.  

It was not until 1906 that one of the Bateson camp, Charles Chamberlain Hurst, got around to consulting the Racing Calendar, when he discovered that throughout his career on the racecourse Ben Battle had been described as brown.  That revelation provided the final proof of Mendel’s theories; Ben Battle’s colour dominance was established, and within months Raphael Weldon died, a broken man at the age of 46.

We have come by a circuitous route, but here is the answer to your question, Simon.  FRANKEL, like every other thoroughbred, has two genes coding for colour.  One is bay, expressed conspicuously in his own coat, and the other is chesnut.  He has transmitted his chesnut gene to those four foals, who also received a chesnut gene from their dams.  As for those six bay foals, we can only be certain that FRANKEL supplied his bay gene if the dam is herself chesnut.

While the matter of coat colour inheritance was a crucial factor in establishing the science of genetics, and can still seem fascinating to some, we should never forget that it matters not one jot where racing ability is concerned.  While it may seem impressive that such as Sadler’s Wells, Danehill, Montjeu, DANSILI and OASIS DREAM have carved out successful stud careers while getting only stock of the same colour as themselves, it signifies no more than that they couldn’t help it.  With two bay genes, they had to transmit one.  And there have been many bad sires who were pure-breeding bays.

FRANKEL can’t help getting his quota of chesnuts.  And he will be none the worse for it.  While there is no doubt that FRANKEL is the best son of Galileo and the same colour as his sire, we also have to remember that the Coolmore colossus also has three chesnut Derby winners in New Approach, Ruler of the World and Australia.  
    
Tony Morris has been writing about racing and breeding for over 50 years, contributing to numerous publications at home and abroad. He is the author or co-author of several books, was named Racing Journalist of the Year in 1990, and in 2010 received the TBA's highest award, the Devonshire Bronze, for his 'outstanding contribution to the British breeding industry. He has travelled widely, attending race meetings and bloodstock sales in various countries, and has been privileged to see many of the best horses and meet many of the most prominent personalities in the industry over the last half-century. 

Date: 1 August 2014