Why - exactly - is it such a bad thing ... (older mare repro question)

[TrueColours]

to leave an older mare open for a breeding season? :confused:

I have read in many places that the absolute worst thing you can do with a late teens / early twenties mare is to leave her open for a season, as the NEXT season she will be very difficult or impossible to get in foal again and you may well then be stuck with a mare that can no longer conceive ever again ... whereas if you hadnt left her open that year, she could well conceive, carry and foal for sevearl more years ...

What - exactly - reproductively HAPPENS with an older mare to make this such a bad plan of action that wouldnt happen with a younger mare? And why would continuing to breed, be better than skipping a year with her?

[sfstable]

to leave an older mare open for a breeding season? :confused:

I have read in many places that the absolute worst thing you can do with a late teens / early twenties mare is to leave her open for a season, as the NEXT season she will be very difficult or impossible to get in foal again and you may well then be stuck with a mare that can no longer conceive ever again ... whereas if you hadnt left her open that year, she could well conceive, carry and foal for sevearl more years ...

What - exactly - reproductively HAPPENS with an older mare to make this such a bad plan of action that wouldnt happen with a younger mare? And why would continuing to breed, be better than skipping a year with her?

Good question, I would like to hear the answers myself. I have a 20 year old mare I would like to leave open this year. She still needs more "groceries" from her 2009 foaling experience and I would prefer she goes another year before I breed her again. But I don't want to compromise her ability to get into foal -- she is a great mother and produces very nice offspring.

[ne1]

cannot answer the question. have found the premise to be true though. i don't leave them open if i can help it, and when i've been forced to, more often than not its been really tough to catch them again.

[TrueColours]

I was hoping that Kathy would come on this thread and give us the exact reasons why leaving the older girls open isnt a good idea ...

Does anyone else know?

[Kinsella]

I do not know the actual reason, but have also experienced issues with getting an older mare in foal that was left open for a year. I do know that one of the reasons the Europeans generally breed their 3yo mares before competing them is so they do not have problems reproductively when the mares are older (after competing). Don't know the scientific reason behind that either, but it has been my experience that it is much harder to get an older (15+) maiden pregnant than one who had a foal years before...

[CowgirlDressage]

My husband & I took the breeding course at OSU, and Dr. Threfal said that once a mare is over a certain age, that leaving them open can allow more scarring of the tubes, etc., and thus decreases their chances of conceiving and carrying to term.

[TrueColours]

My husband & I took the breeding course at OSU, and Dr. Threfal said that once a mare is over a certain age, that leaving them open can allow more scarring of the tubes, etc., and thus decreases their chances of conceiving and carrying to term.


Do you remember what was said as to what happens to the tubes in an open mare that would cause them to get scarred?

And does this apply to older maiden mares equally as much as older mares that have been used as broodmares before?

[CowgirlDressage]

I don't recall the exact specifics, it was about 10 years ago, just that the aged mares thing stuck with me at the time.

I'm not sure I can locate my books & notes from then, but I will take a look and see.

I do remember something being said to the effect that aged maiden mares also begin developing some scar tissue simply from ovulating and aging, but again, it's been a while, and I don't have my books & notes.

Sorry not more specific, or helpful. I will take a look for them though.

[pintopiaffe]

I've had mares who took the choice out of my hands, and were every-other-year mares. I hemorhaged money the two years I tried to rebreed them with foal-at-side.

I'm also very interested in the science behind this, along with the multiparous vs. just aged mare question.

[naturalequus]

I am also very interested and eager to hear any science-backed replies!!!

My parents had a mare they bred a few times, with years in between, though in her younger years. We later leased her out and the lessee (who was actually the mare's previous owner - she really wanted a filly out of the mare, to carry on the lines), who tried breeding the mare through her late teens and into her twenties. She only caught and carried (when she was 19/20) once over a number of futile attempts. I can attest to a number of like situations, however I also do not know the reason behind it. Due to anectdotal evidence, I will be breeding the young mare I am likely to purchase, to make it easier for her to settle later in her teens after her career; it would be nice to understand the why's though!!

[Formosus]

I think the idea behind breeding a mare at least once when she is young has to do with the cervix. A mare that has carried a foal once tends not to have such a tight cervix. Older maiden mare have a tight cervix that often doesn't allow good uterus clearance post insemination.

As for why older multiparous mares are best kept in foal: I would love to understand why also...something to do with hormones cycles?

I'm sure Kathy will chime in at some point...

[TrueColours]

There are 2 mares a friend and I are looking at. One is 21 and the other is 23 or 24. Both have had foals, both have been open for several years and 2 years respectively

We both want to try with these girls - once - this year - but also recognize that if they dont catch, we now have the obligation of keeping them or finding them suitable retirement homes. Both have highly desirable bloodlines and would be well worth investing the time and money on

But we also both want to understand the "whys" of why older mares need to be kept in foal, in order to maximize the chances of getting them in foal in later years, before we make our decisions

Ive always heard that to be the case - that you never give an older mare a year off, but I have never heard any reasons given. Just "because" ... and everyone seems to believe the same thing to be true but cant explain "why" :)

Actually - I'll email a friend of mine as well, the link to this thread. Her husband is a very well known repro vet and I'd love to hear his take on it as well

[CrzyCorgi]

Very interesting discussion... Looking forward to some of the answers!

[ponygirl]

Someone else besides me want to tell my non maiden 11 yr old mare that she's supposed to be easy to breed? She's decided not listen to me at all about this.

[back in the saddle]

Is 14 considered old?

Mare in question had a foal last year but open now. She has had 6 foals total.

[TrueColours]

Had a friend of mine ask her repro vet yesterday "why" and he wasnt able to offer anything concrete either, just that the chances were not as good for getting them in foal (he "heard", and "his experience") if they were left open, but when pressed for an answer "why???" he could offer nothing in return ... :confused:

I am beginning to wonder if there is NO scientific validity to this at all, and if it does fall under the category of an "Old Wives Tale" and thats it. Along the lines of "If you Breed Two or Three Year Olds You Will Stunt Their Growth" :confused:

[mistyjewell]

While I have no "reason" or real experience (and I hope it's not true b/c I'm breeding my 17yo mare after she's had 2 years off) but I have known some breeders that always do every other year with their mares, saying it was better for them. So if that was the case then wouldn't they all not be able to be bred after a certian age? or less likely?

I've also known some horses that for whatever reason seem to be every other year mares, for several reasons, that unless they are heavily manipulated tend not to get in foal or stay in foal if they have a foal at their side.

So *shrugs* I remember from taking the equine reproduction class that mares don't have a decrease in egg fertility (ie still produce eggs that are "sound" eggs) and I'd imagine if you have a culture and cytology and biopsy done on these mares, and it all comes out good, there shouldn't, in theory, be a problem with them.

I wonder if part of the problem with older mares is that some of them may not have the back there conformation anymore, and maybe get dirty or have problems with clearence. If that's the case, and you're aware it may be a problem, we thankfully have enough techniques and tools these days to help with that.

TC, I'm guess these are TB mares? so this may not be an option, but if they have very valuable bloodlines and are older, maybe ET is a good option if the mares are difficult?

[TrueColours]

MJ - no - both mares I am referring to are WB mares

I wonder if part of the problem with older mares is that some of them may not have the back there conformation anymore, and maybe get dirty or have problems with clearence. If that's the case, and you're aware it may be a problem, we thankfully have enough techniques and tools these days to help with that.


But none of this makes any sense as to why an older mare that has been kept in foal right through her teens / early twenties is more apt to get in foal than one who has been left open for 1-2 years. The "back there" conformation should be the same on the mare regardless of whether she has been kept in foal or not and the being dirty or sucking wind I dont think would improve with being kept in foal constantly either???

I did PM Kathy and ask her to comment. I'll try again ... :)

[dmalbone]

In this instance, what would be considered old? It sounds subjective. It seems like there would need to be some scientific or physical validity and an age or physical condition to go along with it.

[pintopiaffe]

we know that uterine competency decreases with age... I wonder if it decreases with *number of cycles* ???

Now I'm just speculating, of course. ;) Passing the time 'till someone comes up with some science. :p

[ClassAction]

Speaking only as someone who studies reproduction in mice, our older females have ovaries that lack follicles supporting oocytes. And the oocytes that are there simply look like crap, they are atretic and the granulosa cells that support the oocyte are either undergoing apoptosis, changing their phenotype to something less desirable (neoplasia) or just not giving the oocyte the support it needs to mature and release from the ovary. If you'd like some pictures, PM me.

Also, yes, the estrus cycle hangs out either as persistent estrus or in the infertile diestrous phase.

As to the uterus itself, we haven't studied that in as much detail.

[TrueColours]

we know that uterine competency decreases with age... I wonder if it decreases with *number of cycles* ???

Now I'm just speculating, of course. Passing the time 'till someone comes up with some science.


Or - a "Use it or Lose It" type of situation??? ;)

In this instance, what would be considered old? It sounds subjective. It seems like there would need to be some scientific or physical validity and an age or physical condition to go along with it.

Not really I dont think ...

I believe that we are all of the belief (because we have "heard" this to be the case) that older mares that are NOT kept in foal are difficult to GET in foal. More difficult then older mares that have been kept in foal right through their teens and early twenties. I know that we all know that older mares have their own sets of issues but why are open ones supposedly harder to get pregnant than constantly pregnant ones are?? :confused:

Thats the question we are hanging out there and looking for an answer on and I believe it would apply to mares in their late teens into their early twenties ... :)

Speaking only as someone who studies reproduction in mice, our older females have ovaries that lack follicles supporting oocytes

Out of curiosity ... does this work the same for mice then? If you keep them constantly pregnant right through their reproductive lifetimes, is it easier to get them pregnant as they age, than an older mouse who you have given a few years off? Or has anyone studied such a thing in mice before?

[pintopiaffe]

um... isn't it more like *weeks* off with mice? Or *months* at the most?

:lol:

[ClassAction]

Out of curiosity ... does this work the same for mice then? If you keep them constantly pregnant right through their reproductive lifetimes, is it easier to get them pregnant as they age, than an older mouse who you have given a few years off? Or has anyone studied such a thing in mice before?

Well, our mice that we keep breeding tend to lose their fertility at about 1.5 years of age. Litter sizes decrease, longer time between pregnancies (mice have a gestation of 21 days and can and do get pregnant the day they give birth). Given that a mouse's life expectancy in our facility can be up to 2.5 years, that would translate beginning the decline in fertility in horses at about 18 in horse years (assuming a horse lives to 30, just to make the calculation easier).

At that age our mice tend to resorb their pregnancies as well. This means that they get pregnant and the pups implant in the uterine wall but for some reason the mom aborts the pregnancy by absorbing the pups back into her body.

[TrueColours]

um... isn't it more like *weeks* off with mice? Or *months* at the most?
:lol:


Yeah ... I think you have a pretty valid point there ... My "mouse repro knowledge" is sketchy at best!!! :lol:

ClassAction - so there doesnt appear to be any studies done and/or any correlation between mice left open opposed to those kept constantly pregnant and the ease with which they get pregnant (or not) compared to equines?

[ClassAction]

ClassAction - so there doesnt appear to be any studies done and/or any correlation between mice left open opposed to those kept constantly pregnant and the ease with which they get pregnant (or not) compared to equines?

Not to my knowledge. Let me do a pubmed search and get back to you.

[ClassAction]

Here is a paper on mechanisms in aging in the ovary: http://edrv.endojournals.org/cgi/content/full/30/5/465

Another article (in fact a few) link IGF-beta to ovarian health and oocyte viability. Although the methods used to get these levels are pretty invasive (have to get follicular fluid not blood).

[mistyjewell]

I'd be careful comparing mice to horses (or even human, reproducivley) Don't forget that they have multimple ovulations per cycle, cycle year round, and have different hormone "ques" as well as a totally different type of estrus then horses and humans have. Most mice that are used in reproductive studies usually have to be "humanized" in reference to the gene (genes) of interest. But if you look at the cycle and pregnancy of a mouse compared to horses it's like comparing apples to oranges, the might both bear fruit, but they are nothing a like, really.

PS, saw this on equine-repro's website, dont' know if it helps or not, but some good thoughts.

http://www.equine-reproduction.com/articles/MaidenMare.shtml

[mistyjewell]

Another thought. Most mares that are bred right after foaling still have some extra weight on them. I've seen, and had my vet comment, that if a mare is a little sunken in, sometimes extra weight can help without having to do a casslicks. In conjunction with that, mares having just foaled tend to not have infections, (unless there were birth complications etc) where mares with no foal at their side have a year to get them.

So maybe it's a question of breeders maintinance of mares inbetween foals then it is the mare itself. Or even that mares might get an infection somepoint after giving birth, and it's left there for 6 months +, and even if its caught maybe the damage has been done? Again, thinking that a good repro exam might be all that's needed to check for breeding soundess.

Or, another thought, is that maybe it's a prgesterone problem? That with the year (or more) off they just have problems with producing enough to maintain early pregnancies. Something regumate could help solve. Not sure why it might drop off if given a year off, but something that might be worth thinking about or looking into.

Again, I think it's one of those things if the mare is in good health and can handle the stress of a foal etc, I think its more of being on top of protential problems and checking everything out first. I think there may be a lot of breeders out there that don't want to spend the extra money on a lot of things, so they just don't get done and give the mare up as being "old" etc.

[ClassAction]

And here is a very nice paragraph from "Review of Ovarian Abnormalities in the Mare" by Patrick McCue:

"2. Age-Related Ovarian Dysfunction
Ovulatory dysfunction has been identified as a cause of subfertility in mares approximately 20 years of age or older. Older mares may have a longer inter- ovulatory interval than younger mares because of a longer follicular phase.16,17 A lengthening of the follicular phase in association with elevated gonado- tropin concentrations may indicate impending repro- ductive senescence in older mares.18 Complete ovulation failure or ovarian senescence has been observed in aged mares and may be due to an insufficient number of primordial follicles. In addi- tion, older mares may experience a delay in their initial ovulation of the year by an average of 2 weeks.
No effective treatments are currently available in the mare for promoting follicular growth in senes- cent ovaries. Predisposing factors for subfertility in older mares such as poor perineal conformation and ineffective uterine clearance should be addressed."

[TrueColours]

And here is a very nice paragraph from "Review of Ovarian Abnormalities in the Mare" by Patrick McCue:


And that again tells us that older mares are harder to get in foal than younger mares and why, but not why constantly in foal older mares are supposedly easier than open older ones ... ;)

[ClassAction]

I'd be careful comparing mice to horses (or even human, reproducivley) Don't forget that they have multimple ovulations per cycle, cycle year round, and have different hormone "ques" as well as a totally different type of estrus then horses and humans have. Most mice that are used in reproductive studies usually have to be "humanized" in reference to the gene (genes) of interest. But if you look at the cycle and pregnancy of a mouse compared to horses it's like comparing apples to oranges, the might both bear fruit, but they are nothing a like, really.


Well, yes it's not the same species but it is mighty easier to examine ovarian function at different time points in mice than in humans or even horses. :) Besides, we control for cycle, age, etc., as best we can. Our mice aren't knock-ins, they're wild-types and knock-outs.

And if you're looking to ask broad questions about fertility at a certain age, some things can be compared. I'm not asking to equate LH, FSH and E2 levels just a general trend of losing oocytes and follicles.

[ClassAction]

Well, the best way to understand why that might be happening is to understand the biology of aging in the reproductive system. I don't have any data on that specific question nor can I seem to find a study on it so I'm giving you the best data I CAN find.

Oh! for more research dollars!

[Equine Reproduction]

Causes for lowered fertility in older mares that are not bred every years are likely to be multi-factorial and possibly not all reasons are clearly defined.

A significant likelihood is that when a mare is "open" her cervix will be relaxed for about a week every three weeks when she comes into estrus, thereby allowing potential for pathogenic access to the uterus. If this is coupled with "relaxing" reproductive conformation ("tipping" of the uterus and poor vulval closure) as well as reduced immune response, there is an increased chance of endometritis. While this may be a very low grade endometritis, it still has the potential to reduce uterine condition (biopsy score) and therefore likelihood of pregnancy establishment. Similarly in the non-pregnant mare the uterus is open to insult all winter when the cervix relaxes during anestrus. This same period will not occur in the pregnant mare as of course her cervix is kept closed during pregnancy.

It has been hypothesized that oocyte numbers may be reduced in mares that are not bred by depletion of reserves as each non-bred/pregnant cycle may use multiple oocytes through development and regression. One has to consider however that the numbers involved are probably minimal compared to the overall numbers of oocytes present on an ovary at birth.

I might be worth considering also that the uterus that is pregnant has a continuous sustained blood flow to the endometrium during pregnancy in order to provide nutrients to the placenta (note that there is no blood transfer, merely nutrient transfer through the placenta). In the non-pregnant uterus, the blood flow may not be as sustained or present in the same manner.

As I note above, and am frequently heard to say, there is also a lot we do not yet understand about the equine uterus, and other factors therefore may be "part of the unknown"!

[EquusMagnificus]

Thanks Kathy :)

So basically, keeping the mares pregnant keeps the reproductive system well maintained and in good health. If not in use, time can wear and tear the tissues...

Plus really, mares are MADE to be pregnant at all times... Being "open" is a biological (human-made) error.

[TrueColours]

Plus really, mares are MADE to be pregnant at all times... Being "open" is a biological (human-made) error.


And thats why I have never understood breeders that voluntarily give their mares a year off, unless there is a strong physiological or reproductive reason for doing so

And I also hate it when the barbs are thrown at breeders that keep their girls in foal every year, as if they are abusing them in some way by doing so

Thanks Kathy - that does help put some of the pieces of the puzzle into place ... :)

[Hunters Peak]

I elusive older mare. The older mares are tricky and unpredictable. That being said, a few years ago we had an good older show mare. Produced some VERY good show horses later in life. Delivered a foal in July 2004 at 19. Mare had a grade C uterus at best at that point. We were always taught its not a good idea to leave a mare over 20 open if you hope to get more foals out of them. Owner decided to give the mare off due to the late foaling date. We were unable to get the mare in foal again. She would get pregnant hold for 25-30 days then lose the pregnancy. No amount of regumate or a caslick helped. We had a mare that was 17 and in foal for the first time, foaled every year through 22. Mares that continue to maintain pregnancy into their late teens to early twenties have continual blood flow and tone to the uterus, the cervix is closed for 11 months. Thus keeping the uterus and cervix in use. When its left open, the older mares, like older people lose muscle tone, condition, bloodflow, etc. Infection rates increase etc. Once that occurs its very hard to change that. It appears to be an effect of aging. I would suggest a biopsy, it will give you a place to start. What people need to understand is that pregnancy can be very taxing on the mare. People give them a year off to allow the uterus, uterine arteries, etc a chance to recover. Pregnancy and the weight of pregnancy over the years can put a tremdensous amount of strain on the uterus and the arteries. That can lead to tears, bleeds, and worse. I worry more about the older mares and foaling complications than getting them in foal, if they have had continual foals. Anyone who has ever seen a uterine bleed knows my fear of that. If I had a 15 year old mare, I'd give her a year off and have no worries about getting her back in foal. If I had a 20 year old mare, I would not give her a year off.

[pintopiaffe]

I had NO IDEA the cervix was relaxed during anestrous.

The simple things you'd think you'd know after doing this for 20+ years!!!

Thanks. I'm very glad someone actually ASKED this! :D

[TrueColours]

The repro vet that I alluded to in an earlier post was good enough to call me today and he has concurred with what Kathy and Jill (hunterspeak) have said as well - that if the mares stay open instead of being bred, on each cycle the cervix opens and as it opens, it allows contaminants in and once the contaminants get inside, they can and do play havoc and wreak some damage - some of it irreversible and some requiring a lot of micro management, time and money to get back under control again. So - the moral of the story is to not leave the older mares open at all!

We then touched on the subject of my Puchi Trap mare who has now had 6 foals in a row for me. I said I felt bad for her and as this was going to be #7 in a row, I was probably going to give her this year off as she was going to be 15 this year ...

He asked why? And was she in good shape or struggling? And I said I was thinking of doing so because I thought she needed a break and no - she looked fabulous, wasnt arthritic, wasnt dragged down by the foals at all, and I was very very conscientious as far as really upping her calories and food intake when she needed it and I was very happy with how she looked.

And his advice was that you stop regarding them in "human terms" and remember that they were designed to be in foal every year of their lives and as long as you looked after them properly, it was no harder on them to have a foal every single year, than it was to give them a year off in between and have them carry every second year instead

I guess when she IS struggling, and we need to jump through hoops to get her in foal or keep her in foal, and she isnt keeping her weight on well and she has rough foalings, then maybe that is the time to retire her and not when she appears to be having an easy time of it right from the beginning to the end, and back in foal once again ...

I have really appreciated all of the advice being given here. Now I understand the "whys" of not leaving older mares open - ever - and it makes complete and perfect sense ...

[SHWarmblood]

Maybe a tad off topic but to expand a little on mistyjewell's comment regarding the mare's preferential condition shortly after foaling, does anyone know why it is typically not recommended to breed mares on their foal heat? I have always elected to short-cycle my mares just after their foal heat, but I'm curious if there is another scientific reason why I've been warned not to breed mares on their foal heat.

[TrueColours]

I know when I collected my stallions at a well known and respected Standardbred facility many years ago, they had several hundred foals born there each year for their own and client mares and re-bred the mares there before sending them home.

The vet's first call every day was their farm, and EVERYTHING was checked over to the 9th degree and any issues that came up through foaling was noted and addressed and resolved immediately

They always bred on the foal heat as that was the name of the game in SB and TB racing - to get those foals on the ground as eraly as possible, so they really spared no expense and no attention to detail to get that accomplished each and every time and their success rate was sitting at 65-75% each year in doing so and those that didnt catch on the foal heat, caught the next go-round instead

I have always been told that if all inflammation has subsided, there are no post foaling infections present, the mare doesnt come into her foal heat too early (and you can manipulate that as well if your intention is to try and breed her on her foal heat) - then the success rate is very good for them getting in foal and keeping that pregnancy

I have personally never bred on a foal heat - I have always short cycled and bred again at Day 20-21, and have had great success with that method, but for the first time last year, everything fell into place with my Puchi Trap mare, the timing was good, I figured what the heck - I bred her and she did get in foal, so for the first time she is having a May foal instead of a June foal for me and that was exactly what I was hoping to accomplish with her ...