Monday, March 29, 2010

Intersex Horses?

I had an ad all picked out that I had planned on posting this morning. Then two things happened.

One, something is wrong with my Google Chrome Browser program. I've been using it for nearly a year and have not had ONE PROBLEM with it, until this last weekend. It crashes immediately upon opening. It crashes within 5 minutes. IT CRASHES every time I want to do anything!

So, while the boyfriend and I attempt to correct whatever problem Its having, I am forced to use Internet Explorer, which I absolutely can't stand. Now, because I don't use IE for much of anything, save one other program that requires IE to run, my homepage for IE is Facebook.

I went to open IE, and just had to look at my news feed for Facebook to see what everyone is doing.

And, came across one HECK of a mind bending article.

Article on Horse that is BOTH Genders!?

Story is about a Paint mare in Canada, that during her training started acting a bit odd. She would urinate on other horses manure piles, mount the mares in the pasture, and act well... like a stud. Owner stated that one day under saddle she'd be fine, the next she'd be completely wild and super aggressive.

So she had the mare checked out by her local vet. USUALLY super aggressiveness in mares is caused by problems with their reproductive system - most commonly with cysts on their ovaries that cause large amounts of Testosterone to be released. This isn't "Moody Mare" Syndrome where a mare in heat becomes super hard to handle. This is aggressiveness that is unrelated to any cycle the mare has.

Well.... the vet didn't find cysts during an ultrasound. Instead, he found a pair of internal Testicles! Hidden inside where her uterus should be! A trip to the University of Guelph's Ontario Veterinary College confirmed the discovery.

The mare's 2 sisters on the maternal side ALL had the same issue. No Cervix, no Uterus, outwardly a "she", but inwardly a "he". They have so far traced it back to the dam of all the affected mares. She has a mutated x chromosone that causes this defect in her daughters. This is where the genetics becomes both confusing and facinating.

This is my rudimentery understanding of genetics at work here.

Mare has X+X-. (I'm using the + and - here to illustrate the good and mutated genes for simplicity sake.)
Dam carries the mutated x gene, but is not expressing it. Thus she must be X-X+. When bred, the mare contributes the "bad" X- chromosome, the stallion gives one "good" X+ chromosome, and the resulting filly is again X+X-.

They cleared the stallions/sires genetically, so we know their X chromosomes are basically clean.

But in the filly, the symptoms with the mutated X chromosone become apparent from puberty on. So what makes the filly's X- chromosome different from her Dam's X- chromosome? I can't answer this but it sure is interesting to think about.

The article goes on to say that the ramifications for this discovery could be huge in the horse racing world, and goes on to mention 2 Standardbred Trotting mares that were found to have super high levels of Testosterone during the post-race pee test. Track officials thought that both mares had been doped up with "T", but with this discovery, that may or may not be the case.

I bring this up here, not just because I had NEVER heard of this before, but quite frankly, who needs another thing to worry about when you are condidering breeding your horses?

Intersex animals happen more often than you think. Dogs, goats, and yes, humans, all have instances where an indivudual is born outwardly one sex, but inwardly are the opposite.

The mare featured in the article underwent surgery to remove the testies, and the owner says the mare is now a completely different horse... she's the mare she should have been all along. Without any internal female reproductive equipment on any of three related mares, at least they can't reproduce and pass the gene on. However their dam still obviously can, and the University researchers are in the process to see if a test can be developed to single out the defective gene and identify it.

All I can say is wow. More defective genes in horses. More genes that cause mutated foals to be born. And once discovered in a horse, do you really think that horse will NO LONGER be bred? Sound Familiar? Lethal White Overo (OWLS), SCIDs, HyPP, HERDA... shall I go on?

How many more of these genes must we find before we realise we are destroying our horses gene pool? If the owners of these horses that carry these mutated genes would just stop breeding them, we could wipe the genes out and have a healthy gene pool once again.

AT least with this particular mutated gene, on the first breeding of the mutated gene passing on, and once symptoms show outwardly, one surgery to remove the testies 'cures' the problems, and the problem stops. The question is then, how many of our mares are carriers of this gene, and how many mares are suffering from the symptoms and their owners never ever get them checked out? How many mares that end up being sold as 'aggressive', or 'mean' are suffering from this very issue?

I'd like to hope not very many. But when HyPP first started to infect the gene pool, there were only a handful of Impressives direct offspring that carried it. Its a lot easier to stop breeding say, 10 horses than it is 1,000,000 horses.

Food for thought as we go about our day, for sure.


  1. That is very interesting. Did the original mare produce any colts? If so, I wonder if there is any chance they too carry the gene but in a recessive way. I am not a geneticist in any way so I am just curious.

    At least in the case of this one mare and her three fillies, it can be resolved, but I agree, how many more are there out there, whose owners never investigate thoroughly?

  2. The article only mentioned daughters out of the dam id'd with the gene. I'd be also interested to see if this affects colts as well. I don't think the research has gone that far yet. Hopefully this will in the future gain a bit more attention.

  3. There's something called a barr body that pretty much negates some of the genetic material in one of the X-chromosomes in females. I wonder if that's affecting this?

  4. Testes.

    This is pretty much a self-limiting mutation, as the affected offspring cannot reproduce.

  5. I'm in school for genetic engineering and i've heard about this happening before. Basically part of the Y chromosome gets transposed on an X chromosome when sperm is being formed in the male. The egg is fertilized with the sperm with the X chromosome. So while the mare is XX, it would be a male. But its SO WEIRD that it would come from a mare and not a stallion.

    Theres still alot we are still learning about what makes animals male or female... its not as simple as just X and Y... Its a pretty complicated feedback mechanism where everything has to be right, or something wacky happens.

  6. saying we should not breed horses with the OWL gene is rediculous, that would eliminate ALL frame overo horses which are beautiful. The OWL foals only result when 2 OWL carriers mate, so testing would eliminate the lethal foal, OWL bred to non OWL will not produce a lethal foal, EVER! example, overo to tobiano, no chance of a lethal foal, sabino to sabino, no chance of lethal foal, frame to frame, def lethal foal if it is a true frame.