The internet loves a good outrage story, and when it comes to horses, the image of a mare being forcibly bred is ripe for moral panic.
But here’s the thing: breeding doesn’t have to be stressful. And in well-run operations, it generally isn’t.
Despite assumptions that Thoroughbred breeding is some kind of high-stress gauntlet for mares, the science, and those working quietly behind the shed doors, say otherwise. Yes, stress can occur. But no, it’s not inevitable. And more importantly, there are proven, routine ways to prevent it.
This isn’t about romanticising the breeding shed. It’s about getting real on what actually causes stress in mares, how it shows up, and what good management looks like when animal welfare is genuinely the priority.
Stress happens, but not always the way you think
Stress in animals tends to fall into three camps: physical, physiological, or psychological.
For broodmares, here’s how that might play out:
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Physical: The rigours of pregnancy, birth, and recovery; and, in the case of Thoroughbreds, live cover (required by breed rules) can cause discomfort if not handled with care.
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Physiological: Hormonal changes during the reproductive cycle can affect behaviour, especially if a mare isn’t in optimal estrus.
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Psychological: New surroundings, the presence of a stallion, or heavy-handed handlers can create unnecessary tension.
But identifying these stressors isn’t about doomscrolling. It’s about designing systems that minimise or eliminate them entirely.
The science backs better practices
Multiple studies have measured stress levels in breeding mares using cortisol (the hormone released when animals are stressed) as a biomarker. And the stress response isn’t universal.
A 2015 study by Dr Christine Aurich found that inexperienced mares showed higher cortisol levels during breeding, but this wasn’t the case across the board. Acclimatised mares handled the process with significantly less physiological stress.¹
Renowned equine reproductive scientist Dr O.J. Ginther also noted that when teasing (the process of exposing a mare to a stallion to assess readiness) is done calmly and with care, it actually reduces risk – ensuring covers only occur when mares are truly receptive.²
And it’s not just academics saying it.
“Good breeding starts with a calm mare. If she’s stressed, you’re already losing ground.”
– Dr Charlie El-Hage, Victorian Chief Veterinary Officer³
“Welfare is central to breeding success. You can’t force a horse to do anything well under stress, and you shouldn’t want to.”
– Rick Jamieson, Gilgai Farm (breeder of Black Caviar)⁴
What actually causes stress?
Let’s get specific. Stress in mares is often a management issue, not a moral one. Here’s where it can go wrong:
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Poor handling: restraint without understanding equine behaviour causes fear, not cooperation
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Chaotic environments: loud, unfamiliar spaces can spook even seasoned mares
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Breeding out of cycle: trying to cover a mare not in season leads to resistance and discomfort
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Underlying health issues: injuries, infections or undetected pain can exacerbate the experience
Some argue that if mares were left to breed “naturally,” it would be less stressful. But “natural” doesn’t always mean kind.
In the wild, mares breed within herds, typically selecting the dominant stallion. But that process is far from tranquil. Stallion competition can be fierce. Mares are often chased, guarded, and covered multiple times each cycle. Environmental pressures – from food scarcity to threats from other stallions – only add to the load. Studies of feral horse populations have shown elevated stress levels during the breeding season due to these exact pressures.⁵
There is no utopia – in the wild or the breeding shed. But there is a difference between unmanaged stress and well-managed welfare. In domestic breeding, horses are monitored, protected from injury, and offered veterinary care, pain relief, and soft footing. They are not left to the mercy of weather, predators, or herd violence. And that makes a world of difference.
So what does good practice look like?
You won’t find it in clickbait videos, but here’s what happens behind the scenes at well-run breeding farms:
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Gentle, experienced handlers use calm voices and minimal restraint
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Gradual introductions to the breeding shed reduce fear and promote confidence
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Veterinary tracking of hormonal cycles ensures breeding happens at the right time
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Environmental control means clean, quiet, well-lit sheds with familiar routines
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Post-breeding care ensures any discomfort is promptly addressed
These aren’t luxuries — they’re standard practice in any responsible Thoroughbred breeding operation.
Final word
Breeding a Thoroughbred mare should not be a battleground. And when done properly, it isn’t.
Stress in horses is real and must be respected – but it is also something that skilled horsemen and women mitigate every single day. Not with heroics, but with routine care, quiet systems, and decades of learned horsemanship.
Let’s be clear: if a mare is stressed during breeding, that’s a management issue, but not an industry default.
And in this space, excuses don’t fly. Only facts do.
