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Deslorelin question

Equine-Reproduction.com Bulletin Board » Breeding Methods » Deslorelin question « Previous Next »


Author Message
 

Julie G
Nursing Foal
Username: Julie_g

Post Number: 14
Registered: 07-2009
Posted on Thursday, August 13, 2009 - 07:56 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Hi - I have a question regarding Deslorelin use in breeds (warmbloods in particular) that produce LARGE follicles. My mare will often have a 35 mm or larger follicle on the first day of estrus. I usually wait until she is at Day 3 before giving Deslorelin when her follicle is generally over 40 mm. With Des, she will often ovulate a 45 mm follicle, but if left to ovulate naturally, she may go up to a 50 mm or larger before ovulating. I'm just wondering if a warmblood mare's ooycte is mature enough at 35 mm to give Des and if not, what markers should be used to gauge the optimum time to give Des? Any suggestions? Thanks.
 

Jos
Board Administrator
Username: Admin

Post Number: 2579
Registered: 10-1999
Posted on Thursday, August 13, 2009 - 08:17 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Deslorelin can be successfully given with the intent of stimulating ovulation to mares with 30 mm follicles or greater. Note that neither hCG nor Deslorelin significantly promote follicular growth, but rather the action of oocyte maturation and the ovulatory process, hence it is expectable that a mare that otherwise develops large follicles prior to ovulation would ovulate on a smaller follicle following treatment with either of those drugs.

The other marker (besides follicular diameter) that should be present when using either hCG or Deslorelin is uterine edema. If there has been no edema present on that estrus, results will be poor (to nil).
 

Julie G
Nursing Foal
Username: Julie_g

Post Number: 15
Registered: 07-2009
Posted on Thursday, August 13, 2009 - 09:11 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Great, thanks for the clarification.
 

Ann
Yearling
Username: Northernperch

Post Number: 90
Registered: 01-2008
Posted on Friday, August 14, 2009 - 07:40 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Also, don't forget that the follicle grows by about x3 every day so you can time it bit with the Des. So if you know she is a 35 on day 1, for example, by day 5 she would be approx at 50cm.
 

Jos
Board Administrator
Username: Admin

Post Number: 2581
Registered: 10-1999
Posted on Friday, August 14, 2009 - 10:11 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I'm not completely clear Ann on your meaning, but if you're saying what I think you are, then it's not quite correct.

A follicle not stimulated by hCG or Deslorelin will typically grow at the rate of 3 to 5 mm per day. Once an ovulation stimulator has been given however, that calculation is no longer valid or significant, as the size at which a follicle will ovulate will be smaller than if an ovulatory stimulation (OS) drug had not been given. In other words, one could say with a mare that had not been given an OS, that she commonly ovulates on an approximately 45 mm follicle, and she's at 30 mm today, so she will probably ovulate in 3-4 days, but if that mare is given Deslorelin, statistically about 80% will ovulate within 2 days, so the "growth factor" becomes insignificant as it doesn't occur.
 

Ann
Yearling
Username: Northernperch

Post Number: 91
Registered: 01-2008
Posted on Friday, August 14, 2009 - 12:04 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Jos, If I understood part of her question, it had to do with giving Des at the time when the follicle will be appropraitely sized. My point was that if the mare starts at 35cm and you want a follicle that is say 50cm, then you could WAIT to give the Des until the mare was approximately that size, taking in to consideration that a follicle will *typically* "grow" 3 cm a day. So if she is 35 cm day one, by day 5 she will be 50 cm, then give the Des to stimulate the relesse of the follicle. Of course Des works with 48 hours so you may cut lose a follicle that is 50cm or, f the Des takes the full 48 hours, the follicle may be approx 56 cm at the time it was released. At least that is our thought process (and our repro vet as well) and how we do things here on our farm with draft horses.

I hope that I am not misunderstanding you when you say that once the Des is given, follicle growth stops? That is not our understanding. (I am refering to the last sentence of your answer.)

Hope that clears up any confusion on what I was trying to say.
 

Jos
Board Administrator
Username: Admin

Post Number: 2582
Registered: 10-1999
Posted on Friday, August 14, 2009 - 12:31 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

There would be no real advantage to waiting until there was a large follicle (50 mm) before giving Deslorelin, and in fact one would lose a degree of predictability by doing so - when given on a 30-35 follicle, at least in light horses, ovulation may be anticipated to occur most commonly somewhere between 30-40 hours post-treatment. Giving it on a larger follicle could cause ovulation as soon as 12-24 hours, which of course if looking for a time to order semen (or collect and breed) could cause a problem!

Follicular growth does not stop once an ovulation promoter is given (hCG/Deslorelin), but one must not presume that growth will be at the same rate, nor that the mare's follicle will reach the size it normally does before ovulation without the use of a promoter. In other words, as I noted above, if one has a mare (to use your sizes) that commonly ovulates on a 56 mm follicle, and she is given Deslorelin or hCG when she has a 35 mm follicle, she is (statistically speaking) going to be likely to ovulate within 48 hours. If that follicle were to grow to it's "usual" 56 mm in that time frame, then one would be seeing a growth rate of about 10 mm/day - over double the "standard" 3-5 mm/day, and that increased growth rate doesn't happen. While the follicle will still continue to grow slightly, it would be more likely to see the ovulation occur with a follicle of ~45mm diameter. What I meant in my last sentence in the previous post was that one cannot therefore rely on follicular growth/diameter as an indication of impending ovulation after giving an OS (and in fact, it's not completely reliable even without the OS), but using time as the indicator is the significant factor (i.e. breed within 48 hours after giving the OS). To specifically address what I wrote (which as I see in re-reading it could be misinterpreted), "the 'growth factor' for timing to reach the anticipated normal pre-ovulatory diameter becomes insignificant as it (the anticipated normal pre-ovulatory diameter) doesn't occur" would have been better phraseology.
 

Ann
Yearling
Username: Northernperch

Post Number: 92
Registered: 01-2008
Posted on Friday, August 14, 2009 - 03:44 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Hi Jos, I guess things are just different in the heavey horse world. We U/S mares and note the follicle size. We then predict using the +/-3cm/rule a day in order to decide when to use Des. We like to see the follicle go to about 45-50 BEFORE using Des. We use the Des to time with getting chilled semen.

We would NEVER give Des to a mare with a follicle that was 35cm. We work closely with our vet, doing U/S everyday until follicle size is what we dem appropriate. Then we give the Des. We do try and predict ovulation using the 3cm a day rule and so far, we haven't missed a mare ovulating.

Wonderful thing about Fed Ex.....we order semen and ask that it be delievered next day before 10 a.m.. Giving the Des the night before we expect semen has never been an issue. Should the mare get the shot in the evening and she has blown the follicle that night (rarely happens) then we are still ok doing the insemination next day. If she hasn't ovulated, we put the semen in the next day anyway because with the Des, she will ovulate within 24-36 hours insemination.

This protocol works for us and this year, we had a 85% success rate getting mares pregnant on foal heats which is better then average.

Of course everyone's results may vary however, this way works for us.
 

Julie G
Nursing Foal
Username: Julie_g

Post Number: 16
Registered: 07-2009
Posted on Monday, August 17, 2009 - 10:48 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Correct me if I am wrong, Jos...

Deslorelin IS effective in inducing the ovulation of a mature oocyte when given on a 30-35 mm follicle even for breeds (warmblood in particular) that otherwise ovulate from large follicles (50 mm or greater). There shouldn't be any reason to wait until the mare reaches a 40 mm or larger, right?
 

Julie G
Nursing Foal
Username: Julie_g

Post Number: 17
Registered: 07-2009
Posted on Monday, August 17, 2009 - 10:56 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Oh, and I guess the really important factor Jos mentioned is that the mare should have significant uterine edema, right?? So, for example, a mare who on Day 1 of estrus has a 35 mm or larger follicle but does not have significant edema, one may need to wait a day or two until the edema really gets going before using Des.?? By then the follicle may be 40 mm or so... ??
 

Ann
Yearling
Username: Northernperch

Post Number: 93
Registered: 01-2008
Posted on Monday, August 17, 2009 - 02:09 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Julie, (and Jos) We have asked the question that you asked of our vet..if a bigger follicle means anything, if there is a reason to wait, etc and never really got a good answer. I suppose that if a follicle can become fertilized at 35 cm as easily as 50 cm, there would be no reason to wait. Unless there is some benfit to a larger follicle. I'll be interested to hear if anyone has any theories. (We just don't do Des at 35 cm because naturally, a draft horse won't ovulate at that size......and even tho' we are manipulating mother nature for our benefit we still try and stick kind of close to what she would do anyway, if that makes sense.)
 

Jos
Board Administrator
Username: Admin

Post Number: 2585
Registered: 10-1999
Posted on Monday, August 17, 2009 - 07:04 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Deslorelin IS effective in inducing the ovulation of a mature oocyte when given on a 30-35 mm follicle even for breeds (warmblood in particular) that otherwise ovulate from large follicles (50 mm or greater). There shouldn't be any reason to wait until the mare reaches a 40 mm or larger, right?

It has been my experience, and the experience of other researchers, that giving Deslorelin to a mare with a 30-35 mm follicle promotes ovulation within 48 hours. We (and others) have found this to be the case in warmblood horses (of which we see a fair number each year) and even draught horses (of which we see a lesser number). I therefore would see no particular benefit to waiting until there was a larger follicle present, especially because - as I noted above - the reliability of the timing of the subsequent ovulation becomes less predictable, making it harder to time insemination correctly if dealing with transported semen.

The size follicle that a mare normally develops prior to ovulation has little to do with the efficacy of, or when to use Deslorelin (or hCG). Although as I noted we see fewer draught mares each year than warmbloods, some warmblood mares will routinely develop 50+ mm follicles prior to ovulation if left to their own devices, but we will still give them an OS agent at 30-35 mm with edema present and expect results within 48 hours.
 

Julie G
Weanling
Username: Julie_g

Post Number: 22
Registered: 07-2009
Posted on Monday, August 17, 2009 - 07:13 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Excellent...that is very clear, thank you!



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