This section takes into account that you have already had your mare examined by a vet, that they are visually reproductively sound and that all swabs and cultures have come back as perfectly normal or clear of issues. This is also for mares that present normal follicles in a regular pattern of 21 day cycles. I hope sharing this information helps at least one foal be born and saves 1000's in extra vet bills.
As mares get older, train a lot, have a lot of foals, they can develop a problem with their thyroid. We had a mare that didn’t conceive one year so we didn’t think much about it. She was 12 years old, had 7 foals previously, and was showing and training regularly. The second year we got pro-active and put her on Regumate (assists in keeping a mare pregnant). Even on Regumate she lost her foal between 30 and 45 days. We were shocked. How could a mare loose a foal on Regumate? Well a cheap test of her thyroid levels (Our vet charged $25) indicated that her thyroid was low. Conception and maintenance of pregnancy is very affected by the thyroid levels. If your having problems with conception this is worth a try. Some things to ask your equine nutritionist about if you find out that your horse has hypo-thyroid is Iodine and selenium in the diet plan.
Food for thought when breeding
Another thing that has recently been stirred up is how Soy is affecting breeding in horses. Soy contains phytoestrogens, which have estrogenic actions when added as a dietary supplement. There are no direct studies on horses but in humans, and rats ect. it's been found to affect the hormones and cause cycles to be irregular. There are a few horse breeders that have removed soy from their diets and found a significant increase in fertility and fetus retention. For stallions there would also be a concern about their semen potency. You can google how Estrogen affects your mare or stallion online. It's not necessarily a positive or negative but you should evaluate your needs. If your mare needs more Estrogen then soy may be a positive for her, if not then the excess could cause adverse reactions.
Another thing that I have experienced first hand with our Friesian mares it the use of ovulation inducing drugs interfering with conception and retention of embryos. There are far too many horses out there that are not Friesian and are successfully using these drugs for it to be something of notice BUT ... because I closely monitor all our mares by doing my own ultrasounding with increased frequency and monitor any and all medication that they receive I wanted to share something I noticed. I found that in many of my mares if I used any ovulation inducing drugs (combination or individual) that my conception % is greatly reduced and if conception does take place retention rate is lower and the embryo is usually lost between 28 and 55 days. Now those Friesian breeders out there are going to say... if you follow the directions and inject at 35mm (for 50 ovulation 36 hrs later) then you are doing it too soon for a Friesian. Yes, fully aware, so injection was between 45 and 48 (expected 55-65 ovulation in 36 hrs). Some didn't get past 50 for ovulation, some stayed past the 36 hrs and didn't actual ovulate (absorbed). I did have 1 mare successfully conceive, retain the foal while using ovulation inducing drugs and sadly lost her foal shortly after birth because of the aortic valve on the foal not closing after birth (see blog on aortic valve and Friesian). We can't connect the two incidents to each other. ** brand names are not shared because it is not the brand or product that is faulty in any way. Various brands were used over several years, the abnormalities are believed to be breed specific and are only mentioned to share trends that were experienced with Friesian mares. These situations were not witnessed with other breeds during this time
I would also like to include information about injectable hormones that cause the depletion of a Corpus Luteum (CL) to bring a mare back into cycle faster or short cycle them (prostaglandin). These hormones can also be used to terminate an unwanted pregnancy at the very early stages of pregnancy. With my Friesians I have notice that a mentionable few (not all) have not given me a viable follicle on the cycle post injection of these hormones. I have had a few conceptions using this hormone to "short cycle" a mare, however I should also mention I witnessed an elevation in early loss when these products were used (loss prior to 50 days).
** brand names are not shared because it is not the brand or product that is faulty in any way. Various brands were used over several years, the abnormalities are believed to be breed specific and are only mentioned to share trends that were experienced with Friesian mares. These situations were not witnessed with other breeds during this time.
The above two apply directly to my Embryo Transplant (ET) issues discussed below. The vet will most likely want to use an ovulation inducing drug to 1, better time the ovulation for accurate flushing at 7 days. 2, to save on semen shipments and make sure the semen gets there on time for the follicle and that the follicle lets go for the freshest semen. Ok those all sound good BUT if your mare fills the above description.... you won't have a viable follicle resulting in no conception or weak embryo at transplant and potentially early loss (before 50 days). You don't have to use this drug to do ET. You can ask the vet to scan the mare regularly till the mare naturally ovulates. You can ask the stallion owner to send 3 doses, or plan on a 2nd shipment if the stallion's semen doesn't last long. They can inseminate (Friesian at 50/55mm and 55/60mm and if they have to 60/65mm). Yes it's time consuming but if it's what it takes to get your foal it's not impossible.
Now the next step after flushing the embryo out is to give the mare the hormone to break down a CL so that if there is a 1% chance there is an embryo in there, it doesn't survive to conceive. Also so that the vet can get the mare back up and ready for another try because ET can take a few tries for complete success. BUT... again if your mare is like the one's above then the follicle the offer on 2nd cycle will be less viable and possibly contribute to not conceiving or early embryo loss for your try # 2 so you keep repeating again and again with the lower and lower success chances each cycle. You can do ET without this hormone. You can request that your vet not use it, and that they scan the mare at 15 days post ovulation and if the embryo is in there (usually not after the 3 flushes to transfer) but if it's there then you as the owner have 2 choices, keep a foal and have your mare carry, or pinch the embryo off and she will cycle again in about 5-7 days.
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