The genetic palette: The science behind coloured horses’ coats *H&H Plus*

A splash of colour is nothing new in the show ring, where skewbalds and piebalds regularly grace the line-up. Neither does a coloured coat come as a surprise at the lower dressage levels, as traditional gypsy cobs continue to make their mark. But patches of white on a performance horse can really turn heads. With implications of heavy breeding, a coloured coat pattern tends to be more closely associated with pulling a cart than achieving a podium place. Are these elite equine athletes really on a par with their plain-coated counterparts? According to Dr Samantha Brooks, associate professor of equine physiology at the University of Florida, most white “spotting” patterns in the horse – the patches on our skewbalds and piebalds – are caused by just one change in a single gene. [subscriber-content]“The frequencies of these patterns do tend to differ by breed, but that’s not a consequence or effect of the breed – just a result of either selective breeding or the closure of the breed registry,” says Samantha, explaining that the exclusion of white markings by certain breed societies and studbooks has seen these variations die out. “Spotting patterns are common in breeds such as gypsy horses and American paints, and are rare – but not impossible – within continental warmbloods and the thoroughbred. The pattern impacts only the pigmentation, however, and is entirely independent of athletic traits. “Most breeds of horse have naturally spotted individuals, even in cases where the breed registries select against spotting,” she adds. “In the thoroughbred, for example, there are several spontaneous white spotting patterns that emerged as random mutations within the breed, generating coloured horses of 100% thoroughbred ancestry.” So why is there a tendency to associate colour with a lack of athleticism? “This probably derives from the frequency of these alleles [a gene that determines hair colour, for example] in ‘heavy’ horse groups, versus ‘light’ horses,” says Samantha. “Warmblood sport horses are commonly a mix of balanced and durable heavy horse lines with light and fast thoroughbred and Arab lines. Getting this mix right is quite tricky: too much light horse and they can be prone to injury and behavioural challenges, too much heavy horse and they lack brilliance and speed. It’s easier to get a spotting gene from a heavy horse group, as the frequency within those populations is higher,” she adds. “So we’ve learned to stereotype a coloured coat with heavier ancestry and, therefore, a lack of athleticism.” Samantha points out that this association is misleading, not just because colour has no direct impact on athletic performance. “The presence of just one spotting gene is not a strong predictor of the proportion of heavy horse ancestry,” she says. “Indeed, pedigree information is at best an estimate of such ancestry and can differ from an individual’s actual genetic make-up by large margins. The only way to measure the proportion of heavy horse ancestry in a sport horse is by using commercially available genetic tests that employ thousands of genetic markers and large reference populations. “Depending on the source of the spotting allele and the level of focus within a breeding programme, it is not difficult to breed coloured sport horses that have very comparable genetic backgrounds to their less flashy compatriots – including genes contributing to performance.” Coloured patterns While there shouldn’t be any direct effect of a coat colour gene on performance, there could be a linked effect – as Dr Stephen Harrison of Thoroughbred Genetics explains. “A certain colour gene could be co-inherited in a block with other genes that are characteristic of a certain breed or horse type,” he says. “These colour genes may have been selected where there is also a preference for other more conformational characteristics, such as length of cannon bone in Paso horses. “Co-selection of different genes is then difficult to separate, because they’ve been bred in over a number of generations,” adds Stephen. “Similarly, non-selection of a coloured coat, but selection of other features may inadvertently ‘fix’ colour in a non-performing type, such as the cart horse. “Other observations are worth making,” he adds. “Chestnut coat colour needs to be homozygous recessive, so to achieve this there probably has to be a higher degree of inbreeding. Inbreeding levels do affect performance, so, while the gene itself may have no effect, the method of arriving at the colour may have.” Stephen says the reason we very rarely see coloured patterns in thoroughbreds is most likely because people don’t like the colour. “There’s probably social prejudice, maybe derived from their working backgrounds or even as their role as horses that the ‘Indians’ rode in cowboy and Indian films,” he says, adding there are also disproportionately few greys in racing. “It would have been easy enough to breed the colours in over the course of 500 years, if there was a demand.” Stephen explains that the only viable way of breeding a coloured “pure” thoroughbred would be to introduce the coloured pattern through a breed or type not too distant from thoroughbred or performance horses, such as the Selle Français or AQPS (autre que pur-sang, or “other than thoroughbred”). “These are near enough thoroughbred, but more like National Hunt types,” he says. “Any horse that was registered could be done through the half-bred studbook. It would be very difficult to ‘purify’ the non thoroughbred linked genetic aspects to a level that would allow competition in top-quality Flat racing, but it might be more realistic in jump racing, showjumping or dressage, where flat-out speed is not the absolute determinant of success and where other factors come into play. “It would be relatively easy to select a sport horse that was both coloured and proficient, over a reasonable time frame,” he adds. “Remember, though, that the thoroughbred or thoroughbred-type has been bred for centuries, and even then there is quite a lot of variability in the breed. It would take a long time to breed out other non-thoroughbred characteristics co-inherited with any coat colour newly introduced.” A lack of demand With a relatively slim choice of breeding material, the odds are stacked against producing a coloured sporting icon. Yet without such a trend-setter, lack of demand keeps the breeding pool limited. It’s something of a chicken-and-egg situation. “There simply isn’t a role model at the top of dressage,” admits breeder Rosalyn Serex of Solaris Sport Horses. “We’re still looking for the next star at that level in the dressage arena; there’s still a lot of work to do. “But the jumping gene pool is now fantastic,” she adds, referring to influences such as Limbo, the Concorde-sired coloured stallion whose offspring include former French showjumper Visage Van De Olmenhoeve (now Coppabella Visage). “It is possible to breed for both colour and performance.” Rosalyn outlines some of the challenges – such as the belief that coloured dressage horses are difficult to judge, because their markings distract the eye, and being able to place a promising youngster in professional hands. “People are definitely producing the quality, but these horses are not necessarily purchased by top riders,” explains Rosalyn, who moved from a sport horse background into the coloured route and found a “niche market”. “Many go to amateur homes.” Nevertheless, breeders continue to aim high. Successful Solaris coloured stallions have included Umenno and his home-bred son Buenno – both of whom have Samber in their bloodlines. Buenno’s progeny include Solaris Fechinna, who has showjumped professionally, and a colt out of Tiger Lily IX, who evented with Zara Tindall. Coloured filly foal Orijanna SSH, by dressage stallion Imposantos and out of KWPN Ster mare Jaffa Caxe SSH, scored 8.1 points at the UK Elite Foals registration tour last year. Finding a coloured champion is also a long-held ambition for Olympic showjumper John Whitaker. “It’s nice to have something a bit different,” reveals John, whose obsession started with a “good coloured pony” he had as a 14-year-old boy, called Crazy Horse. “I’ve had coloured horses all my life and I’ve bred one or two, but I’m still looking for that special one. “When you’re considering a showjumper, though, colour is the last thing on your mind,” he adds. “The main thing is the jump, along with the right temperament and the ability to cope with pressure. If you start with colour, you won’t get very far.” A notable success was Utah Van Erpekom, with whom John won internationally, and Nureev, who was jumped by his daughter, Louise. John had particularly high hopes for another strikingly coloured Limbo son, Nepos Van Limbo. “He did a Nations Cup with my son Robert and looked like one that would go all the way, but sadly he died from colic at nine,” says John. “We also had a really fancy coloured two-year-old my wife and Robert bought me as a Christmas present. Joanne [John’s daughter] later qualified him for the Horse of the Year Show Foxhunter final and we eventually sold him, but we kept some semen. “Good horses are few and far between, so to get a coloured one that’s an absolute superstar is one in a million,” he adds. “But there’s no reason there shouldn’t be more about; we just need a few more enthusiasts, like me. I’ll keep trying.” King of colour Almost every successful coloured sport horse can trace his ancestry back to Samber. The prolific sire, who was by the British-bred thoroughbred Pericles and out of black tobiano mare Tina D, became the only coloured stallion to be approved by the KWPN stud book. “My uncle Hendrik bought Samber because nobody else wanted a horse of that colour,” says Jannemiek Vrieling, sister of showjumper Jur, explaining that the Dutch-bred stallion scored a maximum 10 for character at his 100-day performance test. “I was just 14 when I competed him in dressage and showjumping, but he was so easy to handle. He loved small children and cuddles; his temperament was amazing.” Samber reached grade A equivalent in showjumping and was taken to grand prix by Dutch dressage coach and judge Monique Peutz. Dubbed “the king of the coloured horses”, he was still breeding into his old age before he died in 2009, aged 33 – leaving thousands of coloured warmblood descendants worldwide. Ref Horse & Hound; 25 June 2020 [/subscriber-content]