View Full Version : On the subject of melanomas

Jan Heine
04-03-00, 07:04 AM
Possibly showing my ignorance here but is the melanoma and grey horse a particularly Australian phenomomen? My new boy is a grey and when I bought him I did pass comment about not wanting to buy a grey because of melanomas - the guys in Ireland looked at me strangely and then I started thinking about all the grey horses I know in Ireland both young and old, mares,stallions and geldings - and yep couldn't think of any who suffered from this condition. There was one grey I was interested in 12 months ago but I was cautioned about him because he had an "hereditary skin condition" but it wasn't melanoma problems. So is it an Aussie thing because of our climate and if so does this mean we should look at ways of preventing it - such as perhaps boxing our grey horses during the day and turning them out at night - keeping them carefully rugged - but how does that stop melanoma forming around the anus? I am interested to hear - especially from anyone outside of Australia as to whether you have this problem too!

04-03-00, 08:03 AM
I find that very interesting, Jan.
A few facts for consideration, then I'll present my theory...

1 - the grey gene is a partial lethal, because it causes melanomas which can be harmful to the horse.

2 - as a grey horse gets older, the pigment (melanin) is held in the skin, not released into the hair, thus the hair loses colour and the concentration of melanin in the skin is higher.

3 - white or going white grey horses are not like fair-skinned people, their skin is blacker than that of a black horse.

So why do aussie horses get more melanomas?
If a grey horse is rugged it's whole life, is it actually less likely to get melanomas than a horse that runs around in the nude all it's life?
If melanoma is caused by the sun, why don't they get it in areas that get a lot of sun like the muzzle, as against under the tail?

Maybe it is coincidence that you don't know any greys with melanoma in Ireland. I know a stack of grey horses without them and only 2 (mares in their mid 20's) that do. Maybe it is talked up because of the nature of Aussie horse people (let's face it, we're passionate about our horses and there are plenty of drama queens about).
Maybe something in the sun (UV etc,) reacts with the melanin to cause the melanomas. It's no secret that we have stronger sun here than they do in the UK.

Personally I think it is a bit of a combination of the two. I'd love to research it, but I don't have the resources :-)

Jan Heine
04-03-00, 08:30 AM
That was what confused me about the sun being a factor Jodie - the fact that so many start under the tail - I do wonder too what causes it and whether it really is more prevalent here in Aus.I guess there are horses with it in Ireland but you see a lot more grey horses there (certainly in jumping) than you do here so I guess if it is a numbers game then it should be there as well as here. Interesting though - I wonder how you would go about finding out figures on prevalence of it!

04-03-00, 10:16 AM
I don't know what causes it, but from my experience, I don't think that the sun is a major facture. My horse was stabled constantly in his racing career prior to when I got him... since then, he was constantly rugged... rugs with a full tail flap.

I do think though that certain drugs can increase the melanomas growth, so be certain to double check with the vet....

04-03-00, 01:30 PM
It is also believed that some breeds and families of horses are more prone to it. Maybe the difference in the breeds between here and Ireland has something to do with it.
Seems to be a lot of TBs get it, maybe there are particular families of TB that are common in Aus that have the genetic predisposition.

Jan Heine
04-03-00, 02:17 PM
Ahh Jodie that makes more sense - maybe the Irish Draughts don't have it so much in their genetic make up - that would make a lot more sense- thanks for that! Yep maybe it is something t/breds are more prone to.