Breeding myths...

[AndyPandy]

Older mares are more likely to have delayed uterine clearance issues. Embryos are flushed from the uterus. If these older mares were not given aggressive oxytocin therapy, then once the embryo dropped into the uterus, it will have been exposed to potentially unpleasant fluid in the uterus. This fluid is pretty likely to damage the embryo, as well as prevent fixation of the conceptus if it wasn't flushed.

In my opinion, it is probably the uterine-fluid-related-damage to the embryos from these older mares that caused the lower success rate. Unless the paper says that they did use oxytocin and that all the mares were cultured before they work was done.

[AJBliss]

Whoops! What you say makes sense. I think I misread my notes! Carnevale's subsequent study in 1995 after the one I mentioned (which was from 1993, not 1995!) actually collected oocytes from preovulatory follicles and transferred them into young, inseminated recipient mares. Guess I should re-read the whole thing. Thanks for letting me geek it up science-style and ask questions on this thread!

[alleycat]

I think you've persuaded me AP, with that last post; I think I'm wrong here...

Very patiently explained; and if you've thought that out yourself, I hope you've published it.

So, to change tack a bit, if a (human) female's oocytes don't all mature, does she jettison them at menopause, or are they still available but unused? If so is immaturity a problem? Could a post menopausal woman be an egg donor? (A friend of mine was lamenting the fact that she had never done this. Felt it was Flying in the Face of Nature at the time, but has modified her views; too late).

[AndyPandy]

I did think it out myself, but I'm sure other people have as well, so I won't be publishing it! Anyway, I'm more of an equine repro man than a human repro man. I'm really not sure if a post menopausal woman could be a donor. The problem is that primary oocytes must mature to become secondary oocytes before they have a follicle around then and can be ovulated. I guess, theoretically it would be possible to take an ovaian biopsy (OUCH!) and mature primary oocytes in vitro, however, I imagine that would be extremely time consuming, expensive and painful for the donor.

Also, I don't know if primary oocytes remain viable after the hormonal changes associated with menopause.

[alleycat]

Thanks yet again AP- excellent post!

[AndyPandy]

No worries. Thank you for adding to the discussion - I was just thinking how excellent this thread is, because people are actually discussing stuff in depth and bringing new ideas to the table Thanks for the nice comments too, very much appreciated.

[Bezique]

I have enjoyed this thread... I have found very informative! I love the bit about the 3000 balls, a great way to explain things!!

I have however been unable to contibrute to the thread on a sensible level because I am still finding myself highly amused that anyone would think...

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I drove my mare to the stud and knocked off the follicle!

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This comment has given me the giggles, everytime I have read it!!

**HG goes back to the naughty corner... until she can control herself**

[lisaward]

great thread very interesting

[DAHH]

[ QUOTE ]
.....he concluded that genetics may dictate adult height but a far greater influence was due to the available room for growth in the uterus and that this early disadvantage was not recovered in post parturition growth.

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From my own experience I would have to disagree. I think genetics play a much bigger role. I have a 15h2 mare who produces tiny foals. She looks huge when pregnant but gives then no room and evidently keeps all the goodness from feed for herself and passes very little to her foal (this is also highlighted by the fact that she still looks pregnant for months after the birth )
However her offspring always make up for the slow start. For example the 2 year old colt out of her (and by a 16h2 stallion) was tiny and very weak when born but he is now the biggest 2 year old I have, currently standing at 16h.
Of course I may change my mind in the future as last year I had a foal born to a 17 year old 16h2 mare (by a 17h2 stallion) whos uterus didn't expand enough. The result was a foal the same size as my springer spaniel, only with longer legs! He is still small for his age and I will let you know in a couple of years if I have changed my mind.....

[htobago]

Just wanted to say great thread, AP - I seem to learn something new and important every time you post on here!