Bloodstock Briefing - examining the sire lines which are no longer popular and asking what has caused their demise?

Article by Jordin Rosser

The first breeders of the modern-day thoroughbred had imported 197 Middle Eastern stallions to breed to their English mares in the 17th and 18th centuries, but only three of those stallions’ sire lines are present today – the Darley Arabian, Godolphin Arabian and Byerley Turk (1). Of these three foundational sire lines, the Darley Arabian has dominated the bloodstock industry, with both the Godolphin Arabian and Byerley Turk sire lines having dwindled in number. Even with the abundance of the Darley Arabian line, there are branches in this foundational sire’s line which have been lost or are endangered.

To discover why these sire lines are disappearing, we must look at the thoroughbred breed on a global stage. We have gathered pedigree analysts and breeders from Europe, United States, and Australia to examine the less popular sire lines and what factors caused their demise. Suzi Prichard-Jones (the author of Byerley, The Thoroughbred’s Ticking Time Bomb and founder of The Byerley Turk & Godolphin Arabian Conservation Project) and Alan Porter (a pedigree analyst for Pedigree Consultants LLC and co-creator of TrueNicks) are pedigree experts from Ireland/United States and United States, respectively. John Messara (the founder and owner of Arrowfield Stud in NSW, Australia), David O’Farrell (the operations manager of Ocala Stud in Florida, USA), and Kirsten Rausing (the owner and operator of Lanwades Stud in Newmarket, England) are breeders whose high profile, highly successful, stud farms are shaping the landscape of the thoroughbred breed. 

Q: Why do you believe the Godolphin Arabian and Byerley Turk sire lines have become less prevalent? 

The pedigree analyst panelists weighed in with a history of these three foundational sires, explaining how the first champion progeny sires, born in the mid-1700s, are a coordinated blend: Herod (Byerley Turk sire line – Darley Arabian mare), Matchem (Godolphin Arabian sire line – Byerley Turk mare), and Eclipse (Darley Arabian sire line – Godolphin Arabian mare). 

These champion sire lines dominated the breed utterly until the 20th century.  The beginning of the fall of the Godolphin Arabian line in America, most recognizable as the Man O’ War line, occurred around World War II when a tremendous number of horses were being imported from Europe. 

Alan Porter mentions, “at that point, European horses were just better – dirt, turf, any surface. They swept aside the North American sire lines”. Furthermore, Porter mentions “for a 36-year period (from 1939 – 1974), with the exception of 5 times, a European stallion or son of a European stallion was the leading sire in America”- giving scale to the domination of the European imports in American pedigrees. 

During this period, Northern Dancer dominated the global bloodstock due to the mixture of American pedigree and European (specifically Darley Arabian) sire lines. Suzi Prichard-Jones believes the Byerley Turk and Godolphin Arabian lines dwindled for a different reason: Temperament. The Byerley Turk horses are very intelligent and high-spirited where the Godolphin Arabian horses are tough, hardy, and determined. These characteristics, Prichard-Jones explains, require a lot of time and patience which often leads to gelding the colts, thereby ending their chance to continue the sire line. 

Q: Given the dominance of some Darley Arabian sire lines over others and the shrinking of the Godolphin Arabian and Byerley Turk sire lines, what impacts on the breed do you expect if these sire lines disappear? 

One of the pedigree analyst panelists, Suzi Prichard-Jones, spoke extensively on this topic. She theorizes the Thoroughbred breed’s success relies on the “balance” between the three foundational sire lines. Due to at least one other foundational sire line being found within the first six generations of every modern Thoroughbred, she believes the traits of the Godolphin Arabian and Byerley Turk are maintaining the breed to be “fit for purpose”. 

Prichard-Jones speculates if these two sire lines disappear, Thoroughbreds will be “fast but heartless horses” due to the spirit, temperament, toughness, and hard-headedness characteristics the two sire lines bring. However, we truly do not know what impacts the narrowing sire lines will have as there has been insufficient genetic research available to produce future breed projections. 

Q: Does the bloodstock industry place more importance on results in the sales ring or results on the racetrack – particularly involving selection of sires or predicting future success of sires? 

Many panelists agreed: most of the market will select only sires whose progeny there will be a market for. Alan Porter mentions, “other than a few very high net worth individuals, a higher proportion of breeders, particularly in the US, are breeding with the expectation of selling” – dictating the change in the bloodstock industry from mostly “breed to race” operations to breeders providing a sustainable sales model. 

The panelists concur that the market believes when selecting stallions for breeding mares, the stallion’s own results on the racetrack matter first, then the narrative changes to the sire’s progeny performance after the first few crops. 

John Messara follows this approach and states he “is more interested in athletic performance and believes results in the sales ring will follow racetrack success”. He also mentions that Japan’s current model of breeding, by breeding the high performers with other high performers, has brought significant success on the track across the globe – giving much credibility to their methodology. 

However, there are also instances of the opposite, as there are a few examples where “stallions can give progeny better than themselves”, as mentioned by Kirsten Rausing, in reference to stallions such as Danzig, who raced only 3 times in his career and is a sire of champions.  This phenomenon is rare however, as the success rate of Danzig’s progeny provide a counterpoint to the conventional wisdom.

Q: How do we attempt to preserve unpopular sire lines or prevent narrowing the genetic pool of the breed? 

Fortunately, there are a few tactics to help: global shutting of stallions and importing stallions to allow for outcrossing. Outcrossing, a practice that brings in “new blood” to the region’s bloodstock, typically crosses stallions who are progeny of successful stallions in other geographical regions and/or stallions that do not have any inbreeding within four generations with a chosen mare. 

David O’Farrell of Ocala Stud says he is “a big believer of the outcross and not afraid to breed to certain sire lines that may not be as fashionable”. Ocala Stud is known for having stallions intended for outcrossing to local mares – many of their success stories include Girvin, Kantharos and the up-and-coming Win Win Win. Similarly, Kirsten Rausing’s Lanwades Stud has had success in “offering breeders and broodmare owners something outside of the ordinary” and a stallion who will “complement the mare population of Europe” including their current stallions Study of Man and Bobby’s Kitten. 

Over the years, the industry has seen how the importing of stallions has strengthened the breed to perform well on the racetrack and in modern times, particularly in Australia and Europe, the practice of shuttling of stallions is proving to have similar results. 

Through all these discussions, some panelists mentioned a glimmer of hope for the Byerley Turk, Godolphin Arabian and endangered Darley Arabian sire lines. There are multiple examples of sire lines coming back from the brink of extinction – a few favorites from the panelists include Fappiano’s Cryptoclearance line reemerging with Candy Ride (ARG), Nasrullah’s Caro line resurging with Uncle Mo, and the most successful story: Storm Bird’s Storm Cat line with 5-time American leading general sire Into Mischief. Each of these resurgences occurred after the use of the outcross technique, leading to future successful stallions and breathing new life into their sire lines. 


Prichard-Jones, Suzi. “The Thoroughbred’s Genetic Cocktail”. Chart. Suzi Prichard-Jones: The Byerley Turk & Godolphin Arabian Conservation Project. Suzi Prichard-Jones, 2021. https://suziprichard-jones.com/the-byerley-turk-godolphin-conservation-project/, 04/01/2024.