Question is I have a Maiden Friesian Mare (6yrs) this is the 4th time we are AI'ing her. None of the other ones worked. She tends to ovulate @46-50mm right now she is at a 40mm follicle is round, plan is to Ultrasound her tomorrow and depending on what it looks like I will go get semen on Thursday ( today is Tuesday) heres my question. Can we give her a Hcg shot on Thursday am and put semen in that evening or should the shot be given on Weds night? Would that be too long to wait? What is the time line on that shot? A Friesian breeder just told me he had a mare stay at 50mm for 3 days! If I give her the shot when she is at 40mm will it mature it or should I wait until the follicle changes shape?I dont want to loose anymore hair or money on this mare! GRRR
With regular mares, the majority of mares that receive hCG in the presence of a 35 mm follicle will ovulate in the region of 36-42 hours later (I think off the top of my head the statistic is 80%, but don't quote me!).
Note I said "regular"...
The rule of thumb with Friesian mares is to apply the rules for normal mares, then add 24 hours before you think of breeding... and then add another 24 hours before you actually do breed!!! For some reason Friesian mares seem to hang on to a follicle longer than "normal" mares before ovulating - either with or without hCG!
One thing that is important to understand is that hCG does not promote follicular growth, only follicular maturation. In other words, if one is dealing with a mare that predictably ovulates with a 45 mm follicle and has 3 mm of growth a day, and is given hCG on a 35 mm follicle, it does not mean that the follicle will grow more rapidly to 45 mm before ovulating, but will be most likely to ovulate at around a 40-42 size. In other words, if using hCG don't rely on follicular diameter as an indicator once given.
So do you think its even necessary to give an hCG shot at all with this big follicle? So with the shot it just ripens to a smaller size? It does not hasten it to get bigger to her normal 49mm faster? My breeder has a batch of mares coming in and said if we could up her to Thursday that would be better. Up her?! This AI game is driving me mad I swear. I know in her last time @ she had a standing heat for 3days then shut off just like that. They thought for sure she settled. If need be I can always make 2trips up to get semen they are only an hr1.5 away. They give me 2 doses and we put them in 24hrs apart. Maybe its my dumb luck for picking the hardest breed I could to get my feet wet at the AI biz. Thanks a bunch for all your advice...
It won't hurt to use the hCG (unless of course it caused her to ovulate before you got the semen, which is unlikely!), but it might help assure an ovulation in a more timely manner following insemination.
There really isn't a "correct" answer to this question, as the use of an ovulatory promoter is a matter of personal preference and the decision may vary with any given situation. I will say though that when using transported semen, the use of a promoter is more common than not.
You are correct in your summation that hCG does not promote follicular growth specifically, but rather maturation (there will of course be some growth, but not to the size normally seen at ovulation with any specific mare presuming timely use).
You might want to investigate the use of an oxytocin protocol if you are having difficulty settling this mare. It won't hurt, and may make all the difference.
Well I had her Ultrasound this am and her follicle grew a couple mm's.(42mm) And its still pretty round maybe a little more oblong not much tho. So we are going to US her again on Sat, ( in 3 days)to long of wait? Then possibly AI that evening. I did read your article on oxytocin, very good by the way. We did check for that last year and cultured her it was clean, and this year and he cant see any signs that would put her in that group. I would have to bring her to our area Repo clinic if we were going to try that. If she dosent settle this time. I hope Sat isent waiting to long, its so hard not to get jumpy when you know she is so big. Thanks for listening it somehow helps to talk about it.
Saturday might be pushing it... but she is a Friesian, so... ???
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