The Role of Genetics in Horse Temperament and Behavior

Join us to discuss the genetics behind temperament testing with Dr. Samantha Brooks, an esteemed associate professor at the University of Florida. This genetic discussion centers on the DRD4 gene region, a crucial piece in the complex picture of horse temperament. Dr. Brooks explains how DNA and life experiences combined can impact a horse's behavior. We begin our exploration with a study from Japan, offering insights that could dramatically impact horse management and selection practices across breeds.

The episode doesn't stop at theoretical knowledge; it continues into the practical arena of genetic testing and its role in the equine industry. Imagine selecting a horse with a temperament that complements your own, foreseeing its potential health trajectory, and gauging its suitability for various disciplines—all through the lens of genetics. Dr. Brooks shares riveting stories and real-world implications of these genetic profiles, demonstrating how they can influence a horse's behavior and performance. As we wrap up, anticipation builds for a second part to this episode where we focus on ancestry testing—a transformative tool that promises to shed light on personalized and informed horse ownership and training. Join us for this eye-opening conversation that will not only educate but also change the way we interact with and understand our hoofed partners.

Transcript

Lauren: 0:07

Welcome back to another episode of Genetics Unbridled. We have a very special episode today. Dr Samantha Brooks is joining us to talk about the genetics behind temperament testing on the DRD4 gene region. She's an associate professor of equine physiology and genetics at the University of Florida and is also one of our extremely valued scientific advisors. As an educator, dr Brooks is exceptional at breaking down very complex topics, so we felt that it would be best to discuss not one, but two hot topics with her In this part. One we'll focus on equine temperament testing. Is your horse curious, vigilant or both? We'll learn more about how these genetic results can impact you and your relationship with your horse. With that being said, krista, what are some things we should keep in mind when learning about this topic?

Christa: 0:55

No matter what you hear on this podcast, temperament is complicated and difficult to get to the bottom of, and that is why we're doing this podcast, because Dr Brooks and I and a number of people have been trying to sort out behavioral data such that we could prove or disprove genetic portions, pieces of temperament. It is really hard. So for the purposes of this podcast, the one test that we have evidence for at this point would be the DRD4 region, the one we offer for temperament. That's simply curiosity versus vigilance, but there's a whole bunch of other stuff going on. So with that introduction, dr Brooks, do you want to talk about what is known about that region, the DRD4, and how that test may or may not pertain to equine temperament?

Dr. Samantha Brooks: 1:53

Sure, sure.

Dr. Samantha Brooks: 1:54

So temperament is a fun target and in horses, as in most animals, we know that some of that temperament, particularly your innate reflexes, are strongly controlled by genetics. But a lot of it has to do with the environment and your lifelong history of learning and how that starts to adapt and change how you respond to different situations. It's a hard question, but for a horse geneticist it's probably the most tantalizing challenge to go after, because when you speak to horse owners it's one of the most valuable traits that they can name in their horse. So we all know the horse that maybe went lame, unfortunately, or wasn't entirely suitable for what you were asking them to do. But their personality is not a good term because they're not people per se, fortunately. But their attitude was so good and you enjoyed working with them so much that you kept them around far longer than you otherwise would have considered doing. And there's a lot of our horse activities where a willingness to try or a steady temperament or a little bit of extra enthusiasm for their job can carry a horse a long ways.

Christa: 3:37

A good horse analogy, a good horse personality.

Dr. Samantha Brooks: 3:44

Scientifically we say temperament, we don't tend to say personality. But for the average person, if you ask them to describe their horses tendencies, they'll say their personality. So just because it's hard doesn't mean we want to avoid trying to look at it scientifically, because there's so much opportunity there for gain to improve the way we select and manage our horses. So almost 20 years ago now, some of our scientific colleagues in Japan and Japan was a great place to do this research, in part because they have a very strong focus on horse welfare, especially on the racetrack. So they chose to start to investigate this idea that genetics could contribute towards temperament and they used a survey tool which is a little bit tough because it's not like a standardized scientific instrument. You're asking the grooms and the trainers and the exercise riders how they perceive this individual's horse personality rather than directly measuring it. But they got a very large sample of horses most of these active race horses on the track and asked a set of questions that were easily translatable to the folks that handle these horses every day, things like will he load easily on a trailer and is he willing to accept your normal everyday veterinary treatments like injections? These are very practical skills, like we've all known horses that didn't want to get on the trailer or that didn't like their annual vaccinations right.

Dr. Samantha Brooks: 5:26

What was really fascinating about this study is that when they looked specifically at a single gene because at that time they didn't have the funding and we didn't quite have the tools built out to consider the question from a genome-wide scale so they selected a single gene called DRD4.

Dr. Samantha Brooks: 5:45

That stands for dopamine receptor and it's the fourth one in that family of genes. That gene was interesting because in dogs and in humans there were already existing studies that identified correlations between different versions of this gene and different things, different types of behavioral traits. Like in dogs it was tied to aggression and in humans it's tied to things like thrill-seeking behavior, like your liability to go and jump out of planes for fun, or maybe among horse riders, your liability to be an eventer versus a strict dressage rider, and that gave them a good clue that this was a gene that made sense. It worked in other animals, so they thought it might play a role in horses. Interestingly enough, when they ran their statistics they could indeed see trends with different forms of the DRD4 gene and many of the aspects on their survey. Interestingly, the gene polymorphosome that they track comes in an A form and a G form. Krista correct me, is that right?

Christa: 6:58

Yep.

Dr. Samantha Brooks: 7:00

There's only, you know out, 2.7 billion bases. I don't remember if I remember at all right.

Christa: 7:05

It is. It is indeed, it's the GA Yep.

Dr. Samantha Brooks: 7:10

And when they looked across the trends in their survey, they identified that horses with one form tended to fall towards the curiosity scale of temperament traits and then the other end of the scale, they were what they called more vigilant. So these are the more standoffish, less investigative horses. I wouldn't go so far as to call them the spookier horses just yet, but there's definitely some interesting trends there. So this test is among thoroughbreds, has been investigated a couple of times and holds true quite well, although most horse owners have really never heard of it and we haven't yet had the opportunity to test it out in diverse breeds of horses to see how it may impact horse personality in all sorts of different types of horses.

Christa: 8:09

Oh, there's so much to say.

Lauren: 8:11

I know I'm like and I just am looking down at my outline that I have and the top four questions are answered.

Christa: 8:18

I told you she was good, I wasn't messing around, I tried to be efficient. No, that's great, super helpful. So there are things we're doing in the background and our clients know this people who've worked with us that we are investigating this. But, as we talked about right in the beginning, behavior is super hard to quantify and it's because it's subjective. And in the case of the Japanese investigators they are really. I mean, I don't know if I'm walking on the edge here of stereotyping, but when it comes to science, some of the Japanese investigators they are stone cold, awesome. They're just so rigid, so careful, so particular that their studies are so well controlled that they could pull this off.

Christa: 9:05

And now we're trying to do this by brute force, and by brute force I mean numbers. So we have to have many thousands more than the original study and we have to try and figure out a way to work with our crowdsourcing to quantify in human terms what they see their horse doing. But because it's subjective, if I ask somebody is your horse spooky? You might say, oh my god, yes, but in the next person's hand that's a lesson pony, it's fine. And so it's so subjective, right?

Christa: 9:41

And it's very hard to nail down what people are seeing versus what they are actually either manifesting in their horse or reporting, because they may not be the same. So behavior is also one of my favorite things, and I think this is where Sam and I get along like we just can't stand it. It's so much fun and so cool to watch and, in the course of genetics, now that things are expanding so quickly and the data is so readily available, I'm just going to venture out and say yes, when we offer this originally as a discovery thing, there's definitely pushback. Oh, there's no way you can determine a person, a horse analogy through a genotype, but I think there is or there is, at least in part.

Christa: 10:29

And I think there is evidence in the science that it's true for all mammals that there are definitely things that are genetically influenced and in some cases maybe even determined. But it's not everything. It's a part of it. But it could be a really big part of it and that's why we're doing what we're doing. We're kind of stepping outside of the lines and going OK, here's something really cool, we're going to give it to you. We're going to say look, it's discovery, what do you think? And fortunately, horse people some of them are probably pretty vigilant. They're thrill seekers, they're willing to kind of try this out and come back and say, ok, yeah, this holy cow, this really worked. And in other cases they're like what? Yeah? Fortunately it's more the former than the latter, but as things develop we'll offer more around behavior and then kind of wrap it all up in a neat package and see if it helps. We think it will.

Lauren: 11:24

Yeah, well, I know the Go ahead oh no, no, no.

Dr. Samantha Brooks: 11:28

I was going to say the applications are where things are really exciting and Mother Nature is really creative.

Christa: 11:34

Yes.

Dr. Samantha Brooks: 11:35

Even for our tests for things like coat colors, there is always an exception to the rule, because there's always a new combination or a new way those alleles come together.

Dr. Samantha Brooks: 11:45

Or five or five or ten. You know a genetic test of any kind is never going to make a decision for a horse owner or buyer or trainer completely cut and dry. It's always part of the equation and another tool to help them make better, educated decisions. So you know if you're going out to buy a horse, if I told you that a genetic test predicted even, say, 30% of that horse's likelihood to go lame from something like Navicular, you would love to have that information for the price point of an average genetic test, because you know you're already probably spending $1,000 on radiographs and your vet check and you've had your trainer come out, all of which is in the four figures easily.

Christa: 12:34

I was going to say $1,000. You have a coupon or something. I mean like, how are you doing that?

Dr. Samantha Brooks: 12:42

You know the dollar level, the average horse at the Brooks Farm, right, they're mostly cast off from other places. But you're investing big money already in the purchase and then potentially years of working to get this horse where you want it, in whatever discipline that is. So the idea that you could get a prediction of even 10, 20, 30% of that risk from a genetic test it's only a portion, but it's a sizeable chunk to help you make your decision right. So I use Lainness as an example, because that one's usually hot on the list of anyone doing a pre-purchase exam. But you know, if you have your, say, nine-year-old 4-H-er coming with you to look at a potential horse, wouldn't you like to know that?

Dr. Samantha Brooks: 13:33

The chances that they're going to be able to handle crowds and announcers and all the big noise once your kid takes this horse to state, or the chances that they will handle it better than others, especially if it's a horse that's untested? Or let's say you're a professional who is looking to take an off-the-track thoroughbred and turn it into a barrel eraser You're going to want those quick reflexes and that hot temperament right. So some of these genetic tools can help you to stack the deck a little in your favor, so that if you're choosing between two or three possible candidates or let's say you're a jumper barn with three young yearlings and you're trying to decide who to keep and who to sell you can stack the deck just a little bit to give you some extra information to help you make a more informed decision.

Christa: 14:24

Well, and if you win by half of a second, you still won Every little bit helps right Every little bit helps.

Lauren: 14:34

Yeah for sure. Well, I know one of the first podcasts I had listened to was Christa on Racers Edge and she was talking about curious and vigilant horses. And I know, from a listener perspective, I'm thinking, okay, this horse is this and this horse is that. And then I get my results back and it's very clear that I have a type for curious horses and so it's interesting to see when clients like have the same type of horse too and we talked about that in another recording. But it's really helpful, especially when you're just getting to know those animals and kind of understanding, okay, what's this relationship going to look like?

Christa: 15:08

Yep, how hard can I push? And if I don't get in with that horse on the first week, is it? Am I doomed or do I have a chance? Right, and in some cases you could be doomed.

Lauren: 15:22

Sam, I heard that you have horses too. I got to know. Do you have a preference to curious or vigilant type horses, or do you just like them all the same?

Dr. Samantha Brooks: 15:31

That's a good question. Well, I mean, I kind of like them all the same. To be honest, my young inventor has a copy of each, and his mom. Actually, she is definitely more on the vigilant side. I'm trying to remember what her genotype was, to be honest. But I know the young horse is genotype and he's definitely so. My young inventor is heterosegous and he's a very, very curious person and I'm going to jump in for it. And if you see him in the barn he's clearly the curious type Because he's the one who's grabbing the halters and shaking it around and don't leave the green box anywhere near him, because he's turned it over and he's investigating everything and very, very, very curious. But he can be quick and sometimes he's like, ok, we're going to jump this extra big just in case, because it looks like it might bite. And then we're going to do a research on the human personality questionnaires and pair that with their favorite horses horse personality genotypes and see if we can find the right mix between psychologies there.

Christa: 16:43

I do think that I think that will hold water, because just from doing client consult and working together with the horse people, we find that and this is just finger to the wind, finger to the data when an adult person buys horses, multiple horses, the ones that they mark as their favorites or the keepers they tend to be the same genotype and they don't even know they're doing it. That can't be random More work to be done.

Dr. Samantha Brooks: 17:09

More cool scientific studies.

Christa: 17:11

It never ends, like it never ends.

Lauren: 17:14

Thank you so much for listening to this episode of Genetics Unbridled. If you liked this episode, make sure to leave us a review and give us a follow. For more about Edelon and our latest information, make sure to follow us on Facebook and Instagram at EdelonDX, or visit our website, edelondxcom to learn more about our testing. Stay tuned for part two with Dr Brooks, where we discuss ancestry testing and what it will do for the equine industry. We'll see you next time.