There’s no rulebook on when a broodmare or stallion should retire. No set age. No hard line. Just a combination of biology, welfare, commercial sense – and common sense.
While retirement from racing is fairly straightforward, retirement from breeding is more nuanced. Some horses stay active into their twenties. Others step away much earlier. It all depends on how they’re coping – physically, reproductively, and commercially.
This piece explores how retirement decisions are made for Thoroughbred mares and stallions, what the science says about aging and fertility, and what life often looks like after the breeding shed.
Stallion retirement: not just about age
Some stallions keep covering well into their mid-20s. Others are pensioned early. The deciding factors usually fall into three key areas:
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Fertility decline: Stallions can produce sperm for life, but quality doesn’t always follow. Studies show a decline in sperm motility and morphology with age.¹
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Physical limitations: Arthritis and age-related wear-and-tear can make the physical side of covering more difficult.
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Market demand: Breeding is a business. If a stallion’s yearlings don’t sell or perform, or a younger version of his pedigree emerges, commercial pressure may push retirement – regardless of fertility.
When Arrowfield Stud retired Not A Single Doubt, John Messara was frank about the reasons:
“Our head vet has advised that Not A Single Doubt is incapable of performing his breeding duties and accordingly he has been retired from active service… We are immensely grateful to him, and he will be loved and cared for at Arrowfield for the rest of his life.”
– John Messara, Arrowfield Stud (2020)
Interestingly, in the wild, stallions tend to retire far earlier. Most lose dominance to younger rivals around 10 to 15 years old. Once ousted, they’re typically forced into bachelor groups or solitary life – a sharp exit with no gentle handover.²
Mares tend to retire younger
Most Thoroughbred mares retire from breeding between 15 and 20 years old, though it’s not uncommon to see exceptions.
The reasons are mostly biological – and sometimes heartbreakingly practical:
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Reproductive health: As mares age, their conception rates drop, while the risk of pregnancy complications increases. Ginther’s reproductive studies show a significant decline post-15.³
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Foaling history: Mares who’ve had difficult pregnancies, abortions, or delivery complications are often retired earlier to protect their welfare.
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Production record: In commercial operations, mares that consistently produce underperforming or unsaleable foals may be retired sooner.
In the wild, mares often continue breeding into their late teens or early 20s, with fertility gradually declining over time. But once their breeding days are over, they typically remain in the herd as matriarchs – steady, experienced figures who offer social structure and safety to the group.⁴
But just because a mare can keep breeding doesn’t mean she should. As welfare expert Jennifer Krawczyk explains:
“You have to look at the horse’s value and their risk of being unwanted… We knew that if a horse came in for retraining over the age of 15 or having had more than a year in the paddock, all of those things contributed to it being very hard to transition them.”
– Jennifer Krawczyk, The Thoroughbred Report (2023)
What else influences retirement?
It’s never just about age. Here’s what else plays a role:
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Economic reality: Breeding is expensive – even more so when dealing with aged or high-risk horses. Owners must weigh cost vs reward.
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Veterinary advancements: Better vet care, scans, nutrition, and monitoring have extended many horses’ breeding careers, especially stallions.
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Individual temperament and history: Just like humans, some horses stay sharp and strong well into old age. Others need to take a step back much sooner.
Life after the breeding shed
Most stallions and mares retire for good once breeding ends. Some remain at the farm they bred from. Others go to specialised retirement properties or return to the original owners who bred or raced them.
But some mares take on a special role:
nannies.
Each year, newly weaned foals are transitioned into paddocks with retired broodmares – calm, experienced older mares who offer social support and maternal presence without the milk. They teach manners, model herd behaviour, and help young horses adjust to life after mum.
Final word
There’s no single answer to when a broodmare or stallion should retire – and that’s a good thing. The best decisions are individual. They consider the horse’s health, fertility, behaviour, and value to the breeding program.
Done well, retirement is not just an end. It’s a transition. And in many good farms, it comes with peace, pasture, and purpose – whether that’s watching the sun set from the hill, or helping raise the next generation from just across the fence.
