[VirginiaBred]

Who believes this?

Frail Broodmare? Expect a Filly

Cold and wet weather combined with a rather hard-keeping breed of horses means that Thoroughbred caregivers must be especially conscientious about the health of their equine charges during the winter months.
In other words, winter is a rough time of year to be a Thoroughbred owner.
It becomes an even more crucial -- and difficult -- responsibility for Thoroughbred breeders, who must keep broodmares in top condition throughout the lean months. I know from experience that some mares are just harder to manage than others -- blanketing, multiple grain rations, and high-quality hay are just the bare requirements for some mares when they're in foal or preparing to be bred.
A few months back, I read a fascinating story on TheHorse.com (Researchers: Mare's Condition Appears to Impact Sex of Foal) that associates the relative condition of the mare (at the time of breeding) with the eventual sex of her foal. With Thoroughbred breeding season ramping up in just a few weeks, I thought it was a good time to share the article. In a nutshell, the author reports research that shows an overwhelming percentage of mares that were gaining condition at the time of conception produced colts, while mares that were losing condition at the time of breeding tended to produce fillies. (Read the article for some additional analysis.)
The best practice -- and one that results in an equitable distribution of colts and fillies -- is for broodmares to maintain condition throughout the year.
That's a tall order when you have a hard keeper. During the winter, I feed one of my mares a spectacular quantity of feed to make sure she keeps good form. High-protein sweet feed is augmented with mashes containing beet pulp and flax,-- fed twice daily. High-quality hay is free-fed, and supplemented with soaked alfalfa cubes. That plus blanketing in sub-30 degree temperatures does the trick for this particular mare, but I know there are much more difficult cases out there. (Another of my mares could get fat on a single flake of grass hay each day. Go figure!)


www.bloodhorse.com

[Kennysadsack]

This is a new one. Not sure I buy it.

[JB]

Interesting.

It's known that pH balances play a role in whether or not the male or female swimmers are more likely to die off sooner. The article mentions something about glucose level manipulation causing a shift in the sex ratio of mice, so perhaps the glucose issue affects pH or another factor that kills one sex sperm or the other, or slows one down, or something of that nature.

[Laurierace]

This isn't a new theory. I even remember it being discussed here before. My mare is usually neither gaining condition nor losing condition when being mated so I guess that puts us back to a 50/50 chance.

[VirginiaBred]

Agree Laurie.

[Home Again Farm]

I have two mares that generally hold their condition, so do not tend to be gaining or losing at conception. One is 7 out of 8 for fillies and the other is 5 out of 6 for fillies. I don't put a lot of faith into that research. My own experience has shown that when a mare is bred far in front of ovulaton, we get a filly. Otherwise, I see no pattern using fresh or frozen semen.

[VirginiaBred]

What was the verdict on how a mare carries - whether it's a colt or a filly, or is that also an unproven?

[ShannonD]

Interesting.

It's known that pH balances play a role in whether or not the male or female swimmers are more likely to die off sooner. The article mentions something about glucose level manipulation causing a shift in the sex ratio of mice, so perhaps the glucose issue affects pH or another factor that kills one sex sperm or the other, or slows one down, or something of that nature.

J, do you know if it said higher glucose = male or filly?

I am secretly testing this theory this year. My mare lost quite a bit of weight over the winter while in a lease situation and we are working to put weight back on her. She will be bred this heat or next. I'm interested to see if it will be colt or filly.

Weren't the numbers something like 97% of the time a mare gaining condition will have a colt? I don't know if it specified in the link in the OP, but that's what I seem to remember.

ETA-- oops, but now I see where I got the 97% from...

In mares that were gaining weight at the time of conception, 80% had a colt, while only 3% who were losing weight gave birth to a colt.

[JoZ]

I don't know if this is reasonable for domesticated horses. I am sure that for the most part, we are not seeing the extremes that a horse on the range may encounter in terms of scarce vs. plentiful resources.

I bred my favorite mare every other year (foals in 2005, 2007, 2009) but bred her again last year for a 2010 foal. She is an easy keeper but maybe, just maybe, her system might have registered as "losing condition" last year with a foal at side. I am clinging to this because I really want a filly after three colts!!!

[JB]

J, do you know if it said higher glucose = male or filly?

Nope, the article only said it changed the sex ratio

I am secretly testing this theory this year. My mare lost quite a bit of weight over the winter while in a lease situation and we are working to put weight back on her. She will be bred this heat or next. I'm interested to see if it will be colt or filly.

LOL, I kept my mare in the best weight ever this Winter so does that mean I should get whatever you don't?

[RyTimMick]

PH can have a dramatic effect on sex. Under wasting conditions muscle is being consumed which can lead to ketosis. This is an acidic condition. So the lower PH could have an effect. If this is true, then the Lower PH would select for female swimmers.

Tim

[VirginiaBred]

I wonder if a lower acidic condition leads to any kind of problems later, i.e. contractions, etc.

[Brutust]

I do not know if this theory is believable or not but my mare has had four foals: 2 colts and 2 fillies. I noted that when her fillies were conceived, the mare had lost condition prior to being inseminated.

[gypsymare]

Sort of unrelated but I remember reading somewhere that older stallions sired a higher percentage of colts. Something about nature selecting for a replacement for the aging herd stallion.

[Beentheredonethat]

Well, I think it's fun, but not true. My vet was betting my last foal would be a colt because we inseminated almost right on ovulation, and she says male sperm are faster swimmers. She has a theory that insemination closer to ovulation produces colts, further away produces fillies.

We were right on insemination--got a filly!

Oh, and the mare was new, completely out of shape. Bred her within six months of getting her and she was going from being completely out of condition to muscling up and working 1st level. So that shoots the theory. She was gaining muscle, fitness and weight while inseminated and preggers.

Now she's in REALLY good shape, working on tempi changes, piaffe, and passage and is carrying MUCH more weight than she did the last time. We'll see what you get. For some reason I'm thinking a colt.

[Dressage_Diva333]

My findings for the 2008 foaling season (2009 foaling season) were as follows, all bred with fresh semen, if that matters:

Mare was underweight, and gaining condition = Filly

I cut this mare's feed, as she was quite fat during breed = Filly

Also cut this mare's feed, she has always been 'plump' = Colt

Mare was gaining weight, but also being put into work = Colt

Mare was VERY fat, and stayed consistent = Filly



So I don't really see a pattern, I tend to keep my horses on the plump side in general... The first three last year were by the same stallion, second two were different stallions. I did note that one of my mares was gaining condition when bred this year, and two were losing slightly, we will find out in May and June what the results will be

[railmom]

I have a mare who is a very easy keeper Bel Etrice has had seven foals in a row. Colt, filly, colt, filly, colt, filly, colt. Last year she had off. I am guessing since she had a year off, I missed my filly and this will be a colt year. My vet is betting I will get my filly anyway and not ruin the pattern... the things we do to entertain while waiting for foals, LOL!

The old, young stallion, fresh, frozen thing doesn't work here. She has had both fillies and colts from older (Donnerschlag, Pablo) and younger stallions (Rascalino, Quaterback) as well as both from fresh (3 colts, 2fillies) and frozen (one colt, one filly). So no pattern there!

I do think she looks a bit cresty the years she is due to foal with a colt. This could just be my imagination.... She seems to be sporting the stallion neck this year, so only time will tell if I am right!

[JB]

Well, I think it's fun, but not true. My vet was betting my last foal would be a colt because we inseminated almost right on ovulation, and she says male sperm are faster swimmers. She has a theory that insemination closer to ovulation produces colts, further away produces fillies.

We were right on insemination--got a filly!

Heard of "beat the odds"?

Just because you got a filly in what would more likely have been a colt situation doesn't mean the theory is not true.

The male swimmers ARE faster, they DO die earlier. That's why insemminating prior to ovulation increases the odds of a filly - the girl sperm might be slower, but they live longer, and they're much more likely to still be alive and kicking by the time the egg comes along. That does not mean that in any given situation, there's a super-boy swimmer who makes it first.

In flipping a coin, statistics say you would get 50/50 heads and tails over enough flips. Just because you get 10 heads in your first 10 flips doesn't disprove that

[VirginiaBred]

Sort of unrelated but I remember reading somewhere that older stallions sired a higher percentage of colts. Something about nature selecting for a replacement for the aging herd stallion.

Hope that's true!!!