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The Road to a Foal: S's Breeding Saga Pt. 1


I chose Parcival for Sierra for many reasons.  Besides the fact that I have absolutely loved him for the majority of my horsey-life, he's getting up there in age (24 this year I believe) but more importantly, given that Sierra is unproven in the realm of motherhood and reproduction after having two foals by him out of a different mare, I have come to have an idea of what he passes onto his offspring and what he can offer a mare.  Both fillies had exceptional temperaments and willingness to learn, strong loin connections, well set necks and good bone.  The trot, and especially the canter, were also much improved in comparison to their mothers - all of which would benefit Sierra as well.  I have told myself that if I manage to get her in foal, I have to list it until weaning but I'm really hoping to keep the resulting foal for myself if it works out.

I began scanning Sierra a few months back, but V was my main focus.  It turns out, Vida has been a huge pain in my butt this year but I didn't want to miss Sierra, so I took some time to familiarize myself with her natural cycle - normal number of days in heat, how fast she grows a follicle, what type of edema she gets, and what size follicle she tends to ovulate on as well as how her Uterus looks during estrus.  Once I felt sufficiently comfortable and familiar with her cycle, I sped up her Ovulation with a drug called Deslorelin to see how long she takes to respond to it after learning that V takes her sweet time, resulting in dead semen by the time she ovulates (ask me how I learned this...).  Once she ovulated, I waited until a well suited time and short cycled her back with a different drug called Estrumate.

In the past, Sierra responded quickly to Estrumate, so I administered it on a Thursday evening, and she came back into heat in roughly 3 days.  Because of where I live, I can only order my Fresh Cooled Semen between Monday & Wednesday, otherwise it will sit somewhere over the weekend and be rotten cottage cheese upon arrival the following week.  Luckily for me, when I scanned Sierra on Tuesday afternoon I saw a healthy dominant follicle and some minor edema and contacted the stallion owner for my shipment.

They waited as late as possible to collect him given how long it takes to arrive to me, which worked fairly well.  The semen was scheduled to arrive on Friday afternoon, so I scanned her at noon to see how close she was to Ovulation.

I brought Sierra in, and immediately went to her left ovary, which housed the large dominant follicle I spotted a few days prior.. I was shocked to see it gone, and instead of growing it regressed.  She had no follicles of note on her left ovary anymore, with the largest being roughly 20mm in size. I was ready to throw myself on the floor in a temper tantrum, but remained hopeful that the other ovary looked more promising.  I had held off on scanning her on Wednesday or Thursday given that the semen was already on the road so I would only stress myself out more in doing so, and now I had been kicking myself.  I was fairly certain I had just wasted $300 on this shipment, but much to my surprise I found a large pre-ovulatory follicle on her right ovary.  I did a little happy dance and by the time I got everything cleaned up it was 1:00 PM.  I turned her back out and awaited the semens arrival, which was slotted for around 3:00 PM.  In the past, Sierra Ovulated within roughly 24 hours of Deslorelin and even if she responded quicker this time around, conception rates 6 hours post Ovulation are just as high as the 6 hours prior to Ov so I wasn't terribly worried.  I had to judge a horse show the following day which would render me away nearly all day so I was trying to avoid that being problematic, but the odds weren't in my favour.

6/12/21 at 12:00 (~41mm)

The semen arrived, and the breedable follicle I was following was starting to look even more ovulatory.  The walls were thickening, and the structure was losing shape while the uterine edema slowly reduced in grading - all great signs.  The shipment housed two full 60cc doses, and most maiden uterus' are incapable of holding much more than 40-60cc of fluid comfortably, which meant either wastage or room for more inseminations if I needed or wanted to.  Contrary to what most might think, less is more when it comes to putting fluid into a uterus and the uterus' natural inflammation response to semen can go into overdrive and make it more difficult to clear fluid if it's extra angry.

I decided to do my first insemination when the semen arrived given how fast the follicle had regressed in a matter of hours.  I brought Sierra in to get started.

First, I scanned her again to get a baseline of her Uterus and the follicle I was tracking.  I was surprised to see how much it had changed in just a matter of hours - the walls were thickening and losing definition in some areas, it had grown considerably, and was developing a pointed end.

6/12/21 4:00 PM (~40MM)

Next, I organized my things.

Once complete, I began my sanitizing to prep for the artificial insemination.  First, I braid her tail starting as high as possible. It doesn't have to be fancy by any means - she's not going into the show ring, it just makes it easier to wrap.

Next, I vet wrap it.  I tend to gravitate towards girly colours to channel those filly vibessssss.

I have a ring mounted to my stock for pulling tails to the side, and an adjustable bucket strap works flawlessly for the task.

Now, one of the most important parts - scrub, scrub, scrub and scrub some more then pat dry.  I like to use paper or shop towels.

Once that was complete, my hands were busy so I didn't get very many photos but firstly, I did a final visual check on Sierra's cervix with my .  I was looking for any abnormalities, but it looked like a perfect puddle on the vaginal floor.  Nerdily enough, horses, like most (or all) 'things', ,have a hymen.  When semen encounters blood it dies, so I had actually broken Sierra's a week or two prior and I wanted to ensure things were free and clear.  Luckily, things looked great, happy and receptive so I prepped my AI tools.

This pic is actually from after my last AI, but it shows how the syringes arrive. Originally, there was 2 60cc doses.

I removed the first syringe from the shipping container, which is literally just a cardboard box with a styrofoam box inside surrounded in ice packs - very high tech.  I attached the syringe to my pipette and pushed the semen to th eend of the pipette to avoid any air entering the uterus.  The hardest part, in my opinion, is getting safely through the cervix.  When in heat, the cervix literally turns into a soft, squishy puddle of tissue that falls onto the vaginal floor with a pea-sized hole you have to get through.  The tissue itself is sensitive and easily damaged, so special caution needs to be taken, but finding the hole and passing the pipette through it is a challenge in itself sometimes, but never the less I got through.  I deposited roughly 40cc of the dose into her uterus before I began to feel push back, telling me that was enough.

Whispering "Chromey Filly" as the first dose goes in!

Finally, the last step is to ultrasound again to confirm the semen was properly deposited into the uterus, and track the amount of fluid in the uterus over the hours (or days) that follow.  The cervix itself only stays open for about 3.5 days after ovulation, so the window of freeing the uterus of fluid is fairly wide, but still needs to be closely monitored.  Often the use of Oxytocin does the trick, but sometimes mares need veterinary attention that requires their uterus being filled with sterile fluid and/or medications, then drained and I try avoid that at all costs.

Oxytocin can be used for aborting unwanted pregnancies so special care needs to be taken when using it, but it only works on the uterine body and not on the oviducts or other areas of the reproductive track.  The 'baby' lives in the oviduct for roughly 5.5 days before descending into the uterus, plus with the cervix closing around 3.5 days, it's relatively safe to use in that time frame.  It is often administered 4-6 hours after breeding to help clear fluid, as that is typically how long it takes for the swimmers to reach their destination in the oviduct.  While I treated Sierra with Oxytocin throughout her cycle for safe measure, she did well clearing the fluid on her own.  

I scanned Sierra again 6 hours later to find minimal fluid, but unfortunately her follicle was still present and hadn't ovulated yet.  I had to make a decision and judging a horse show the following day threw a wrench in things, so I decided to get up at 4 AM and check her again.  The natural inflammation response of the uterus peaks around 12 hours post AI, but when I checked her I saw she hadn't ovulated yet but was very close and I made the decision to do another partial insemination.  I repeated the prepping process above, and sleepily went in again.  The semen itself looked pretty good still but I wouldn't call it great so I figured in this case, given that I had to leave for several hours and her uterus was clear from the insemination 12 hours earlier, another small deposit was reasonable.  I deposited another 30cc, and caught another hours sleep before I had to leave for the show.

This shows a small pocket of remaining fluid in the uterus 6 hours after the first AI

When I returned home from the show, I immediately put Sierra back in the stocks and found a freshly forming Corpus Luteum in place of the dominant follicle.  This meant that she had recently ovulated - based on the two scans, I suspected she had ovulated within 6-7 hours, so I decided to do one final insemination for good measure.  This time, I chose to do a Deep Horn Insemination, which requires a little more finessing as it involves inserting the pipette into the uterine horn, which connects to the oviduct.  By now, the semen was of significantly lower quality (entirely normal and acceptable given how long it had been), so I chose to do a DHI because it meant less swimming for the sperm to get to the egg.  DHI's are often done with frozen semen for that reason, and makes a person wish they had 3 more hands and bigger holes to work with as you need to guide the pipette rectally at the same time while trying to keep things clean, but never the less I got it done, depositing roughly 10cc into the horn, and the remainder in the uterine body as I exited for (hopefully) the last time.

A freshly forming Corpus Luteum ("CL"), which is the result of ovulation

Through it all, Sierra was a champ and was a perfect model for the processes.  I maintained scanning to keep an eye on the fluid, but she cleared it all with relative ease with the help of Oxytocin, and in the process an entire two days after the first Ovulation, she ovulated a second follicle on the opposite ovary.  I'm not terribly surprised because Deslorelin can cause that and I don't think the semen would have been viable at that point, but it's something worth noting nonetheless.

Regardless, Sierra's a little pissed off about being locked up in a paddock but she's been a perfect patient and now we anxiously await a preg check!


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