Let’s talk Terminology

It’ll be breeding season (MY FAVORITE SEASON) again before we know it. Stallions are already being picked, semen is already being purchased, and plans are already being solidified. Last year I had a lot of people ask me to write out some terminology, since those who are not involved in the breeding world might not have heard some of the terms or abbreviations used. I tend to forget that when I’m writing. So here’s a basic explanation of some of the breeding terminology or abbreviations that you might see, and hopefully we can use this as reference later on. If you think of anything basic that I missed please let me know and I’ll add it!

“by” vs “out of

You will often see this written as Foal by Stallion out of Mare, although a common blunder is for people to use the “out of” part in reference to the stallion. Trust me, foals do not come out of stallions. Physics would not allow it. So “by” = the sire, “out of” equals the dam. E.g., Presto is by Mighty Magic out of Westbound.

stud vs stallion

This one can be a little cultural. In Europe and in sporthorse breeding in general, a “stud” is a farm where stallions live and breed. Western culture and general societal slang has kind of taken the word stud and used it in place of the word stallion. In the sporthorse world though, you would always refer to the stallion as “stallion”, not “stud”, since stud denotes a place. E.g, Hyperion Stud.

half sibling

In the horse breeding world, the term “half sibling” only applies to horses out of the same dam but by different sires. Horses by the same sire but out of different dams aren’t generally referred to as being related, or if they are they’re called “paternal half siblings” (or as I like to call it, “brother from another mother”). E.g. Presto and Manny are half siblings.


ET, in the breeding world anyway, stands for embryo transfer. In this procedure Mare A (known as the donor mare) is bred to Stallion, and the resulting embryo is harvested from Mare A and transplanted into Mare B (known as a recipient mare) to carry to term and foal out/raise. Although it incurs a lot of additional expense, there are several reasons that people might choose this procedure. Perhaps they have a performance mare that they don’t want to take out of sport for a year and a half to have a foal. Perhaps they want to get more than one foal from a mare per year. Perhaps the mare is unable to safely carry to term, or the owner doesn’t want to risk her during foaling. Some people even freeze harvested embryos from exceptional mares and offer them for sale. E.g. We are expecting two full siblings in 2021, by Faustino de Tili out of Chanel, one of which is an ET. (note: even if the biological dam of the offspring did not actually carry and foal the offspring herself, you would still say “out of” as the proper vernacular when referencing the biological dam).

Due Date

I try to explain this a little every year in the Baby Bets contest, but horses don’t actually have due dates the way humans do. The average gestation for a healthy foal can be anywhere from 320 days to 380 days. Viable foals can still be born earlier or later than that range, but that is the range that’s considered typical. The average gestation per a study in Northern Europe was 340 days, so that’s what has been widely accepted and used to calculate a loose “due date” (which isn’t really a due date at all) for horses. Obviously though, this can vary by weeks or even months. I know someone who had a healthy foal born at 309 days of gestation, and I know someone who had a healthy foal born at 396 days gestation. E.g. Y’all see why breeders have come up with things like milk testing to help predict foaling rather than just relying on averages to calculate due dates?

foal shed

Foals are born with a fluffy foal coat that they generally start shedding around 3 months of age. With many horses the coat that shows through underneath after this first “foal shed” will be darker (sometimes much darker) than the eventual adult coat. This is especially true of a lot of chestnuts – often they will look very dark, even liver chestnut, during and after their foal shed. You always see a rash of “LOOK AT MY LIVER CHESTNUT FOAL” posts on social media in the summer time, from people who don’t understand this. Dark brown can sometimes look black in this shed, too. The foal shed can be misleading when it comes to showing the horse’s adult color. Eg. don’t publicly declare liver chestnut until you’re well beyond the foal shed, lest you look like a dingus.

The “color” gray

Since we’re already the topic of color, let’s go one step further, because gray is especially weird when it comes to foals. First you have to understand that gray isn’t actually a color, it’s a depigmentation. Therefore, no horse that ends up gray is actually born gray (this is also why gray horses continue to lose pigment and get whiter over time). The gray gene is a modifier that, when present, expresses on top of whatever color genes the horse already has. So a horse can be born literally any color, but if it has the gray gene it will eventually depigment and turn gray. The gray gene is also dominant, so if the horse has the gene, it WILL gray out. The gray gene cannot “hide” and then show up again further down the line in other generations. A gray horse will always have at least one gray parent. A horse with only one copy of the gray gene (heterozygous) has a 50% chance of passing it to an offspring. A horse with two copies of the gray gene (homozygous) has a 100% chance of passing it to the offspring. Another interesting note: foals that will eventually turn gray tend to be born hyperpigmented, or darker than foals that will not eventually turn gray. Eg. Ollie was a good example of all these things – he is grulla with a gray gene on top so will depigment over time from grulla to gray, and he was born hyperpigmented (which was the first clue that he got the gray gene).

I looooove color genetics, I could go on all day about that, but I’ll stop here. I wanted to hit the gray gene since we have a lot of foals coming next year by a gray stallion. Let’s get to the more complicated bits!

registries vs breeds

In the warmblood/sporthorse breeding world, there really isn’t such a thing as true breeds (except maybe Trakehner, and I’ll explain why in a second). If someone asks your favorite breed and you say Dutch Warmblood or Hanoverian or something like that, it sounds a little bit silly. Why? Because almost all of those European registries have “open” books – meaning they will allow stallions and mares for breeding within their own regstry that originated from another. This has become especially true within the last few decades with the prevalence and availability of shipped semen. Your Dutch Warmblood might actually come from Holsteiner, Selle Francais, and Hanoverian bloodlines. Your Oldenburg might have a lot of Hanoverian roots. Your Holsteiner might actually be largely thoroughbred (Mighty Magic is registered Holsteiner but is actually by a full TB stallion and out of a mare that also had a full TB sire). All of these different European-based registries, which are regional, end up intermingling, albeit some more than others. While technically still an open studbook, Holsteiner is typically less accepting of outside blood than a lot of other registries, for example.

All these different warmbloods aren’t breeds the way a Haflinger or a Friesian are – they are more of a TYPE (sporthorse, or warmblood) that contains different regional registries within said type. This is why, when it comes to sporthorses, it’s much more important to look at the actual names on the pedigree rather than the registry at the top of the page. The registry only tells you which studbook the horse is registered with, it doesn’t necessarily tell you anything about it’s actual lineage. The only major registry with a “closed” studbook is Trakehner, in that they have only allowed Trakehner, Arabian, and Thoroughbred horses to be used within their registry. E.g. Presto is registered Belgian Sporthorse (the studbook of the southern French-speaking region of Belgium, not to be confused with Belgian Warmblood which is the studbook of the northern Flemish region of Belgium) but he is by a stallion that himself was registered Holsteiner despite being mostly TB, and out of a mare who is registered RPSI but is actually by a Hanoverian stallion out of a TB mare. And of course, he’s never been to Belgium in his life, nor are either of his parents from Belgium. It’s a lot to unpack, but you can see why they aren’t really breeds.

approved vs registered

If that last one wasn’t enough to hurt your brain, I have one more super confusing but often misunderstood topic: the difference between approved vs registered. As I said above, these European-based warmblood registries tend to all intermingle. This is helped along largely by the fact that a single horse can be approved for breeding by multiple registries. In the world of sporthorses (with a few complicated exceptions), breeding stock must be inspected and approved in order to be used for breeding – you can’t just take one rando horse, breed it to another rando horse, and then get papers for it. The inspection and approval process provides a level of quality control, as every horse that is used for breeding within every registry has to meet a minimum standard of conformation, pedigree, and quality in order to be allowed to produce papered offspring. And while a horse can only have one set of papers – ie it can only be registered with one registry – it can be approved for breeding with as many as you like. This means a horse could produce offspring for any registry it meets approval for.

To use our same example, Mighty Magic (registered Holsteiner) is approved for breeding with: Selle Francais, Anglo-Arab, Holsteiner, Hanoverian, Oldenburg, Mecklenburg, Rhineland, Westfalian, Swedish Warmblood, and Zangersheide. Additionally, many registries (like Presto’s – Belgian Sporthorse) will also accept foals by known stallions with multiple approvals, even if they haven’t specifically obtained approval within their own. That means Mighty Magic can produce foals for any of those registries. He only has ONE set of registration papers, and he will never be anything but Holsteiner since that is his birth registry, but he can produce registered offspring for just about any other registry.

The same goes for mares. A mare can potentially be approved by as many registries as you want to take her to for inspection. It’s not uncommon at all for mares to have breeding approval from multiple registries. This is why she could also produce offspring for different registries. E.g. Sadie, for example, is registered RPSI but approved RPSI and Belgian Sporthorse, and has produced foals that have been registered both RPSI and Belgian Sporthorse (RPSI actually got absorbed into Westfalen a few years ago, to make it even MORE COMPLICATED but I won’t go down that rabbit trail). Theoretically, she could even produce full siblings that ended up registered differently. As with stallions, a mare will only ever have ONE registration, but she can have multiple breeding approvals and produce offspring for multiple registries. It’s important to note that registration also does not equal automatic approval – every horse of breeding age must be presented and pass inspection in order to be approved as breeding stock. Just because they are registered with said registry doesn’t mean they will be approved for breeding with said registry. Clear as mud?

Hopefully that helps a little bit… although maybe I just made it more confusing. It’s a super complicated world and we could go on about this forever, but I tried to just hit the main most important things. Is there anything I’ve mentioned before that I didn’t cover here? Or did all of this just stir up more questions (probably)? Drop it in the comments and I’ll address it!

17 thoughts on “Let’s talk Terminology

  1. The breed vs registry thing drives me NUTS!
    Coco was approved to be considered for Approval by the Holsteiner registry which I was pretty proud of (she’s registered RPSI). I never actually got her to an evaluation (yet), but it’s fun to know she could be considered.


  2. This was definitely helpful information! I’d love to hear your insights about different warmblood registries and their approval process, especially for TB mares. I’ve heard that some registries are a bit more accepting of TBs, while others are more harsh. Are there any that automatically approve Jockey Club registered TBs, or do they all have to be inspected?


    1. Yes, some are definitely more accepting of TB mares than others. While it’s possible to get some kind of registration (usually into a lower auxiliary book, or a “certificate of pedigree” as opposed to full papers) from some registries without having a mare inspected, I definitely wouldn’t recommend it. For TB mares especially IMO it’s super important to get feedback from the registry about her strengths and weaknesses with regard to a sporthorse type. Their word isn’t the be-all-end-all for sure, they can only grade what they see THAT DAY, but getting other eyes on your breeding stock is important, IMO.

      I personally don’t have an allegiance to any one registry, I tend to choose whichever one is most convenient for me and has the least red tape. Some of the TB friendlier ones, IMO, would be Westfalen, sBs (belgian sporthorse), and ISR/Oldenburg. Finding one with an inspection near you is usually what makes the decision.

      However, if you’re looking produce a stallion candidate, it’s best to choose a registry that has reciprocity with other registries so that he can be eligible for more approvals further down the line. The rules vary by registry as far as what other registries they will inspect stallion candidates from. It’s complicated LOL.


  3. The color genetics thing is one of my biggest pet peeve because honestly, how are there still functioning adults that don’t understand Punnett Squares? I finally had to delete an Andalusian breeder from my FB friends list because she insisted gray could skip generations and that breeding was basically “tossing every single ancestor’s color into a bag and pulling one out” and THAT’S NOT HOW IT WORKS DAMMIT. Cough. Anyway. I might have feelings about that. And I might also bookmark your post to send to idiots on the internet. Hahahaha.


    1. It’s just another warmblood registry, stands for Rheinland Pfalz-Saar International. Like I said, they don’t exist anymore, they got absorbed into Westfalen.


  4. Thank you for explaining this so succinctly. I want to print out the breed vs. registry part and shout it ver batim at a local “trainer” who “used to breed horses” but has NO idea how this works. She would go on and on about how she only likes Holsteiners and won’t look at an Oldenburg, so she therefore didn’t like the horse I was riding.. Well, the Oldenburg I was leasing was by Riverman, a registered Holsteiner. She refused to believe this was possible, what a moron.


  5. I also love color genetics, so I hear you there. I have a grey, and sometimes when she has “moments”, I remind her that she was born a BAY, not a chestnut! Haha.

    If anyone is interested a little more in how the approval process for a registry works, there was a really interesting article in the Arabian horse magazine about the process in a 2020 issue (found here, article starts on page 30: https://issuu.com/arabianhorseassociation/docs/arabian_horse_life_magazine__issue_2_2020). Obviously it talks about presenting your Arabian specifically, but even as a non-breeder (and my Arab definitely would’nt be approved, she’s too short!) I found it an informative read!


  6. Could you explain a little about branding? Is it hot vs cold? Is it just for young horses?Mandatory vs optional or differences in policy for different registries? What the rationale is since the brand usually is barely visible on an adult horse? Not looking to pass judgment here, just curious and something I’ve always been afraid to ask.


    1. Many of the registries have done away with branding now with the advent of the microchip. Some don’t brand any foals anymore at all, others make it optional. They all have microchips these days though. If they’re branded, it’s with a hot brand. A few people see it as a status symbol or a way to create a walking advertisement, but most people see it as yet another way to help easily identify a horse if it someday finds itself in a bad situation (indeed, I have seen the presence of a brand save many a kill pen horse by now).


  7. Thank you for this post. It makes things much clearer, especially the approved vs registered section.
    When does a registry typically brand? Is it done at an inspection/foal presentation? My lease mare is registered Hanoverian, but is unbranded. Born in 2007, I assuming that while she has been registered (DNA samples?) she quite possibly was never taken to an inspection?


    1. Only foals are branded, so if they aren’t branded at their foal inspection then the horse won’t be branded later. With your mare it’s possible that the owner opted to just not have her branded. That’s becoming more and more common.


  8. That explains so much that has confused me about European warmbloods over the years. Thank you!

    Personally, I like the European approach to registries much better than the American closed book breed system.


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