Researchers: Mare's Condition Appears to Impact Sex of Foal

[Fairview Horse Center]

http://www.thehorse.com/ViewArticle.aspx?ID=12917

For Nevada's breedings, the earlier born babies, are mostly colts. Mares tend to come out of the winter a bit thin and gain thru the spring/early summer. His later born foals have a much higher % of fillies. That would be a fat mare on a diet? Summer drought?

[Ritazza]

Makes sense to me! I guess when I breed my mare I'll have to put her on a diet.... no colts for me! :lol:

[dressagetraks]

So the reason my foundation broodmare is running 100% colts is that I (and her former owner, too) were too nice to her? Maybe we should change things for next spring. :lol:

[krfarms]

I always new my mares were different. Doobie's first foal was due after a long cold and snowy winter. She was a maiden, so I expected the foal sort of on time--well her "due" date came and went. She finally had the COLT at day 382!!!. The vets figured the foal sort of went "dormant" during the really cold weather. Then started growing again when the days lengthened in March and the days warmed up. The colt was born May 28th. Doobie lives to eat so she never got thin, and the colt was born healthy but not overly large considering he "cooked" longer!! lol

[DownYonder]

Maybe Mother Nature trying to look out for the species?

If mares are fat and sassy, the environment is conducive to expansion of the herd - i.e., it can support more females and their young.

If mares are lean, expansion of the herd may not be a good thing. More colts, less fillies mean less foals on the ground a few years down the road.

[goodmorning]

Well, maybe this will work out in my favor this year ;)

With my mares previous owner, her first year in foal she was a huge, fat, easy-keeper :yes: Delivered a large, healthy colt.

With her second foal, she was much harder to keep weight on, with no change in routine. Delivered a beautiful filly.

Once again she is not what I'd call an easy keeper - maybe I will have a beautiful filly....I wont hold my breath though ;)

[Manes and Tails]

DownYonder, you have it the wrong way around.

When times are good, females have more male babies. When times are hard, more females.

It's pretty simple, really.

Producing a foal takes a lot of energy. The species requires more females to produce the next generation than males. When that energy is limited, it's a better 'investment' to produce a female offspring, because you can manage with fewer males.

That makes at least two species that we have confirmed skew towards female offspring in 'hard times'. Guess what the other one is?

Humans.

They have, in fact, discovered that the primary reason for the developed world's skew towards female offspring is...women skipping breakfast. That alone is enough to trick the reproductive system into going 'Food's scarce!' and rejecting male fetuses.

I'd imagine that it's true in most mammals.

[Formosus]

The article, and other research on that very subject, make mention of the mare's condition prior to and up to conception. Once conception has occured: fat or thin will not change the sex of the foal I'm afraid!;)

[Sakura]

DownYonder, you have it the wrong way around.

When times are good, females have more male babies. When times are hard, more females.

It's pretty simple, really.

Producing a foal takes a lot of energy. The species requires more females to produce the next generation than males. When that energy is limited, it's a better 'investment' to produce a female offspring, because you can manage with fewer males.

That makes at least two species that we have confirmed skew towards female offspring in 'hard times'. Guess what the other one is?

Humans.

They have, in fact, discovered that the primary reason for the developed world's skew towards female offspring is...women skipping breakfast. That alone is enough to trick the reproductive system into going 'Food's scarce!' and rejecting male fetuses.

I'd imagine that it's true in most mammals.

Interesting... I was what would be considered underweight (5'6" 115) and skipped breakfast regularly (unless coffee is considered breakfast) when I found out that I was pregnant... had a boy.

My super easy keeper mare is in foal now... will be interesting to see if she foals a colt... I have a feeling it is a colt, but am keeping fingers crossed that it is indeed a filly.

[Sundown Farm]

I am really only hoping for 1 stallion prospect next year, of course, so I hope him to be a boy!! :D

Otherwise, I dont really care.. I love mares and stallions (not as much geldings), so we will see!! LOL

I have heard this before, and was hopeful that my hard keeper mare would produce a colt (since she was gaining weight)...

If this is all true, Elsie Rose (jc reg.) will have a colt sired by Rainbow next year!

[DressaginMadtown]

I heard over the weekend that the vets and researchers at Blue Mounds and Minitube a company in WI are working on a new technique that will allow vets to sex equine embryos prior to Embryo Transfer. How cool is that?

[Manes and Tails]

It's not an absolute thing, there are other factors. It's a -tendency-, not a certainty. Sex is also strongly influenced by uterine PH and by the sperm ratio production of the male (why some stallions seem to skew towards one sex or the other in their foals).