Comfort Without Compromise: Phenylbutazone and Mare Fertility

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Challenging conventional wisdom in equine reproduction, this episode explores revolutionary research about phenylbutazone's impact on embryo production in mares. When previous studies claimed mares on "bute" had zero successful embryos via intracytoplasmic sperm injection (ICSI), Dr. Kristen Loncar and her team questioned these findings based on their own clinical success. Their subsequent investigation reveals surprising results with significant implications for veterinary practice and equine welfare.

Dr. Loncar walks us through the evolution of transvaginal follicle aspiration and ICSI technology, which has transformed from a last-resort procedure for problem mares to an efficient breeding method for both aging broodmares and performance horses. She explains how their research tested various phenylbutazone formulations—liquid (oral and IV) and paste—finding no significant decrease in blastocyst rates compared to control groups. This groundbreaking discovery resolves a critical ethical dilemma: veterinarians no longer need to choose between managing a mare's pain and pursuing reproductive success.

The conversation delves into fascinating aspects of equine reproductive medicine, future research directions, and the potential role of AI in analyzing embryo development. Whether you're a practicing veterinarian, breeder, or horse owner, this episode provides essential insights into managing aging or arthritic mares while preserving their reproductive potential. Listen now to discover how science is enhancing both quality of life and reproductive options for horses under veterinary care.

JAVMA article: https://doi.org/10.2460/javma.25.04.0285

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Episode Transcript

Speaker 1 (00:00):
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Speaker 2 (00:35):
You're listening to Veterinary Vertex, a podcast of
the AVMA Journals.
In this episode we chat abouthow phenylbutazone treatment of
mares does not reduce embryoproduction via intracytoplasmic
sperm injection, with our guestKristen Lunker.

Speaker 3 (00:52):
Welcome listeners.
I'm Editor-in-Chief LisaFortier, and I'm joined by
Associate Editor Sarah Wright.
Today we have Kristen joiningus.
Kristen, thank you so much fortaking time out of this crazy
therogenology time frame in yourlife to be with us here today.
Thanks for having me.

Speaker 2 (01:08):
I'm really excited about this.
All right, let's trot on over.
So, kristen, your JABMA articlediscusses how mares that are
undergoing transvaginal follicleaspiration and intracytoplasmic
sperm injection can remain onphenylbutazone for comfort and
quality of life.
Please share with our listenersthe background on this article.
Yeah, so the whole process oftransvaginal aspiration and ICSI

(01:33):
has really evolved over thelast 20 plus years.
Initially it was kind of one ofthose last-ditch efforts for
those mares that are older andhad a lot of chronic uterine
problems where they couldn't bebred or have embryos fleshed
anymore.
And now there's been so manyadvances and it's actually

(01:53):
become a really efficient way ofmaking embryos.
So we do see a lot more young,healthy mares that can come in
so that way, if they're busytraining or showing, they can
just come in, get aspirated andpotentially make multiple
embryos from one session.
With that being said, we stillhave a very large population of

(02:17):
mares that are older.
A lot of them have chronicosteoarthritis issues.
I see a lot of laminitic maresthat come in anything like that
where they really need to be onsome sort of non-steroidal plus
or minus other medications to becomfortable, be able to

(02:38):
ambulate and just have arelatively decent quality of
life, just have a relativelydecent quality of life.
And so last year a paper cameout that described that mares
having 10 days of butte orphenylbutazone had a 0% blast
rate after ICSI.
And so at the clinic that Iwork at we read this paper and

(03:00):
we kind of went that doesn'treally fit with the clinical
picture that we see.
You know, we started going downthe list and naming all of the
mares that we could think of offthe top of our head of you know
.
Okay, this one's been on Butteand this one's been on Butte.
And so this project reallystarted, just kind of for our
own information we wanted toknow were our expectations

(03:27):
unrealistic?
You know, were we makingassumptions that were incorrect?
Is it really that detrimental?
And part of it was.
We wanted to know, since we hadsome embryos being produced,
okay, maybe there was a decreasethat we should be expecting and
we should kind of figure out.
Maybe there was a decrease thatwe should be expecting and we
should kind of figure out whatthat decrease was, so that when

(03:49):
we're talking with clients wecan come up with kind of all the
facts and have betterexpectations.
So it started off as just anin-house kind of wanting to know
situation and it definitelymorphed into multiple rounds,
multiple types of phenylbutazone.

(04:09):
And you know, the great thingwas that the mares that we were
using in our study we saw nodifferences and in fact some of
the mares that were onphenylbutazone had higher blast
rates than the control mares.
So at least we kind of got theinformation we were looking for
and have some information thatwe decided we wanted to share

(04:32):
with other veterinarians andother clients so that mares
would continue to remain onnon-steroidals if they needed
them and people wouldn't bescared off of it.
I feel like we hear that socommonly on this podcast like
hey, like we noticed this onething but thought differently.
So one to like actuallyinvestigate and see if there's
evidence to prove this.
So definitely a cool mythbuster, I think, for this

(04:54):
episode, which we appreciate.
And what are some of theimportant take-home messages
from this article?
The biggest take-home is thefact that it does seem to be
safe to leave these mares onphenylbutazone.
We didn't see any decrease inblastocyst rate.
We tested the liquidpreparation given orally, which

(05:16):
is fairly common in my area.
We tested the liquid given IVand we tested one of the paste
phenylbutazones in IV and wetested one of the paste
phenylbutazones, so there's anumber of options that we can
still use, and these mares stillproduced high numbers of
blastocysts.
So if you have a mare thatneeds to be on it, she certainly

(05:38):
doesn't need to come off justbecause you're trying to make
some embryos.

Speaker 3 (05:42):
Yeah, such great clinical, really important
clinical information.
So thank you for sharing that.
We have so many great optionsin veterinary medicine, so many
fabulous careers.
What sparked your interest intherogenology?

Speaker 2 (05:57):
That started all the way back in college.
I had an amazing professor thattaught reproductive physiology
and we had a breeding program atthe university, and so once you
took his class, you could thenparticipate in breeding and
foaling out the universityhorses, and so I just kind of

(06:22):
became fascinated at that point.
I was then given an opportunityto work at a really well-known
large Arabian breeding farmduring college and then after
that, during vet school, had anumber of mentors that kind of
showed me you know, you can'tactually make a career out of
this, which was amazing, andthings just kind of kept falling

(06:45):
into place.
So I ended up doing exactlywhat I was hoping I could do and
didn't think I could.

Speaker 3 (06:52):
A little bit earlier.
Sarah asked you and you nicelyarticulated what are some of the
important take-homes.
Mares can stay onphenylbutazone for their comfort
and no decrease in embryos.
But every time we do a studythere's something that surprises
us.
What do you think surprisedyour team about this study?
I think mostly.

Speaker 2 (07:09):
I was surprised at how little effect there was
Going into it.
We thought that there wasprobably going to be some
decrease.
There hasn't been a whole lotof work looking at what
different types of medicationsor supplements or anything like
that do to the oocyte, and so weknow when we give some sort of

(07:32):
non-steroidal, when we're tryingto breed a mare, we're going to
run into some problems.
We're going to have potentiallyincreased episodes of
hemorrhagic follicles, folliclesthat fail to ovulate.
We'll have increased fluidafter ovulating, but we really
didn't have any idea whathappens to the actual oocyte
itself, and so we assumed we'dhave some sort of a decrease.

(07:55):
We just didn't know what thatdecrease would be, and the fact
that there was no decrease atall was really surprising.
Yeah, super valuableinformation.
Thank you again for sharing itwith our journals.
So what are the next steps toresearch in this topic?
I think there's a couple thingsthat need to be done after this

(08:16):
.
Although not statisticallydifferent, we did see a lower
percentage of blasts producedwith the paste formulation, so I
don't know if that was just acoincidence or what.
We tried to use the same pastethat was used in the previous
study, where they had zero blastproduced but it wasn't

(08:40):
available.
So maybe there's something inthe paste, some sort of carrier,
that can actually causeproblems.
So it'd be really interestingto try a number of different
brands of the Butte paste to seeif that is potentially going to
be an issue.
And then after that, I mean weuse a number of different
non-steroidals in veterinarymedicine and it would be

(09:02):
interesting to see if any ofthem have effects, since we just
did phenylbutazone.
Always more questions thananswers sometimes.
So hopefully we'll see somemore work from you, kristen, and
do you see a role for AI inthis area of research?
I'm not really sure about theexact type of studies that we're
doing.

(09:23):
Just because there's so muchphysical work, it would be
really nice to have a way todesign the experiments.
You know we wanted to make surethat we had enough numbers that
our significance could beaccurate and trusted, so it
would be nice to have thestudies designed that way.

(09:43):
And then, obviously, the dataanalysis is always kind of the
hardest part, so that's alwaysnice.
I know not really related tothis study, but I know there's
AI being developed to analyzethe blastocysts as they're
developing, looking at cellularchanges and that sort of thing,
to kind of help predict theoutcome of each of these embryos

(10:06):
, because right now, you know,we kind of grade them based on
how well they develop, what theylook like at cleavage, how fast
they develop.
But I know there's AI beingdeveloped to really analyze, you
know, okay, this one has thischance versus this other one
that doesn't have as good of achance just based on what it

(10:27):
looked like at each little teeny, tiny change in the in the
process.
Very cool.
And for those of you justjoining us, we're discussing how
phenylbutazone treatment ofmares does not reduce embryo
production via intracytoplasmicsperm injection, with our guest
Kristen.

Speaker 3 (10:44):
Kristen, you talked about your wonderful exposure in
undergraduate and thenthroughout veterinary school, so
you have a lot of experience inthis field.
So how did all that combinedtraining help prepare you to
write this article and evenreally execute the study?

Speaker 2 (10:58):
So I think I have the training to do the procedures
that I've developed at thepractice that I'm currently at,
and then the training to kind ofdesign an appropriate study for
my residency.
So I've spent a lot of timeaspirating mares, getting more

(11:19):
efficient at that, doing theactual ICSI process in the lab,
and that's all just beenlearning on the job.
But the residency reallyprepared me to look at data
critically, design studies thathave appropriate controls.
We did crossovers to try tomake everything as even as

(11:40):
possible.
We tried to make it as blind aspossible so there wasn't any
sort of bias during theaspiration process or during the
injection process.
So there's been a lot of stepsalong the way where you learn
different techniques and pick updifferent methods of doing
things, and then, as well, thescientific part is just a whole

(12:02):
nother ballgame of difficulty.
And luckily I have a lot ofpeople in my life that were good
sounding boards and we couldbounce ideas off each other and
verify that we were doing thingskind of as thoroughly as we
could.
That's great.
Sounds like you had a reallygood team, so that's awesome to
hear.

(12:23):
Now, kristen, this next set ofquestions is going to be very
important for our listeners.
The first one is going to bedealing with the veterinarian's
perspective.
What is one piece ofinformation the veterinarian
should know about final venouszone treatment and embryo
production in mares?
The biggest thing as a managingvet is to continue to treat the
horse.
If you have a mare that needsto be on phenylbutazone, make

(12:47):
sure she stays on it andmaintains quality of life.
If I had the choice, I wouldprobably stick with either the
IV formulation given IV or givenorally versus the paste.
I just feel like we don't knowquite enough about the paste yet
, but since we didn't see astatistically significant

(13:08):
difference, if that's your onlyoption, I would absolutely not
stop it, just for the sake ofaspirating and creating embryos
and from the client'sperspective.
What's one thing clients shouldknow?
I think the clients need to becomfortable with the
veterinarian's decision to keepthe mare on butte as well.
We all know how fastinformation can travel, and so I

(13:33):
think that was one of thereasons this study went from
let's just see for our ownknowledge to we need to make
sure we do a thorough job andtry to get this published,
because we were concerned withthe previous article coming out
that the mares that were onphenylbutazone produced zero
embryos that clients would justlatch on to that.

(13:56):
You know one fact of not beingable to give my mare butte
anymore and and that's that.
And we absolutely don't wantmares to to be uncomfortable, we
don't want them to suffer, wedon't want any of that.
So we want to make sure thatclients understand that from a
scientific point of view, from aresearched point of view, they

(14:18):
can absolutely keep their mareon phenylbutazone and you're not
going to have an effect on theway she produces embryos.

Speaker 3 (14:28):
Yeah, you just have to keep reminding them.
There's a difference withembryos and other sorts of repro
and lots of I mean it's notuncommon to in my field of
regenerative medicine oh, theyhave to come off it before you
make PRP, and that's just nottrue platelet-rich plasma.
So yeah, we don't want them togo backwards in lameness or

(14:52):
discomfort for sure.
As we close, kristen, we liketo ask a little bit of a fun
fact and if you have it with you, you can show us, because this
is all video recordings you knowwhat's the oldest?
If you have it with you, youcan show us, because this is all
video recordings, you knowwhat's the oldest?
I'm a little afraid to ask atherogenologist this question,
like at all vet schools forlisteners, like when you go by
that, both the dental and thetherogenology, the old equipment
, you're like that's terrifying.
But Kristen, what's the oldestor most interesting item on your

(15:14):
desk or in your desk drawer?

Speaker 2 (15:16):
Oh, wow, I don't have it on me actually, which is sad
.
I have the Beatle heartbeatDoppler monitor that my dad
bought when my mom was pregnantwith me, which I think is super
cool.
I can't get it to work, but Ithink it's pretty cool just to

(15:37):
have because, you know, it's alittle bit of family history.
Very cool, and in your field,yeah, yeah, I love that.
Very cool, kristen.
Well, thank you so much forbeing here, kristen, and sharing
the manuscript with us as welland letting our listeners know
what they can expect when theyread your article.
Absolutely, this has been great.
Thank you so much.
And to our listeners, you canread Kristen's article on Jabma

(16:00):
I'm Sarah Wright with Lisa48.
Be on the lookout for nextweek's episode and don't forget
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