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HCG and fast ovulation

Equine-Reproduction.com Bulletin Board » Breeding Methods » HCG and fast ovulation « Previous Next »


Author Message
 

Allison Hagen
Neonate
Username: Boonies

Post Number: 2
Registered: 05-2005
Posted on Wednesday, July 27, 2005 - 11:50 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

2 mares bred using HCG.
The 1st mare ovulated within 20 hrs after giving her HCG at 40mm and she ovulated at 42mm. The 1st mare is not in foal and is now at day 14 showing a 48mm soft follicle on the rt side with the CL still evident on the left side.
Is this likely a mid cycle ovulation and would you consider breeding on it? Does it matter that I can see the CL from the last ovulation?

The 2nd mare I gave HCG at 44 MM and she ovulated at 48MM less than 24 hrs later. Anything I have read talks about the norm - and it seems to be longer than 24 hrs that they ovulate. Is there less likelihood of success when it goes this fast? My only other experience was 38 hrs post HCG.
 

Jos
Board Administrator
Username: Jos

Post Number: 10243
Registered: 10-1999
Posted on Wednesday, July 27, 2005 - 12:14 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

The average time to ovulation of 36-42 hours following hCG administration that is usually shown in literature is if the hCG is given in the presence of a 35mm follicle. If the follicle is larger, then the results will be more erratic, and a faster ovulation is likely, as you have found out.

If the first mare returned to estrus rapidly, I would be concerned about the possibility of a uterine infection. What you are seeing may be a follicle that will regress, but it might also be an ovulatory follicle as a result of an early return to estrus. In view of the fact that she was previously bred and is not pregnant, I would perform more diagnostics (a culture and cytology) prior to rebreeding if there is a suggestion that this may be an ovulatory follicle or early return to estrus was seen.

As you are giving hCG to follicles later than is normally recommended, as noted above you will not be likely to experience as controlled a response as most research literature gives. The follicle is already more developed, and consequently so is the oocyte, so a reduction in pregnancy rates as a result of a more rapid than desired ovulation is not likely.
 

Allison Hagen
Neonate
Username: Boonies

Post Number: 3
Registered: 05-2005
Posted on Thursday, July 28, 2005 - 04:08 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Thank you. That makes sense on the timing of the HCG. In u/s her - there is no evidence on the screen of infection. The body and horns look fairly homogenous with a slight texture that I usually see. Can there be an infection with out visible signs picked up on the u/s?
 

Jos
Board Administrator
Username: Jos

Post Number: 10244
Registered: 10-1999
Posted on Thursday, July 28, 2005 - 10:17 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Although one is more likely to see uterine fluid with specks in it if there is an infection present, there can sometimes be an infection present without evidence of fluid.

As a minimum, a cytology smear should assist diagnosis.
 

Allison Hagen
Neonate
Username: Boonies

Post Number: 4
Registered: 05-2005
Posted on Friday, August 05, 2005 - 02:44 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

This mare did not ovulate the midcycle follicle. It shrunk up to nothing. She did have a regular cycle right after that and exhibited good edema, teasing to the teaser stallion etc. I didn't use HCG on this one. Now, the issue is a double ovulation. She had a left ovulation which was bred with frozen very close to ovulation (within an hour post). She also had a follicle on the rt side that I didn't think was going to ovulate. I checked her 7 hrs after breeding the 1st ovulation and the other follicle on the rt was still there. Then checking her 12 hrs after that (19 hrs after breeding) the right follicle is gone(ovulating somewhere between 7 and 19 hrs after the first one). I am finding conflicting information on this. The frozen semen may or may not have lived long enough to fertilize the 2nd ovulation. If it did not live - and the 2nd ovulation goes unfertilized - assuming the 1st one was fertilized, does the 2nd ovulation kill the 1st fertilized ovulation?
I have read/heard that it is the 2nd ovulation that needs to be fertilized and not the 1st one.
Then I have heard that it doesn't matter and just worry about twins at this point. I am not clear on the timing of this and the effect of the 2nd ovulation on the 1st one.
Thanks
 

Jos
Board Administrator
Username: Jos

Post Number: 10254
Registered: 10-1999
Posted on Friday, August 05, 2005 - 09:02 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

does the 2nd ovulation kill the 1st fertilized ovulation?

No. That's how you get twins in the equine. Naturally occuring identical twins (from the splitting of an embryo) have only been identified a handful of times. Twins in the equine occur from double ovulations.

Check out the article about managing twin prenancies on this site for more information (follow that link).
 

Allison Hagen
Neonate
Username: Boonies

Post Number: 5
Registered: 05-2005
Posted on Friday, August 05, 2005 - 09:21 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Thank you. It is so late in the season, I would so much prefer the option of having to deal with twins than no pregnancy at all. I appreciate your response and your help via this board through this breeding season. This is the 1st year I have done this myself and it has definitely been a learning curve of the roller coaster type. I am looking forward to cleaning up the u/s machine and putting it away for the season!!
 

Chuck (Unregistered Guest)
Unregistered guest
Posted From: 66.81.174.135
Posted on Sunday, August 28, 2005 - 11:25 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

How does the 35mm follicle rule for HCG administration apply to draft mares? They won't typically ovulate until at a 50 or more. I use HCG but mostly as insurance that the mare will ovulate within the 36-48hrs and not hang on to the follicle. Experiences have produced varied results with no apparent trends.
 

Jos
Board Administrator
Username: Jos

Post Number: 10284
Registered: 10-1999
Posted on Monday, August 29, 2005 - 01:22 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Most other breeds such as warmbloods, throroughbreds and even some stock horses will regularly ovulate on follicles that are >50mm and respond to hCG in a predictable manner when given in the presence of a 35mm follicle. There are however mare exceptions. I would suggest therefore that you use as normal - on a 35mm follicle - and in the event that you do not see a predictable response wait until larger on the next cycle (perhaps 40mm), but be aware that this in itself may reduce reliability too. Again, this is likely to be mare dependent rather than specifically breed dependent.
 

harper quarter horses
Neonate
Username: Hqh

Post Number: 1
Registered: 04-2006
Posted on Tuesday, April 18, 2006 - 10:09 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

My mare's follicle measured 50 mm today at 4 pm CST, the cooled semen won't arrive until tomorrow afternoon. What are the chances of fertilization with these conditions? How large can follicles grow before ovulation?
 

carole whelan
Neonate
Username: Milmom

Post Number: 2
Registered: 05-2007
Posted on Tuesday, May 08, 2007 - 02:58 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

for Harper Q Horses- I believe this is dependent on individual mare, and even that can sometimes change. I'd always done well on observing cycles, always used one insemination to get a pregnancy. But, last year my mare, with always dependable cycles, was bred AI, 2 days later she had still not ovulated, follicle was 40mm and we inseminated again and gave her hcg. 2days later she had still not ovulated and had a 60mm follicle! What a mess, I thought, and my vet was leaving on a trip. I inseminated with a new shipment on her NINTH day of heat! and hoped for the best. And I got it- a pregnacy that resulted in the highest quality colt we have ever had. So strange things can happen. Did your mare ovulate before you got the semen?



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