GENETIC DEAFNESS IN MINIATURE OVEROS

[RavenHawk000]

A very well-known professor at my school, Purdue University's School of Veterinary Medicine, Dr. Michele Levy, DVM, ACVIM, and chief of large animal medicine, is in the process of gathering participants for a research study that he is conducting regarding genetic deafness in overos. He is aware of the prevelance of this condition in miniature horses and is seeking miniature owners that would be willing to participate in the study that will most likely become a publication in a major veterinary journal in the near future. All participants would of course be kept 100% confidential and the procedure is minimally invasive. The study uses the BAER (Brain-activated evoked response) method which involves recording the brain waves that are created when a sound is processed.

So, please e-mail or PM me if you have a miniature horse that is overo or overo bred that you know is deaf or are suspecting is deaf. I can give you more details then privately.

This is your opportunity to contribute to the entire equine community in a big way ! :aktion033: Don't just sit back and let everyone else do the work for you !

 

[JennyB]

Hi,

I don't have a deaf overo, but my stallion was tested for deafness down at WSU in Pullman when he was just a baby. At the time in 1997 I had been chatting with a gal in Australia who said that most all overo's were deaf. She said, I should have mine tested as he was a max. white and so I did. He was not deaf, but had more hearing out of one ear than the other. It was the BAER test and was very easy and quick. I am not sure if you would like a copy of the report, but you can have it if you want ?

:

I understand that many splash whites are deaf, but don't know how many frames would be. I would be interested to know the results of this testing when finished. Thanks

My best,

Jenny

 

[rabbitsfizz]

Again, we need to open up the term "Overo"

The only lines to have had deafness proven in them have been Splash.

As with LWO the blanket term "Overo" is misleading

It is Splash horses that occasionally have deafness and which are though to have a defect linked to deafness.

So please everyone do not panic about "overos".

If you think you have a Splash foal that is reacting strangely it may be worth testing for deafness, but remember that early infant illnesses can also cause temporary deafness in foals.

ANY studies done on ANY defects or problems are worthwhile and should gain our support.

 

[kaykay]

Thanks rabbitf for clarifying that. Also keep in mind there is a particular bloodline in Australia that carries deafness in splash horses but they are big horses not miniatures.

 

[Frankie]

ANY studies done on ANY defects or problems are worthwhile and should gain our support.

I so agree, what better way to learn and be educated so we do the best we can for the breed.

 

[wcr]

I don't have any suspected deaf minis but did have a deaf paint foal at one time. He was maximum expression frame/sabino.

 

[Robin_C]

He was maximum expression frame/sabino.

I have a similar mare -- maximum expression sabino/frame -- who I would lay money on as being stone cold deaf. Neither of her parents were non-hearing, so I don't believe she qualifies as "genetically" deaf, i.e. following a line of similar affliction in the parents, but deaf nonetheless. I have contacted Nicole about her and even though I'm way down here in Florida will try to get her involved in the study some way or another to further the cause.

Robin C

 

[Firefall]

Is there any way to really tell if one is possibly deaf? How do the act?

I've heard this before and would like to know more about it.

 

[Robin_C]

Here is what I've noticed about my presumably deaf mare. I've had her since she was 4 months old and during that time:

1) She does not respond to loud noises in any way. Have tried banging things right over her head while she was eating and get not so much as an ear twitch. If she sees you, however, she will look up - so it's not a definitive test.

2) She acts startled if you approach her from behind and she does not see your shadow. When you come into her field of vision (which may also be compromised) she jerks her head up like - "Oh, there you are!" She may feel vibration as I walk, but doesn't recognize I'm there until I come close. She could be just really, really laid back, so again this is not a definitive test.

3) Her pasturemates shun her. While they aren't mean to her so much, they will leave her alone in the pasture and she is often found in one corner way off to herself before she realizes they have all gone. She does have one friend who was purchased with her that will sometimes seem to "look after her", but not always. She does not respond when called or to a shake of a feed bucket IF SHE CANNOT SEE IT.

4) She will stand in front of loud farm machinery, such as a front loader, without even batting an eye. Will graze right in front of it and act like it isn't there. Same thing with riding lawn mowers, the golf cart, etc. NOTHING frightens her. The other horses run to the next pasture to get away from the front loader, but not her. She'll stand right in front of it like a logging protester! You literally have to bodily chase her away.

I know that NONE of these are definitive proof that she is deaf, BUT it gives me a pretty good indication she is!

Robin C

 

[wildoak]

The deaf filly we had born here last summer was the first I'd seen and obviously different from the moment of birth, but it took me a couple of days to figure out exactly why. When she first stood, she circled mom repeatedly, had a little trouble finding the milk but not significantly more than others I've had. But mom's nickers did not get a normal foal response from her. This was a first time mom, so we weren't sure how much of the difference was due to her not knowing what to do, and how much to the foal. Didn't take long to realize that the filly just didn't respond to any outside noise. I tried sneaking up behind her, banging cans, etc and as Robin said, as long as she could not see me she didn't respond at all. She went home when she was a week or so old and I haven't seen her since, but they say nothing has changed.

Jan

 

[rabbitsfizz]

Millard Line is the line in Oz affected.

Since there is not test for Splash, are you sure these Max expression horses are not also Max expression Splash???

 

[Robin_C]

are you sure these Max expression horses are not also Max expression Splash???

I feel pretty comfortable saying that my mare is maximum sabino as sabino was clearly and abundantly evident in both parents who are both known to me. Nothing that really said "splash" to me, but I find this the most confusing of all patterns to pick out when it is in combination with others. I can identify it by itself, but when sabino + tovero (as in the dam's case, who is at least 50% white) or sabino + frame (in the sire's case, who is approx 75% white) I start to lose the ability to see splash characteristics clearly.

Robin C

 

[Lisa-Ruff N Tuff Minis]

at Nationals we were in a class with a horse who was deaf he wasnt a splash in fact I would have called him a sabino I think he was solid bay with a huge bald face might have had socks dont think he had any body markings he was so pretty.

She was in the line next to me so we had plenty of time to chat, such a beautiful guy and she told me he was born I think if I remember right at her farm and deaf from birth - didnt stop him from winning the class though(gelding class)

 

[rabbitsfizz]

Lisa a bald face and socks just about describes a minimal Splash- but I take the point that not all Splashes are deaf and not all deaf horses are Splash. It odes appear to be attached in some way to a pattern, though.

 

[Lisa-Ruff N Tuff Minis]

Well i hear lots of people argue that point but if that is the case I guess there is lots of splashs around

: bythe way my mistake I meant to say a blaze not a bald face..

:

 

[rabbitsfizz]

Rowdy had a blaze!! That's about all. He was registered as Sold Bay. He was LWO!!!!

 

[JO~*]

This was a horse that I had a few years ago and he was stone cold deaf.

Kinda wish I still had him, he wasn't afraid of anything as long as he saw it first.

 

[Lewella]

My first question is - if they are going to investigate deafness why not use the breed where the lines are known? The APHA has a much higher incedence of deaf Splash than the miniature breed. Gambling Man, a homozygous Splash, wasn't deaf but produced many deaf heterozygous and homozygous Splash offspring. Barlink Macho Man has produced deaf Splash. The Triple's Titan line produces deaf splash. The Mr. Gunsmoke line produces deaf splash. These are easily traced and well known and have large family groups to examine. The mechanism is going to be the same as in miniatures - the link is to the Splash white pattern (and the link has been know for a long time, but no one knowns why some Splash are deaf and some are not).

Jo - your former horse is a textbook example of sabino + splash. ANY TIME you see eyeliner like that you are looking at Splash and Sabino combined.

Minimal expression heterozygous Splash Whites and "normal" sabino markings can overlap greatly and sometimes when both patterns are present you won't get significantly increased white like is expected when sabino is combined with other patterns. Splash is an incomplete dominant - it needs to copies to fully express. Minimal heterozygous expression can be as little as a faint star.

In some breeds where Splash is known deafness is unheard of. Icelandics are an example of Splash that do not have deafness issues. (All "normal" markings on Icey's are caused by Splash - they do not have sabino in their gene pool).