Stallions - Herda Carriers

HERDA afflicted is a horse that has two copies of the HERDA gene. The site IS correct in that a HERDA afflicted horse bred to a noncarrier will produce all 100% carriers.

HERDA Afflicted horses are HRD/HRD. They only have HERDA genes to pass on. That is why a HERDA horse bred to a a nonHERDA (N/N) would produce carriers (N/HRD) everytime.

But only a percentage, correct? (PS- I have no intentions of breeding a HERDA carrier nor do I endorse it)

Nope, an HRD/HRD horse bred to a N/N horse will produce N/HRD horses everytime (100%).


N/HRD to N/HRD is 25% N/N, 50% N/HRD, and 25% HRD/HRD.

N/HRD to N/N is 50% N/HRD and 50% N/N.

Obviously N/N to N/N is 100% N/N (and HRD/HRD to HRD/HRD is 100% HRD/HRD)

This was the part that first got me confused becuase of this statement:

Breedings between normal and carrier horses will not produce a HERDA foal although 50% of the foals are expected to be carriers.

So that 50% you are talking about is CARRIER.

I know this gets into the hows and why's of breeding and the money thing but now I'm getting it. The breeder thinks... OK 50% chance it's a carrier but who cares because it's just a carrier and so they breed and then either get a mare or a potential winner so they show and earn titles, money and points and then... OH gee, breed again... and it may or may not be a carrier.

Ok... light go's on...

Yep. That is what it is. Carriers are not afflicted, they only have one copy of the HERDA Gene. Afflicted horses have two. A horse must have two genes to be afflicted.

Yeah, the whole point is that many of the top name breeders don't care if they are producing carriers or not. They breed their carrier stallions to hundreds of mares thus keeping HERDA going forward into the next generations. What I'm saying is that there are enough well bred performing stallions that do NOT carry HERDA, so I really don't see a need to use the carriers as breeding animals. That is not even counting the known carriers that aren't even alive anymore, but their collected semen is still being used!

Thank you for your patience with me Nd. I think I completely get it now. Saddly I am one of those that only know the basics on certain issues because they don't affect me. I have an Impressive mare (HYPP/NN) so when I decided to breed her I got HYPP smart because I had a need to know. With Herda - I had merely a basic understanding and I think I read too far into things and really confuse myself.

Very interesting topic Animal.

To me it is just one more thing to look at and think about when breeding. For me it is assigned a weight and that is all put into the decision process as to use a given stallion or mare or not.

There is no way I would ever say that no HERDA carriers can ever be used or registered. That is just not realistic.

We all tend to overcomplicate things and look deeper than is necessary...I do it all the time.

The hereditary genetics of HERDA are exactly the same as HYPP, so just apply your HYPP knowledge to HERDA. The only difference is a HYPP carrier can be afflicted, but a HERDA carrier cannot...it takes two copies of the gene to induce actual HERDA affliction...

Breeding carriers perpetuates the gene that causes the disease...there is no argument against that - it is a fact.

If no HERDA carrier were ever bred again, the gene would disappear completely in one generation...there is no argument against that
- it is a fact.

If everyone refused to breed carrier to carrier for now and all time, so the disease would never manifest itself despite the presence of the gene, then I wouldn't have an issue with breeding carriers to non carriers. This would let us have our cake and eat it too. But we both know that is not realistic either.

The darn problem is that while you and I and others may be knowledgeable and responsible breeders, we sadly represent a small minority of breeders. The vast majority of people that breed know little or nothing about HERDA, HYPP, SCIDS, and other genetic diseases, and don't subscribe to horse forums or other sources of information. What we deem as "common knowledge" is only common knowledge in the circles we run in...much of the world is either ignorant or just doesn't care.

That's why none of these diseases will ever be erradicated - poor breeders or breeders breeding unregistered stock with unknown ancestries. However, it is my opinion (and it is only an opinion), the registries should shoulder the responsibility to erradicate these diseases from registered stock. It can be done, and it can be done within the breeding lifetime of the horses now in existance - about 25 years. It is also my opinion that this should actually be a DUTY and a RESPONSIBILITY of the registries, which should be acting as stewards of their breeds rather than sitting around thinking up ways to increase their fee revenues.

You and I have always disagreed on this issue to a degree, although you know I don't condemn you because you know what you are doing. I just am personally more concerned with the bigger picture and consider the interest of our breeds more important than the interest of we owners and it bugs me that we don't eliminate HERDA and other horrible genetic diseases in our registered stock when it is easily within our ability to do so...