The First Heat Breeding Controversy: Science Smackdown - Round Two
By Jennifer Stoeckl, MAT - Dire Wolf Project CEO, Sept. 12, 2025
Apparently, we have ourselves a real live debate going on with one of our esteemed Inner Circle pack members.
That’s totally fine.
We aren’t always going to agree on everything… and the “first heat breeding” topic is especially emotional for some people.
There is a LOT of wrong information out there about it, so the clapbacks make sense.
I don’t blame her, really.
She’s just parroting what everyone says about this topic (including AI).
No one else has the courage to do the actual work it takes to understand the reality behind “first head breeding”, so we might as well.
Get out the popcorn, my friends!
This is going to be fun.
Here’s her reply to yesterday’s Inner Circle email:
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“The claim that breeding on a dog’s first heat is biologically safer is misleading and not well supported by science.
Pelvis & relaxin: It’s true that relaxin increases connective tissue laxity, but there is no evidence that ossification of the pelvis after 16–18 months is the main driver of dystocia. Dystocia is multi-factorial — litter size, fetal size, uterine inertia, and maternal health all play bigger roles (Cornelius et al., 2019
https://www.sciencedirect.com/science/article/abs/pii/S0093691X18307003?). The newsletter’s cartilage “percentages” aren’t backed by peer-reviewed data.
First-heat risks: Breeding at first heat often means breeding an immature bitch. Large breeds especially may not finish skeletal growth until 18–24 months (Hazewinkel et al., 1985
https://pubmed.ncbi.nlm.nih.gov/4055747/). Studies show very young dams are linked to higher neonatal mortality and maternal care issues (Fugazza et al., 2022
https://www.mdpi.com/2076-2615/12/11/1402?).
The “2.4× dystocia risk after 2 years” statistic: Yes, one Norwegian Kennel Club study reported this (YMAWS, 2016
https://cdn.ymaws.com/www.therio.org/resource/collection/15B4140C-971B-43C7-8A6A-3F58C08B71BE/2016_v3_035.pdf?). But correlation ≠ causation. Older first-parity bitches may have larger fetuses, smaller litters, or reduced uterine contractility — not simply “ossified pelvis.”
Veterinary consensus: Most reproductive specialists recommend breeding at full maturity (often second heat, ~18–24 months for large breeds), which balances the risks of immaturity with those of delayed parity.
Bottom line: First-heat breeding is not proven safer. You have people here in the inner circle that are scientists, Veterinarians breeders themselves and have been longer than you've been alive and yet you are rude to those that challenge your misunderstanding of the scientific studies. Do better.”
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Well, there you have it.
Someone who apparently knows much more than I do.
I wonder how many “first heat litters” she’s bred in order to know so much.
(Oh, wait… she wouldn’t dare!)
Well, if she doesn’t have any real “first heat breeding” experience, I wonder how many litters she’s bred over her entire lifetime.
My guess is not nearly as many as I have, if any at all.
But, that’s fine.
I’ll play along with her arguments.
Let’s take her claims one at a time and see where we end up.
Maybe she’ll make a “wait to breed” convert out of me, yet.
And I’ll join the ranks of the “responsible breeders” out there who understand just how harmful it is to breed the way nature has since life began on this planet.
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“The claim that breeding on a dog’s first heat is biologically safer is misleading and not well supported by science.”
Huh… yesterday, you said that science didn’t back this statement at all, but today your saying that it’s not well supported by science.
Which is it?
You also originally said that my information was concerning, but now its merely misleading.
That’s quite the walk back.
Yesterday, I presented research that supports my claims, so clearly not everyone in the scientific community agrees with your version of support.
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“Pelvis & relaxin: It’s true that relaxin increases connective tissue laxity, but there is no evidence that ossification of the pelvis after 16–18 months is the main driver of dystocia. Dystocia is multi-factorial — litter size, fetal size, uterine inertia, and maternal health all play bigger roles (Cornelius et al., 2019...).”
It sounds like you’re playing semantic dodgeball here by demanding that somehow I’ve claimed that ossification (bone formulation) is the main driver of dystocia (difficult birth).
Nobody is claiming ossification of the pelvis is the lone, or even the main, cause.
It’s definitely a mechanical factor, though.
More ossified bone = less cartilage for relaxin to act on = less functional widening.
That’s a mechanical difference that can turn “easy whelp” into “stuck pup.”
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“The newsletter’s cartilage ‘percentages’ aren’t backed by peer-reviewed data.”
Nice pedantic nitpick you have there.
That’s why I said they were rough estimates.
The underlying anatomical fact remains, however, that juvenile pelvises have substantially more cartilage and growth-plate tissue than ossified adult pelvises.
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“First-heat risks: Breeding at first heat often means breeding an immature bitch. Large breeds especially may not finish skeletal growth until 18–24 months (Hazewinkel et al., 1985...).”
This is my entire point.
Thanks for making it for me.
The sexually mature canine, while able to breed, is still skeletally immature.
And my claim is that very fact aids in a generally easier birthing experience.
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“Studies show very young dams are linked to higher neonatal mortality and maternal care issues (Fugazza et al., 2022...).”
Wait a minute.
Weren’t we just talking about pelvic mechanics and dystocia?
You just lobbed in maternal behavior and mortality as if they’re the same thing.
They’re not.
Maternal care is complex.
It is influenced by genetics, experience, handling, and environment.
And it is not proven whatsoever that first-heat breeding intrinsically produces worse maternal behavior simply due to a dam’s age.
For the sake of this particular argument, let’s just ignore this little red herring, shall we?
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“The ‘2.4× dystocia risk after 2 years’ statistic: Yes, one Norwegian Kennel Club study reported this… But correlation ≠ causation. Older first-parity bitches may have larger fetuses, smaller litters, or reduced uterine contractility — not simply ‘ossified pelvis.’”
I seem to think I’ve seen this point somewhere before.
Now, where was it?
Hmmm…
Oh yeah!
When you said, “…there is no evidence that ossification of the pelvis after 16–18 months is the main driver of dystocia.”
Once again, nobody is claiming ossification of the pelvis is the sole, or even the main, cause.
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“Veterinary consensus: Most reproductive specialists recommend breeding at full maturity (often second heat, ~18–24 months for large breeds), which balances the risks of immaturity with those of delayed parity.”
Here it is in all its glory, folks!
Ye ol’ “appeal to authority” logical fallacy.
It never fails to appear somewhere in the “wait to breed” model argument.
So, let me be VERY clear for those in the back…
The Dire Wolf Project™
fundamentally outright rejects
the “wait to breed” model.
I don’t care if the entire world is against us, which sometimes it feels is the case.
This is NOT how nature operates.
Wild and feral animals breed when natural urges present themselves, regardless of your or anyone else’s feelings.
And the Dire Wolf Project™ follows nature’s example laid out by the creator who sustains all of life.
So, I don’t give a hoot about veterinary consensus.
The majority of vets in this country agree that highly processed artificially fortified kibble is healthy for your dog, too.
Whatever you do, please don’t believe that little bit of veterinary consensus.
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“Bottom line: First-heat breeding is not proven safer. You have people here in the inner circle that are scientists, Veterinarians breeders themselves and have been longer than you've been alive and yet you are rude to those that challenge your misunderstanding of the scientific studies. Do better.”
Not proven safer?
Oh yeah, because the Dire Wolf Project’s hundreds of perfectly safe and easily birthed first heat litters versus a larger degree of difficult post-ossification litters that suggest otherwise simply can’t be enough proof.
What could we possibly know, right?
After all, we aren’t white-coat scientists or veterinarians, so our work mustn’t count.
I get that your belief in “authority” is strong.
As you probably can tell, I completely disagree with your perspective considering I’ve done the actual breeding to know, but disregarding well-documented natural animal behavior is harder to do.
Wild wolves breed on their first heat cycle, too, it just happens to be a wild reproductive system instead of a domesticated one.
I lay out all of the truth behind wild wolves compared to domesticated dogs in the Dire Wolf Project book I wrote in 2018, which is where you can find my fully fleshed out argument on “first heat breeding.”
The Dire Wolf Project has done what no one else has dared:
Safely breed first-heat females under the guidance of expert hands; seeing, time and again, easier first and subsequent births compared to post-ossification whelping.
We did not reach these conclusions by guessing, theorizing, or parroting secondhand opinions.
We reached them by decades of careful, data-driven practice.
We have tracked, recorded, and refined our work in detail.
That is something no critic who refuses to touch first-heat breeding can ever truly refute.
Our pack is carving a new trail across the ice, and the tracks are clear for anyone with courage enough to follow.
The Dire Wolf Project™ stands not just as a dog breeding program but as a living experiment in pushing canine husbandry toward a higher, evidence-based standard.
We will not apologize for doing the work others fear.
We are the future, and we will keep leading until the entire dog world catches up.
Jennifer Stoeckl is the co-founder of the Dire Wolf Project, founder of the DireWolf Guardians American Dirus Dog Training Program, and owner/operator of DireWolf Dogs of Vallecito. She lives in the beautiful inland northwest among the Ponderosa pine forests with her pack of American Dirus dogs.