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HorseAdvice.com » Treatments and Medications for Horses » Reproductive Drugs » Human Chorionic Gonadotropin (HCG) »
  Discussion on Timing of the hcg injection
Author Message
New Member:
Janeh

Posted on Thursday, Jun 17, 2004 - 8:12 am:

I am new to the breeding world. We bred my mare on her last cycle using AI. An injection of HCG was given, along with the second dose of semen. The egg was 50mm and very soft. We performed an ultrasound on day 18 and discovered that, not only was she not pregnant, but she already had a 42mm egg on one of her ovaries. We are going to try again, but I want to be sure that I do everything that I am able to do, in order to increase our chances of pregnancy.

Here are my questions: 1) If her egg went to 50mm on her last heat, will it go to at least 50mm every heat? 2)Should we inject her with HCG with the first insemenination? 3) How long does it take for the injection of HCG to cause ovulation? 4) Does HCG always cause ovulation?

It seems to me that if we inject her with HCG with the first insemenination, then we can ultrasound her the next day, prior to the second insemenination and see if she has ovulated.

I appreciate any advice

Jane
Member:
Eoeo

Posted on Thursday, Jun 17, 2004 - 9:29 am:

Jane, we used HCG several times this year. We also had weather that was warm then went cold and back to warm and then cold several times while breeding. The HCG didn't seem to take them out of heat any faster than 48 hours. We weren't ultrasounding so I assume they ovulated within 24 hours of the breeding and the shot. The heats we didn't use HCG lasted 6 to 7 days. With a 50mm follicle that was soft, I would assume it was ready to pop and should have been caught. However, for whatever reasons, these mares don't always cooperate. If you had another 50mm, I would inseminate, give the shot and then be prepared to inseminate a 2nd time if need be. As I understand, even if she ovulates, if she is inseminated within 6 hours of ovulation, she could still catch. Dr. O, please advise if this is true. Good Luck. BTW, we had our first mare ultrasounded with a 55mm follicle. She stayed in heat and bred for 3 more days, we didn't give her a shot to go out as it was early in the season. EO
Moderator:
DrO

Posted on Saturday, Jun 19, 2004 - 9:20 am:

Hello Jane,
1) Not neccesarily, but I find mares that ovulate big follicles tend to do so repeatedly.
2,3,4) Not all of your following questions have straight forward answers and the issues are addressed in the article associated with this forum Jane, see the paragrahps subtitled HCG.

LKR, yes up to 6 hours post ovulation seems to be allowable for a acceptable conception rate though some work suggests conception rates start declining at 2 hours post ovulation. Also some studies have found a higher rate of early embryonic loss in this group, see Equine Reproduction » Breeding and Foaling » Breeding Patterns in Mares and Stallions for more.
DrO
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