I apologize in advance if there is already a thread here on this subject, but I couldn't find one.
In reading articles and forum threads about AI vs live cover, I have come across very heated debates about the quality of the resulting foal when using one method over the other.
The folks who hold steadfast to their belief that live cover is the only way, have an argument that I'd like to see explained in more scientific and quantitative terms.
These folks say that for AI, a stallion is collected and then the resulting collection is sometimes split several times and each portion goes to a different mare. Their argument is that there was originally one, or maybe a few, sperm which would have been the strongest/fastest/most enduring swimmers of the billions available. This particular sperm would have carried all the necessary genetic code to create the highest quality foal possible, given the relative qualities of both mare and stallion. If the collection is split several ways, what if that "super sperm" gets put into portion A, but your mare gets portion B? They say that your mare might get the best sperm out of portion B, but that would not be the best sperm from that stallion's collection. These people say the only way to guarantee the best possible quality and reproducibility of desirable traits is to use live cover, or to use AI, but inseminate using the entire collection. My thoughts were that each of the billions of sperm have the same odds of reaching their destination, and it's simply a crap shoot as to which one gets there first. Therefore, it wouldn't matter how many times the collection is split. However, we also know that full siblings are never 100% alike. Some are higher quality than others. What if there is some other force at play here, or some evolutionary reason that that one sperm is predestined to be the one? And by putting "him" in the "other" bag, we've just changed what Mother Nature intended to happen? This is what causes me to doubt my own thoughts, hence, the reason for posting these questions here.
Can anybody offer any knowledgeable insight into this, or point out any links showing case studies where this was explored? I'm just beginning my foray into breeding and I find this topic very interesting. Thanks, Den
There is no scientific basis, nor is there any scientific research that could support the theory.
The old theory was that by AI-ing, one gave (possibly the wrong) sperm a "head start" and that therefore the "best" sperm might not get there first. Then someone discovered that a stallion ejaculates directly into the uterus in a live cover situation, so that theory went out of the window.
There will continue to be theories put forward that cannot be proven one way or the other - primarily because they are impossible to create a "control" for in a research situation. Probably the best way to refute the argument is to look at performance though. Is performance in AI-sports still improving? The answer is "yes". Interestingly, one could also ask "are the speeds in Thoroughbred racing improving" to see if the hypothesis holds true that "the best" sperm are achieved with live cover... uh-oh... looks like there might be a little problem!
If I understand correctly, you mean that since the live cover ejaculate goes directly into the uterus, this creates even odds for each of the sperm, where each has a random chance at being the one? But once the ejaculate is in the uterus, don't the little "marathon runners" still need to enter and traverse part of the oviduct in order to reach the oocyte? This could present an evolutionary survival-of-the-fittest type of scenario, couldn't it? I don't mean to sound argumentative, just trying to understand more about the process. I wasn't aware that the AI-sports continue to improve, I'll have to look into that but, good point. Some of the anti-AI people continue to harp that the conformation and performance of AI-bred horses has declined dramatically over the years. But this may also have to do with the whole "halter horse" craze in certain breeds, where beauty is often bred for without regard to the usability of the horse! Very thought provoking! I wish there were studies to back up one theory or the other. Thanks for your thoughts, Den
You are correct in your understanding. The extrapolation however (from your perspective) relies on the concept that sperm transport is not random,and is solely mitigated by the sperm itself. Unfortunately, that too falls through the window, as it has been clearly demonstrated that the mare is a major driving force for sperm movement in the uterus - non-motile sperm have been retrieved from the oviductal region in slaughtered research situation, and they got there as a result of uterine contractions. Perhaps the "live cover afficiandos" will attempt to argue that the non-motile sperm are the "best" and therefore should be allowed to get there by the mare's uterine contractions, but I don't buy that argument! So - once again, the argument falls in the face of newer knowledge. First it was the argument that stallion supposedly ejaculating in the vagina vs. the insemination directly into uterus that failed; and now we have to consider that it's not all the sperm's doing that contributes to it's ability to get to the oviduct. Oh - and while we're on that subject, do we have to consider that PMN's, which are secreted by the mare and will attack and destroy sperm, only attack "bad" sperm, and not "good"...? Again, I think not!
Some of the anti-AI people continue to harp that the conformation and performance of AI-bred horses has declined dramatically over the years.
Have they looked at how the Thoroughbred has declined in conformational quality in the last 100 years? Can we say "feet" for example? Not in the case of many TB's we can't! But then, perhaps that doesn't come from the sperm!!! Bad selection tactics are the cause of declining qualities when seen, not bad sperm.
I thought I might add a little to your discussion. First of all I teach a reproduction course in both the equine and bovine. As far as AI vs Live coverage goes, the speed of the "fastest" sperm really doesn't matter all that much. The slowest sperm may actually be the one to get the job done. Realize that the sperm enters the uterus (AI or Live coverage) many hours before the egg is released. Once in the uterus, the sperm cells will randomly head in various directions. Some will travel into the right horn and some into the left horn. Others will actually travel out the cervix back into the vagina. If ovulation occurs on the right side ovary, then only those sperm that went in that direction have a chance. The sperm enter the oviduct and wait for the egg to be ovulated and travel down the oviduct. The sperm must wait there for at least 12 hours to undergo capacitation and gain the ability to fertilize the egg. It really doesn't matter how quick the sperm got there, they all have to wait for the egg. The main problem with using AI over live coverage is the fact that some people may be breeding studs that have no business reproducing. If a stallion has a conformation problem that prevents him from breeding naturally, then maybe he shouldn't be breeding by AI. Just my two cents worth!
I know the odds of A.I. being done post ovulation are slim but is there any research showing percentage of mares conceiving when insemenated is done 12 hrs after ovulation? My mare really surprised us this week by ovulating sooner than we expected. My vet feels there is still a high sucess rate of conception in this window but I failed to get excited knowing the articles I have read shows the odds are not in my favor. Any thoughts anyone?
Let me weigh in on another matter...that of saftey.
It seems to me that it is much safer to AI a horse then to do live cover. Safer for the handlers, safer for the animals. (Although there is some evidence that seems to suggest that some mares just cannot get pregnant without live cover or at the least extensive teasing.)
I for one appreciate having my mares at home, in a barn I know is clean (no transients and everyone is up to date in shots, woming, etc.) where they are comfortable. I also appreciate not having to trailer out, especially if the mare has a foal on her side. There are too many risks in trailering and with AI'ing, shipped semen makes more sense.
In this years breeding shed, we caught two mares on their foal heats..(can't remember what the "miss" statistic is for foal heat) and one took 3 tries...we missed her foal heat, missed the second heat and then changed studs and she caught. (Semen problem? Don't know.) We find out next week if we caught our final mare on HER foal heat. Catching 3 out of 4 mares on foal heat is pretty great odds!
Secret? Good mare management and good reproductive management I suppose...with a whole heaping of dumb luck and all the planets aligning thrown in. (Did I mention the pink shirts, the waving of keys over the mare after insemination and the chant..."the mare, she is pregnant"?)
Financially AI'ing beats live cover although not by much according to my research.
Hi Missy..anxious to hear what they say...my mare also, third attempt, we ordered semen for yesterday to AI, vet got here to put semen in and she'd already ovulated. We put it in anyway, hoping for the best! I know it has happened, so we are keeping our thoughts positive!
I am waiting to u/s Nicola....not really thinking she could be pregnant because the shipped semen only was at 5% when the vet inseminated and it turned out Nicola had an infection....Sounds like there is no chance....but stanger things have happened...maybe there is just one "Michael Phelps" in the 5% and I will be lucky LOL
But remember Terry, according to Dr. Dorn, the winner of THIS race does not have to be M. Phelps! It can be the slowest of the bunch! Keep hoping!!!!!
(I always thought it was the fastest swimmer too!)
Can you explain (Dr. Dorn) about the 12 hours? I am still a bit murky on that one! If I read what you are saying, even if the sperm arrive in the nick of time, if they have not been in the uterus for 12 hours, they cannot fertilize the egg? Or am I totally misundertanding?
I'm not Dr. Dorn, but I'm happy to explain capacitation for you. Or at least outline it...
A freshly ejaculated sperm is not capable of fertilizing an oocyte. It must undergo the capacitation process, which results in changes to a structure on the sperm called the acrosomal cap. The acrosomal cap is at the head end of the sperm, and perhaps one way to think of it is like a footballer's helmet - while intact (before capacitation) sperm will just "bounce off" anything they come into contact with (specifically an oocyte), but after the capacitatory changes occur, the football helmet is taken off, and the sperm can attach itself to the oocyte, and in essence "digest" it's way through the outer shell of the oocyte to achieve fertilization.
Capacitation can take place anywhere from 4 hours (a little sooner than the previously mentioned 12 hours) to up to 6 days after ejaculation, consequently the absolute earliest that an oocyte is likely to be fertilized is 4 hours after breeding. This is important if breeding post-ovulation only with fresh or cooled semen, as it means that one has to add that 4 hours to the time before fertilization takes place, and any breeding after 6 hours post ovulation will see a slight increase in EED. After 12 hours post-ovulation, there is a distinct increase in EED, and decrease in pregnancy rates overall.
With cooled semen, some of the sperm may actually undergo capacitation while in transit, and once capacitated, the duration of viability becomes reduced. that is one reason why sperm motility in such a situation is not necessarily related to fertility (i.e. you can have good motility and poor fertility).
Frozen semen presents another picture, as during the freezing/thawing process, changes to the acrosomal cap may occur, which are sometimes termed "cryo-capacitation". In other words, the sperm become sort of capacitated prior to insemination, and that means that they can achieve fertilization sooner than freshly ejaculated sperm. That is why we can breed up to 6 hours post-ovulation with frozen semen, and still see good pregnancy rates. It's also one reason why we may see good motility with frozen sperm, but poor fertility - if something goes wrong with the cryo-capacitation, and compromises the acrosomal cap.
This is extremely interesting. If my thinking is right, actually we are much better off breeding a little early than later. When I have mares here to breed live cover, I breed either on both day 3 & 5 or day 5 only. I've found it odd that upon U.S., the confirmed date of conception is often several days (up to 6, or once even more) after the last cover (live or A-I, doesn't seem to matter). That's always puzzled me, as the mare does go out of heat well before those 6 day readings.
From this information, I would surmise that inseminating at least a day before ovulation, or let's say when the follicle is in the low to mid 40's, might end up being better than hitting it very close to ovulation... right? This question relates more to those ordering semen than live cover. We'd be giving those little jocks more time to get undressed . Semen does seem to have a long life, at least that's been my experience with my own stallion.
There is no such thing as a "confirmed date of conception" unless the mare had been ultrasounded in such a manner as to indicate specific timing (i.e. u/s one day with a follicle present, and then the next she's ovulated with a CL present). All ultrasounds evaluating for pregnancy detection carry a "+/- x days" factor (e.g. 14 days +/- 4 days), so one cannot take a measurement of conceptus diameter as an indication of specific gestational duration (and hence the day of ovulation).
The fact that a mare is going out of heat is indicative that she has ovulated (in pretty much all cases). The lack of positive response and increase in negative response to the stallion's advances is caused by progesterone presence, and that progesterone comes from the CL, which is formed following ovulation. No progesterone = no negative response. That's why mares in winter anestrus if teased by a stallion usually have a "ho hum" attitude - no receptivity and no resistance.
Insemination with fresh or (reasonably fresh) cooled semen +/- 12-24 hours prior to ovulation is certainly acceptable and could be considered desirable timing with fertile semen. Remember that capacitation requires (typically) a minimum of 4 hours and the oocyte remains viable for a minimum of 6 hours (sometimes more) after ovulation, so even if the mare is bred at ovulation with fresh semen there still should be adequate time for fertilization before a decaying of the oocyte becomes a factor.
Duration of viability of sperm post-ejaculation is variable. Typically 48 hours is taken as the average, with up to 72 hours a not unreasonable expectation in many cases with on-farm use (AI or LC). It is however worth noting that if attempting to breed a long time before ovulation, one is also likely to see a lower pregnancy rate in the long run with a variety of stallions in the sample group, as some stallions will not have good longevity of sperm viability. It is therefore recommended that breeding on days 3, 5 and 7 of standing heat be maintained as a suitable timing program, as this will result in a superior pregnancy rate to reducing breedings through the mare's cycle unless ovulation is being pinpointed with the use of ultrasound or palpation.
You said: one cannot take a measurement of conceptus diameter as an indication of specific gestational duration (and hence the day of ovulation).
This clears it up for me! My veterinarian always tells me the "age" of the fetus... 21 day fetus, etc. so now I just know we are confirming a pregnancy, and not an exact date! THANK YOU. I learn something new every time I come here. You just can't have too much knowledge, or experience.
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