I am wandering the exact same thing! I just got back from having a 3 yr. old mare bred, and was wandering when to put her back in training? Worried to touch her right now, afraid of stopping implantation! I am DEFINATELY a trainer, and NOT a breeder. She is such a nice mare, and I DON'T want to make that trip to the stallion again is all I know!
The process of "implantation" is somewhat different in the equine, as you obviously are aware by your reference to the differentiation between fixation and implantation. FYI, fixation of the conceptus (when it ceases movement around the uterus) occurs about 16 days after fertilization.
It can be a little difficult to specifically define "implantation" in the equine though. In other species, implantation is typically considered to be occurring when the placenta starts to form and invade the lining of the uterus (the endometrium. Certainly we can use that time line as a definition for implantation with the equine, and if we do, the formation of the placenta starts around 40-45 days after fertilization. It is not finished in the equine until around 140 days of pregnancy.
The complication in the equine arises if we take the definition of "implantation" to mean the first invasion of the endometrium by a structure related to pregnancy, because around day 36 in the mare, some structures not specifically related to the placenta are formed that invade the endometrium. These are the endometrial cups, which through eCG (equine chorionic gonadotropin encourage formation of secondary CL's. One could therefore argue that implantation occurs in the mare around 36 days!
The safest thing to do is to either specify what definition one is using, or else give a general range - i.e. observe that implantation is initiated somewhere between 36 and 45 days in the equine.
Than in your opinion does a week of rest after breeding even make a difference in her keeping the pregnancy , or not? I was just wanting to put her back on her regular training schedule, wich is (not to vigorous, for my WP colts)light riding, several times daily. I have been told by the breeder, not to work her for a week until the egg implants in the uterus... Shows you what I know about equine reproduction. I'm glad I got on this website, I have heard clients talking about it for years!
Research done a few years ago at Texas A&M found that mares that continued work after breeding had about 50% the pregnancy rate when checked at 30 days compared to those checked at the same stage that ceased to work after being bred. The research was done in July and August at College Station, TX, and the conclusion drawn was that during those months, with a high ambient temperature, the mares that continued being worked increased their core temperatures to a point that caused embryonic death in a significant portion of them. In other words, if the weather is hot and the mare continues to be worked, there is a potential risk to pregnancy maintenance. It should be noted that the amount of work was not extreme - they were being walked, jogged and loped on an exerciser.
We know that overheating the conceptus under the microscope when performing embryo transfer has a negative effect on pregnancy maintenance, so it does seem not unreasonable that a similar effect would be seen in utero as well.
OH, I wish I hadn't of bred this amazing mare. Why didn't I talk to you first, and went with the regumate this show season? I am going to be SO paranoid to work her... at all! Thanks For the advice, & knowledge.
To the best of my knowledge, delayed implantation has not been identified in the equine.
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