Castration findings Nov. 9 2007 
Question 
In your research have you found any link between a mature colt (2+ years old) having 1 very large testicle and 1 small/normal testicle at gelding time and a pedigree that is known for producing dwarfs? 

Thank you for your time.  
Betty B. 

  
Answer 
No, 

That would be something to look at more for cryptorchidism alone. Even if your colt had both testicles descended. If the measurements of the testicles were outside of expected norms for size, either too large, or too small, you would look at cryptorchidism first, I would. It is well known that cryptorchid horses have one descended testicle that is larger than normal in size, when measured. And that the retained testicle is smaller than normal in size when it is removed. 

There are known dwarfism in humans that see cryptorchidism, but that is when the human is a dwarf, not a normal human and being crypt. A normal human and being crypt would be looked at as a cryptorchid first not a dwarf or a carrier first. I assume your horse is normal and not a dwarf. 

John  
 

How close are we? Nov. 9 2007 
Question 
Hi John, 

Thank you so much for answering questions for us. From reading your replies it appears that once the dwarf gene is identified and can be tested for we will be able to make much better decisions about our breeding programs. Similar to the LWO, if you have 2 carriers of dwarf you wouldn't breed them. My question is: realistically, how long do you think it will be before we identify the gene and then can test for it.  
Sandy 
Total Eclipse Miniatures 

 
Answer 
Sandy, 

It could be several months, it could be literally several years. It all depends on number of samples that can be used in early studies, amount of money raised for research, and how little sleep I can function on, I am the research lab so to speak. 

John  

A minimal dwarf and Nov. 9 2007 
Question  
John, THANK YOU for taking the time from all of us wanting to learn more about the betterment of our breed. I had a very minimal dwarf born out of a mare that I bought bred. When it came time to geld my little guy, (about 2 yrs old, and in good health) my vet refused saying he didn't really know what was all going on with him (???) but yet at the age of 5 years old without my vet realizing this was my minimal dwarf, he gelded. He was fully dropped at the age of 2. Could you please explain to me what problems he would of all come across gelding him earlier, rather than later? He had a bad bite, and a "barrel" belly, and was a little weak in his hind end, which he seemed to outgrow. I could understand if he was a severe dwarf, and had not dropped, but that wasn't the case. Is it common for a vet to wait with gelding a minimal dwarf and why?  
Corinne  
Meadowridge Farm 
 
Answer 
I do not know of any problems gelding a dwarf at 2, other than him not having both testicles dropped yet. I would think that if they were both dropped that he would not put him under general anesthesia, just sedate him and cut. I just think he didn't want to do it or was afraid he would kill him by accident and be sued. 

John 

Genes 
Question 

If a specific gene has not been isolated, how do we know for sure that there is one, and that some horses are just carriers? 

Do you believe that a dwarf can be produced if both parents are non-carriers, and normal horses? And by that, I mean, are some dwarfs produced because environmental factors or trauma during pregnancy, like if the development and growth were disturbed by some factor other than a gene passed from a parent? If this is the case, will it really ever be possible to have a dwarf free breed?   
Matt Drown 

Answer 
"If a specific gene has not been isolated, how do we know for sure that there is one, and that some horses are just carriers? " 

It is called population genetics, I advise you get a book about it, in there it will explain about genes and generational large-scale inheritance patterns with respect to dominant and recessive genes. 

How did researcher's years ago know that in humans there are different blood types and there are specific inheritance patterns of those types???? and this was before DNA testing. 

There is a mountain of information about inheritance of recessive genes and how generations can go on before it crops up. 

I think you need to read some basic genetics books and specifically read about inheritance of recessive genes, because you just answered your own question. I am not making these terms up or these known genetic inheritance facts. These are genetic rules that have been scientifically proven. I applied genetic laws to my study and it fits. 

Recessive genes exist in all living organisms even bacteria and viruses. They are not expressed unless certain conditions are met. This can be either by reproduction of the organism and the resulting offspring inherit it or like in certain bacteria can live in certain changing environmental conditions. 

 And no, dont get the idea that dwarfism is a gene that can willy nilly turn on or off, it is not that kind of gene. There are those kinds of genes in us, yes, called regulatory genes of certain pathways, metabolism, digestion, etc. 

If you are a carrier of a gene you have the gene in your DNA and can pass it on to your offspring. 

"Do you believe that a dwarf can be produced if both parents are non-carriers, and normal horses? And by that, I mean, are some dwarfs produced because environmental factors or trauma during pregnancy, like if the development and growth were disturbed by some factor other than a gene passed from a parent? If this is the case, will it really ever be possible to have a dwarf free breed?" 

Two non-carriers (proven) will not produce a dwarf of that gene they are NOt carrying. If they are non-carriers of one type, yet are carriers of another type, they could have a dwarf of the other type they carry. 

I have not read yet anything about dwarfism being caused by trauma, do you have a specific type of trauma you are thinking about???? 

Well I will say there are no dwarfs in the Shetlands that I have seen documented, or the Hackney, or the POA, or the Arab, or the Welsh, or Caspian, Dartmoor pony. I don't know, how can they have breeds without dwarfism?? Maybe breed better horses?? 

Someone PLEASE bring me an example of your dwarf caused by an environmental factor, that you can definitively say is just that. I will never say that no unusual random event can't happen to then cause a dwarf. On the contrary, how do you think genes can get mutated, they mutate due to random events or influences. And no don't think that all these dwarfs are caused by random events causing the same gene to be mutated. 

I would challenge anyone to find dwarf Miniature horses that they can prove was caused by a single common environmental factor all over the world that could be proven as the reason why we have all of these dwarf horses. Please go my son, make me proud. 

What I am trying to teach you is that look at your population of Miniatures, in all areas of the world. Now look at all the different environments they are in, now look at all the dwarf type 1 only that are born. Now, you tell me that one specific type with very similar characteristics have a chance of being caused by something in the environment, ALL OVER THE WORLD. Which also would need to be in the exact same conditions. If just one of these dwarfisms was caused by even just 1 environmental factor, you would need a super computer to figure your odds to prove it is NOT being caused by a gene. This is because of the billions of variables because these dwarfs occur all over the world. The odds are tremendously in my favor of it being a recessive gene.  
John 

Environmental Birth Defects That Mimic Dwarfism??? Nov. 12 2007 
Question 
I think from your previous answers that you have made it very clear that you do not believe that environmental factors are the cause of the gene mutation/s that cause dwarfism. 

However, is it possible that environmental factors can disrupt normal fetal development and cause 'environmental' birth defects that manifest themselves in the same TYPE of deformities that we see caused by 'genetic' dwarfism (ie: limb deformities and undershot jaw, etc.)? I am thinking of things like nitrate poisoning which was believed to be the possible cause of birth defects in some Canadian horses. 

If environmental factors can cause developmental birth defects that have many of the same outward deformities as genetically caused dwarfism, how can a breeder determine if their foal's problems are from genetic or environmental causes? 
R3 Minis 
 

Answer 
R3, 
Below is the link from Canada making a notation on the theory of hypothyroidism in smaller horses possibly due to nitrate toxicity. Thyroid function, normal or abnormal, influences the growth of all animals, this notation in the Ontario website describes rather poorly and generally a PROPORTIONATE dwarfism. The dwarfisms I am researching are categorized as DISPROPORTIONATE dwarfism. 

Proportionate dwarfism refers to the "shrinking" of everything in proportion, including bone size. Disproportionate dwarfisms are NOT like that, they have certain bone growth that is abnormally "shortened". Malformed elastic or restricted joints due to underdeveloped bone from cartilage. Shorter long bones than should be for their size, BUT this is due to the disease affecting the LENGTH of the bone growth. That is the part of growth that is restricted. 
 

In their description they describe generally, small PROPORTIONATE horses from small horses (possibly Miniatures or Shetland, don't know, they don't say). They go on to generally describe the foals as with musculoskeletal IMMATURITY, NOT shortened elastic or restricted joints. Meaning very refined, structure, i.e.. immature or premature looking. They also describe delayed cuboidal bone development, which is a bone in the lower legs of the horse, this description would in plain terms be immature cuboidal bone causing hyperextended joints, or weak legs and joints, like an underdeveloped foal. A large head is listed but not described in detail, and if it were severely domed I would think that would be mentioned. 

Floppy ears are listed and I do not know of that as being a known common characteristic in dwarf foals in the Miniatures. I see the ears set back on the head due to the head's domed shape but not "floppy", they function fine. 

Mandibular brachygnathia means the foals had a severe OVERBITE, that the lower jaw is underdeveloped. That is not what is seen in the Miniature dwarfs which is an underbite, that is a characteristic quite common in the dwarfisms I am studying in the Miniatures. 

Quote from a different section of the same website from Canada 

"Brachygnathia refers to a malocclusion between the mandible and the maxilla. Mandibular brachygnathia is most common and refers to an abnormal shortening of the mandible which results in an overshot upper jaw or parrot mouth." 

They did not give a reference paper or article, so I do not know where this informatin has come from. 

They also strongly recommend testing thyroid levels and nitrate levels so as to not OVER diagnose this disease due to supposed low thyroid levels due to nitrate toxicity. 

I am assuming this is the Canadian article you are referring to. 

http://www.omafra.go..._congenital.htm 

Quote from the website-- 

"Dwarfism refers to the failure of appropriate growth resulting in a smaller horse. A dwarf horse can be proportionate or disproportionate. Proportionate dwarfs are a result of a deficiency in growth hormone while disproportionate dwarfs result from abnormal thyroid hormone levels. The latter results in a foal with musculoskeletal immaturity, characterized by delayed cuboidal bone development, a large head, silky hair coat, floppy ears and mandibular brachygnathia. Determination and interpretation of either growth hormone assays or thyroid hormone function is not entirely developed or understood in the equine, hence the importance of clinical diagnosis. Efforts towards characterizing thyroid function and growth hormone levels should be undertaken to prevent overdiagnosing this condition. A nitrate toxicity theory has been confirmed in certain foals born with "congenital hypothyroid syndrome". " 

Below is a PDF file that you can open that lists in general terms and descriptions different types of dwarfisms in humans. It is very strait forward, so you should be able to read and distinguish the descriptions between the many types of dwarfisms. 

BTW, Achondroplasia and other similar types of dwarfism are referred to as DISPROPORTIONATE dwarfism. These are the types I am researching and comparing to the Miniatures due to the physical similarities in which they manifest themselves. 

http://www.tahperd.o...ts/Dwarfism.pdf 

I want to again try to explain my opinion, I strongly feel these types of dwarfisms I am working on are genetic in nature and NOT environmentally induced. The chances of a specific toxin in the environment, be at toxic levels ALL OVER THE WORLD, to produce this high number of dwarfisms is very scientifically unrealistic. If nitrates were that toxic all over the world you would see MASSIVE congenital malformations and deaths from numerous other animals including humans, not just our little Miniature horses. 

BTW nitrate toxicity is relatively a low-level toxin to horses when compared to sheep and cattle, due to the different digestive tracts, ruminants vs monogastrics, meaning it takes a higher level to affect horses than it does cattle or sheep. However, horses are more susceptible to nitrate poisoning than other monogastric animals due to the cecum. Below is a website about pollutants and ground water, where this info above came from. 

http://www.soil.ncsu...acts/AG-439-14/ 

I have done quite extensive searches for anything reported or documented, describing any type of birth defects from Nitrate poisoning that mimic DISPROPORTIONATE dwarfism. I have yet to find any. If you have any information describing any credible documentation with pictures or physical descriptions of horses being born with disproportionate dwarf characteristics from nitrate poisoning, I would really appreciate you sending it to me.  

John

Nitrates again Nov. 12 2007 
Question 
Below is a link to an article written that gives a slightly different description of the affected foals with congenital hypothyroidism due to Nitrates. This article describes them with an underbite. And also notes references. Does this sound disproportionate? Thank you for taking your valuable time to help us all learn more about dwarfism. 

Congenital Hypothyroidism in Foals 
Judy 
Judy Zachary 
Zachary Farms 
 

Answer 
I think you need to refer to my last thread about nitrates and review the websites I refer to for explanations on disproportionate dwarfism. 

Ok so now someone says it causes underbites as well, that is not surprising, since the toxin is affecting the abnormal growth and development of the mandible. The foals still do not have a severe domed head, shortened and malformed long bones of the legs. All of those photos are of big horse foals with normal length to their leg bones, the only mini is the little black Miniature foal. It looks normal and it is saying it is immature?????? Immature to what? a large horse foal?? They show no comparison of another Miniature foal that is "mature". I will say his ears sure are not "floppy", they came up for the photo. I have yet to see a Miniature dwarf of the types I study to show any of these symptoms only and nothing else. All of mine show very abnormal leg bone growth as well as hip, spine, jaw, and head malformations, etc. 

Unless I am blind I do not read anything that states that this is causing disproportionate dwarfism to the long bones of the foal's body or that it even causes any malformations of the head other than to the mandible causing an underbite. 

Underbite is a known inheritable genetic defect as well, totally on it own with no other malformations to the foal. If you look in any equine conformation handbook or breeding reference manual they clearly state that underbite or "monkeymouth" is an inheritable genetic trait that is undesired regardless of anything in the environment or other genetic or congenital defect that could cause it as well. 

What if the underbite wasn't due to the toxicity but was a genetic defect the foal inherited, are they sure it is only due to nitrates. All of the other nitrate toxicity documents I have read all refer to parrot mouth as one of the signature characteristics 

If you go to the bottom of the pdf. You will see this hyperlink below to the thesis paper of the reference Dr. Andy Allen. In this paper it very clearly states the region of the country Western Canada, Western Ontario, and Northwestern US, that are shown to be affected. They do not state this is occurring all over the world in mass. 

http://library2.usas...0212004-000356/ 

He clearly states the variables involved and that this was a case-controlled study, i.e., these mares and foals were Guinea pigs for this experiment, and were fed a very high level of nitrates. I can make just about anything I want to happen congenitally with any given experiment of a specific toxin. This was an experiment, this was not an out in the field study of what is really going on. They clearly state that certain examples were seen in that region of the countries and they suspected nitrates as the cause of certain congenital deformities, so they did an experiment to show what nitrates can do. 

It is starting to sound as if some of you are taking a known toxin and its effects on fetal growth and blanket applying it to any abnormality you see in the Miniatures, genetic or not. I dont get it. I am not saying there are no cases of hypothyroidism in the minis, on the contrary I know it exists, as it does in other horse breeds. And I am not saying that there arent any cases of Nitrate toxicity in Miniatures, on the contrary I am sure it has and will happen, but to blame everything wrong conformationally, congenitally or genetically in the minis on Nitrates is really not thinking things with a rational, critical mind. Are we going to blame all of the dystocias and foaling problems in the Miniatures all over the world on Nitrates too, and ignore their size as probably THE major factor?? 

I know of other toxins, drugs, etc., that can cause similar physical characteristics that are shown on that pdf. I just dont see how you CANNOT distinguish between characteristics of different diseases whether genetic, congenital or environmentally induced. There are differences in their etiology I will not go into here about all three. I would be literally writing a book. 

I am not belittling this toxin, I just do not see a single glaring similarity other than a slight under bite in one photo, the head is even normal in shape, and it is a large horse foal, not a mini. Dwarfs have numerous other characteristics that do not coincide with nitrate toxicity. 

John  

Dwarfism in combination with nitrates?  Nov. 12 2007 
Question 
I have had personal experience with congenital hypothyroidism in horses, in both Morgans and Miniatures. 

The first incidence was in 1991 with a Morgan filly. At that time little was known about what causes the condition. Research was in its very early stages, and at that time there was no idea at all that nitrates were the culprit. At that time, I talked with Dr. Andy Allen of WCVM in Saskatoon and he told me what he did know of the condition. Our Morgan filly did have a slight underbite at birth. She grew out of that in several weeks. There was absolutely nothing dwarfy about her otherwise; she was of normal size and proportion. Ears, nostrils, everything was normally sized & properly placed! 

Our second experience was in 2004, with Miniatures, when we lost 50% of our foal crop--the foals died within an hour of birth. Both foals looked completely normal, but they were born very weak & died without ever getting up. They just faded away. That same year another Mini breeder also had a number of foal losses, due to the same cause. In both cases it was determined that there was an iodine deficiency, probably combined with a nitrate problem in the hay, in the mares. This other farm also had losses of weak foals, plus they had several dystocias and several foals that lived but had extremely weak legs. With time the weak legged foals did come right. 

In 2004 I again talked with Dr. Andy Allen, and that is when I learned that he has come to suspect that nitrates are the root cause of congenital hypothyroidism. If the mineral balance is right the mare may be able to overcome the nitrates, but if the minerals are wrong the mare's system cannot compensate for the nitrates. We have since fixed our mineral imbalance. 

In this general area there have been many farms that have suffered foal losses due to congenital hypothyroidism--most have been full size horses, of all breeds--QH, Morgan, TB, warmbloods. Symptoms seem to vary in severity (in terms of weak legs and immature joints) None of the breeders I have talked to have described any dwarfism symptoms in their affected foals. The last time I spoke with Dr. Allen I specifically asked him about the dwarf type deformities people on this board have described and said were associated with nitrates. He said he hadn't seen any such deformities in the foals he has studied--the "deformities" he described to me were the same as what I have seen personally and had described to me by other breeders in this area. Remember, the other Mini breeder that had this same trouble in 2004 did not have dwarfism symptoms either--the symptoms in her Mini foals were exactly the same as have been seen in the big horse foals in this area, and as described by Dr. Allen. 

So, I have wondered, and this is my question...is it possible that with some Minis, where people are convinced that nitrates are to blame for the dwarfism that has shown up in some foals--is it possible that in some cases where the dwarf gene is already present the nitrates make the dwarf genes express themselves in a severe form, whereas without nitrates present it might have been a very minimal dwarf? I'm not saying all cases of Mini dwarfism, I'm just thinking that in instances where an owner insists that nitrates caused the dwarfism, because when the nitrate problem is corrected the dwarfism disappeared? 

I'm not sure I'm expressing my question very well...I've just wondered if in Minis there's more than one factor at work in some instances--if nitrates can cause maximum expression of a dwarf gene that would ordinarily remain hidden or minimally expressed? 

Thank you! (John, I'm very much enjoying reading your replies to all of these posts!)  
Mimimor 
Holly  
Cedar Plains Shetlands and Miniatures 

Answer 
Minimor, 

Please read my post I just did to the thread Nitrates Again. I go into great length discussing Dr Allen's thesis paper with regards to hypothyroidism and its characteristics. 

That said, your question IS very valid. Yes, there is a DEFINITE chance that Miniature horses born or raised in the affected areas and are carriers of the dwarf genes can have a dwarf affected by hypothyroidism from Nitrate toxicity and show characteristics of both diseases, one due to environment and one due to genetic inheritance. OF COURSE, THAT CAN HAPPEN. I APPLAUD you for having the resourcefulness to look into those things on your own, and critically examining the situation. 

I have been adamant about my position because not a single person has yet to ask your intelligent question, every one of the questions posed so far have been to blanketly blame nitrates for the dwarfism regardless of the fact that the vast majority of the nitrate toxicity characteristics look nothing like the dwarfisms seen in this breed. One characteristic of one disease does not make it the same disease for something else with the same one characteristic. 

I guess all people with club feet are dwarfs since that is a characteristic of some dwarfisms in humans. That doesn't sound rational to me. 

Dwarfism inheritance and expression is independent of Nitrate toxicity, one can have both and one can have either or. What you would see are the characteristics of both expressed if you have a dwarf with nitrate toxicity and some things will be compounded in severity, BUT Nitrate toxicity in no way will make the dwarf gene show up more often in homozygous form to cause a dwarf. Apples and oranges, recessive diseased gene and environmental toxin. 

For someone to not have a dwarf since fixing the nitrate problem, they either no longer have the carriers or they are having a great session of Russian Roulette so far, and their number isnt up yet again. The percentages are still there with the same horses to have a dwarf again regardless of Nitrate toxicity. 

John

Well there is finally research being done. Nov. 12 2007 
Question 

John, not sure if you will answer this? 

How do you believe we can protect our breeding program, until the research is complete and hope for an answer? 

 Should we stop completely breeding two minis that have a dwarf? or just stop breeding that Stallion with that Mare? I do understand it takes both to produce a dwarf? 

So, in my small herd that if my stallion and one of my mares produced a dwarf, I believe, I would sell the mare first and then think strong about gelding my stallion. 

But if I have been breeding a stallion from young to old, and keep the same mares breeding year after year. & no dwarfs. That does not guarantee they are not carriers and show up in their offspring correct? 

Thanks for the info a lot to take in and what is best for the breed.  
Wish you the best in your research.  
Rebel 
Mary Kavelman 
Kavelbel Miniatures 

Answer 
Reble, I had a nice rather long answer and I was kicked off and lost it all, so I will try to answer you again from memory. 

   How do you believe we can protect our breeding program, until the research is complete and hope for an answer? 
Those are choices you will have to make, I am not in a position to tell you what to do with your heard, those are things that you will have the ultimate say. It would depend on your size of operation and financially how involved you are in the carriers and the risks. 

  Should we stop completely breeding two minis that have a dwarf or just stop breeding that Stallion with that Mare?  
Those are your horses, again, I do not have the right to tell you what to do, Just as I would not want someone tell me who I can or can't breed. Mare could be used with a different stud that has not had a dwarf, but then again who is going to be honest with you on that?? 

Your stud would depend on your size of program, invested monies, again, those are decisions only you can make, not me. 

  I do understand it takes both to produce a dwarf? 
yes 

  So, in my small herd that if my stallion and one of my mares produced a dwarf, I believe, I would sell the mare first and then think strong about gelding my stallion. 
Again, investment cost versus breeding program size, and losses of foals that are dwarfs, all those play into decisions by small and large operations. 

  But if I have been breeding a stallion from young to old, and keep the same mares breeding year after year. & no dwarfs. That does not guarantee they are not carriers and show up in their offspring correct? 
It depends on how many foals the stud has had and how many mares that are carriers were bred to him. The more carriers bred to him and no dwarf foals, the quicker you can calculate his chances of being a non-carrier with a high percentge.  

John 

To breed or not to breed that is the question. Nov. 12 2007 
Question 
If what I am reading is correct no matter how many foals one has that are non-dwarf out of a certain mare or by a certain stallion there are no guarantees that the next one couldn't be a dwarf is this correct? At what number do you consider your herd or stallion or mare non-carrier. 5 foals 10, 50? 20 years? 

3 years ago we had a mare who had a dwarf she came to us bred I was on the fence about breeding her back and my vet suggested to try my stallion with her so we did and she did not have a dwarf BUT she did have a foal born with no eyes which according to the vet was also genetic or a gestational development problem so we have not bred her since and I have taken her out of the brood mare band, 

My question was this the right thing to do since she has had 2 problems back to back? Do you feel a mare should be taken out of the gene pool if she is a known carrier and if you don't think so could you give the reasons why not?  

Backwoodsnanny 
Nita 
Maine Pride Miniatures 
 
Answer 
If you breed your stud to 25 or more known carrier mares of one type (not guesses on looks), and no dwarfs of that type are born then your percentages of that stallion not being a carrier is in the mid to upper 90's percentage wise for him not to be carrying the dwarf type that you are looking for. Each dwarf type most likely is independent of the others, so you would need to do that for the others as well to be certain he is carrying none of the defective genes. 

If you breed 100 mares that are carriers and no dwarfs you are in the 99.999...... % chance of not being a carrier, it is not linear, it is a curve to infinity basically. 

Age is not a determinant, it is the number of unaffected offspring from specific mares. 

As for the mare, the dwarfism yes that is a concern, the microphthalmia I am not as concerned, YET. There are some thoughts of it being genetic, the predisposition to have small eyes, there might be an environmental influence, do not know yet. Right now, it is thought to be congenital with unknown etiology. Haven't looked into it that much, yet, not much time to do side stuff. 

I do have a microphthalmia miniature sample, from a foal, it died, and it is common to have other problems causing death. 

So, to use her or not that would be your decision. 

John

Breeding question Nov. 12 2007 
Question 
If you breed a stallion and a mare and they produce a dwarf..(so you know they both carriers, right?) then you breed the stallion to ANOTHER mare and have a normal foal..what is the percentage possibility that the offspring is a carrier? Thanks  
littlesteppers 
Christine 
C&D's Little Steppers 

Answer 
  "If you breed a stallion and a mare ..and they produce a dwarf. (so you know they both carriers, right?)" 
Yes 

  "then you breed the stallion to ANOTHER mare and have a normal foal..what is the precentage possibility that the offspring is a carrier?" 
Depends on if the mother to the normal foal is a carrier. If the mother to normal foal is a carrier then the foal has a 67% (2/3) that the foal is a carrier and 33% (1/3) chance the foal is homozygous normal. 

I hope you understand that if the foal is NOT a dwarf then you take out 25% of the chances you would before conception. So therefore, your calculations on the foal being a carrier only involve the 75% that are normal looking. 

Now if the mother is a non-carrier, then the foal has 50% (1/2) chance of it being a carrier, and 50% (1/2) chance of it being homozygous normal. Because if the mare is NOT a carrier, then you will never have a dwarf with those two being crossed. 

All of this assuming we are talking about only one type of dwarfism. 

John 

Pictures of Minimal Expression Dwarf? Nov. 13 2007 
Question 
Here are the pictures for the horse I sent you the pedigree. She has an underbite, club foot, long in the back (to me anyway) and head is just not right. approx. 29" I have always felt she was a minimal expression dwarf. 
kaykay 
Kay Baxter 
Baxters Painted Pasture 
 
Answer 
kaykay, 
I looked at the pedigree, and looking at the mare, nothing screams that she is recessive. That is far from saying she is a non-carrier, she has a possibility of being a carrier. Her Grand sire on the dam side never had a dwarf, but that is 2 generations back, a lot of other genes are "in" your mare, she only has approx 25% of his genes. The other horses close in her pedigree I do not know about. 
 
Her conformation is not ideal. That has nothing to do with dwarfism. Her underbite, I cannot determine in this manner if her underbite is genetic or due to lack of care with regards to her teeth. If it is genetic, it could be due to dwarfism expressivity or it could be just that she has genes for having an underbite. Don't confuse bad conformation or independent inferior genes with dwarfism expressivity over the dominant normal genes. In other words, some horses have less than ideal conformation independent of possibly carrying the dwarf gene. Clubfoot does not necessarily have anything to do with dwarfism, I think I expressed that in another thread. Clubfoot can have numerous causes including lack of proper hoof care, or bad leg conformation, independent of dwarfism influence. Yes, she is a little long bodied for her leg length, but that again really has nothing specific to do with dwarfism. 
Sorry I wish I could give you answer more specific. 
John  

Height Reduction Nov. 13 2007 
Question 
John, first of all thanks for being here and opening this forum to questions. 

I understand that dwarfism is not essentially about height, however - if I breed stallion A to mare B and have offspring smaller than both sire and dam, does that indicate the involvement of a dwarf gene, or is it just random height fluctuation? If you add to the equation the pretty but somewhat domed head and large eyes that we see often in this breed but assume a correct bite and no other dwarf features, does that affect your answer?  

Thanks, 
wildoak 
Jan   
Wildoak Farm 
 
Answer 
"if I breed stallion A to mare B and have offspring smaller than both sire and dam, does that indicate the involvement of a dwarf gene, or is it just random height fluctuation? If you add to the equation the pretty but somewhat domed head and large eyes that we see often in this breed but assume a correct bite and no other dwarf features, does that affect your answer? " 
 
You are correct, height has a high rate of variability with respect to carriers just as it does with non-carriers. If a foal is born to 2 parents and ends up being smaller than both, I would be curious about that but you would need to look at other offspring of both of those parents, ie does the stallion have a majority of small foals with less influence from the dams. Does the mare always have foals smaller than her, etc. Those questions do not help you rule out the foal being recessive completely, but you could look at it as if the majority of the stallion's foals are small then you would look at the smaller height as normal genetic variance and not due to a recessive dwarf gene the foal has inherited. Same thing for the mare. The head is something that is so variable, I do not rule by it. Exotic head with a pedigree that is known to have dwarfs, that is a concern.  
John 

Are dwarf carriers less prevalent in some miniature horse lines? Nov. 13 2007 
Question 
John, thank you for taking the time to share your knowledge and research with all of us. 

The majority of horses in my breeding program are Gold Melody Boy or Orion Light Van Huttenest bred with a sprinkling of Jandts, Eygption King, and Blue Boy mixed in. I have never had a dwarf foal but haven't been breeding for that long of a time. Am I just lucky or are there some lines of mini's that are at less risk for producing dwarf foals or carrier foals and if so can you tell us which ones?  
Thanks, 
Angelheart 
Maryann 

Answer 

Maryann  
I can't answer that, I cannot tell you specific bloodlines, I am in the middle of my work, I would be accusing a line of something with no scientific proof to back it up. I will only say that there is a very good possibility no one is free from the types I have seen. 
John 

Minimal Dwarf ? Nov. 16 2007 
Question 
Thank you, John, for sharing your knowledge on dwarf miniatures & your commitment to find the answers. It would be wonderful to have a test for the dwarf gene.  

Question ~ If you have a stallion or mare that produces a minimal dwarf are they likely to produce the typical dwarf with the bad bite, large head and crooked legs?  Where can we find more information on the "types" of dwarf genes?  

Thank you for taking so much of your time to answer all of our many questions. We can all benefit from your knowledge to improve the miniature horse.  
Nancy G 
Nancy Goshorn 
Galloping G Miniatures 
 
Answer 
  ~ If you have a stallion or mare that produces a minimal dwarf are they likely to produce the typical dwarf with the bad bite, large head and crooked legs?  
Where can we find more information on the "types" of dwarf genes?  
To try to bring some rational understanding to this subject about "minimal dwarfs", I feel I need to comment about the term, what it means and its use. 
 
First of all, the term "minimal dwarf" is totally a made-up term by someone somewhere that wanted to say that a horse that wasn't a dwarf but looked like one was a "minimal dwarf", or wanted to say that a true dwarf that was minimally affected (ie a good dwarf) was a "minimal dwarf". So needless to say, the term has been widely used for a wide variety of "good dwarfs" or "horses with really bad conformation" or "a horse that had an extremely exotic head, bad legs, and really small in height". Any way you look at it, the term has been used to try to describe a wide variety of horses with "some sort of problem." So, with that said, I strongly feel the term is incorrect and it is used improperly to describe certain horses. 
 
If you have a dwarf that is "a good dwarf" in the sense that it has the disease but it is not as severe in showing its characteristics, then you have a dwarf with two homozygous recessive genes showing less gene expression than might be typically seen. Your dwarf is no less of a dwarf than someone else's dwarf that might be more severely affected by its genes' expression of the disease.  
Unless you are looking at two different types of dwarfism, then you can't compare at all, because the pathology of the two diseases are different.  
 
If you have a very small horse with an exotic head, bad legs, and maybe other conformational faults, how can you say the horse is a minimal dwarf?? Don't you think it is possible to have all of those characteristics and NOT be a dwarf, (especially in this breed). That is not to say the horse is not possibly a carrier. If that IS the case, which you don't know until it produces one, then you have a carrier that is having expressivity of a recessive gene competing with the dominant gene. BUT, the horse is NOT a dwarf in having the characteristics of the disease. I have personally seen "really good dwarfs" and horses with expressivity of a recessive dwarf gene look very similar. So, until there is some real information to categorize these horses with certain traits and variances, I recommend to everyone not to use the term so loosely. 
 
So, to answer your question in a lengthy way, I do not know if the "minimal dwarf" a stallion and a mare have is actually a minimal dwarf and not a really bad horse, I don't have pics to see. I have seen thousands of pics of various horses over the years. I have learned to "see" certain characteristics of horses that might be expressivity of a recessive dwarf gene. But that does not mean the horse is a "minimal dwarf", it is no such thing. A horse with small size and an underbite does NOT classify the horse as a "minimal dwarf". An underbite is a deleterious trait all its own, without dwarfism causing it. Crooked legs on a small horse does not mean it is a minimal dwarf, crooked legs are in every horse breed. Our breed sees more of them because the size of the horse is not 1500 lbs. A large horse foal or yearling with severely crooked legs gets put down, we seem to let it go try to "fix it" and keep those alive, not because it is trying to be caring or that we try to breed for it. But, because of their small size they CAN still walk, run and breed, we keep perpetuating certain deleterious characteristics that are getting confused with dwarfism.  
 
So, I cannot tell you anything about if a stallion or mare that produces what might or might not be a dwarf, that actually later produce a dwarf. They probably have a possibility. I do not know the quality of the stallion or mare, I do not know the characteristics of the "minimal dwarf". So, when you give me very limited information I have to qualify my answer. I wish I could be clearer and not this vague but I can't. 
 
I can't really give much information over the internet about my work or the types with pictures or possible candidate gene homologies, with all that I have done, and the limited amount of work one person can get done in a lab at any given time, a large biotech lab could easily get the info and dedicate an entire group to it and scoop all my work, get the answers and get it out, and all my work since 1993 is gone, and I dont have a thesis to defend. I present my work to certain groups with enough information to grasp the enormity of my undertaking and try to help them understand what we as breeders can do now to try and breed better horses until some answers are known. 
John

Research facilities Nov. 19 2007 
Question 
John, I commend you for taking on this monumental task of researching & trying to isolate the Dwarf gene.  

My question is... Are there any other organizations who are researching Dwarfism, or who have shown an interest in researching Dwarfism, who might benefit from your research? I fully well, understand why you would want to "protect" your work until it is published. But, it has occurred to me that a big research facility may be able to get more funding & have a number of researchers working on this enabling them to come up with answers much sooner than one person can. Or, is this something that Equine Research just don't feel deserves the time, money & effort? 
Dona 
Dona Neargartner 
Kickapoo Acres 

Answer 
No research facility whether private or connected with a school is going to do any research on something like this unless they know they can make money on it or recognition for its discovery. That does not even mention the money these labs would want to cover costs for that research, or all the samples that would need to be donated, because they are not getting mine! 

I don't think you realize no research is done in these facilities for free. Who do you think pays for all of the costs???? It is paid for by the people that want the answers. The facilities ask for donations whether public or private, grants, government funding etc, the facilitiy does NOT pay for it out of their own pocket. Why do you think there are telethons on TV for certain human diseases??? Special colored ribbon fund raisers, ie breast cancer. There is not a research firm out there with Billions of money in the bank waiting to spend it on some research of some disease in the CHANCE they could profit from it. Someone else is going to take the financial responsibility and risk NOT the research firm. 

Also, there is no one in this breed knocking research facilities doors down with money wanting this work done and answers to this problem. I don't see the members of either registry jumping up and down with large amounts of money in hand willing to give it to any research facility. And large amounts meaning 10s of thousands closer to 100s of thousands of dollars, not a couple thousand that has been donated to UK or TAMU. The amount donated so far will pay for about 10 primer sets of potential microsatellite or gene sequences, that is, it. That doesn't include the other chemicals needed to even use them, or the machine run time to analyze the results, and those primers are NOT the genes with the answers to the dwarfism, very simply primers are things used to amplify or read DNA. 

Right now, there is another student in my lab working on a color gene to try and find it and make a test. It is very hush hush, why, because of potential that some other lab will beat this lab to the answer and the potential of recognition and money. Infact I have donated some Mini samples to be in this research that I feel are a specific color. I have also donated some samples when the research was being done for the Silver dapple gene for non-breed specific confirmation of the test. 

I have spent a very long time with my work, I know the pedigrees and its problems, I know the breed history, I know the different types of dwarfs seen, I have the samples. This is my work, I am not going to give up all my work to give it to some lab that only cares about making money on the results and not what all comes with those results, meaning what does this breed do with the answers. I for one appreciate those concerns. No lab with making money on their mind is going to care at all. Anyways, no lab is interested, if they were they would be knocking on our door. We have not shown that there is any money in it to be made. 

Now that I am here at Gluck I am involved in a lot of potential things that will help me find the answers, things I can't disclose due to confidentiality with genetic software developers to be part of pilot studies and this is ONLY because of my samples that I have and how knowledgeable I am about the breed. Gluck is relying on it for some really big applications in research. I just can't say anything. That is why I haven't said anything someone would get their hopes up if the pilot project doesn't find anything. 

Remember we are not talking about humans we are talking about horses, pets, and the genetic diseases we see in them. Horses are something of a side note in the overall picture of genetic research since mice and other lab animals are much more suited for genetic research that can influence the work done in humans. And in the overall picture of horse genetic research, we as the Miniature breed are considered a fly on the butt of the horse in most (but not all) research labs that work in equine genetics only. 

So, I really think some Miniature people think we as a breed have a bigger influence than we really do. We do not have any million-dollar races, we do not have any million-dollar titles. We do not have even any 50,000-dollar awards, ie futurity or performance related awards, but there many other money driven breeds that exist that do, and they are the ones getting looked at by research labs much more than us. 

John  

 
More Articles - Environmental Deformities Nov. 19 2007 
Question 
You said in your reply to my original question (Environmental Birth Defects That Mimic Dwarfism???) that you would be interested in seeing more articles. I was able to find a few more papers that gave some details about environmental deformities. I have not had a foal that I think had 'environmental deformities' vs 'dwarfism', so my interest is in knowing how to tell the differences should I have a foal with dwarf/dwarf-like feature. If it is environmental, then I would approach the problem from a completely different angle than if I was dealing with the dwarf gene. 

Just a note, the article you quoted in answer to my initial question, is the ONLY one that I have found that talks about "mandibular brachygnathia" (parrot mouth/over-bite) being associated with the environmental syndromes. ALL of the other references talk about "mandibular prognathism" which is the undershot jaw/underbite which is a common trait in a dwarf foal. 

The articles also talk about domed heads and hydrocephalus. Hydrocephalus can cause a domed head. Here are definitions of hydrocephalus in cattle, the first two sound very much like a description of a dwarf head... 

hydrocephalus - There are three forms that occur in cattle: in one there is gross distention of the cranium with normal facial bones; in the second there is a similar enlargement of the cranium with an accompanying achondroplastic dishing of the face and foreshortening of the maxilla and a shortening of the limb bones these are the classical bulldog calves; in the third the cranium is normal in size but there is internal hydrocephalus and the calves are blind and imbecile. 

Nearly all the articles talk about deformed legs and joints and contracted tendons. Several of the dwarves that I have seen have had twisted limbs and contracted joints. The articles don't really mention disproportionality of the limbs as a symptom, just deformity. But, from your descriptions of the dwarf types, it is only in type 2 dwarves that you would expect to see disproportionate legs manifested by shortened forelimbs. So, lack of disproportion, doesn't rule out the environmental leg deformities mimicking dwarf characteristics, as not all types of dwarf have disproportionate legs at birth, some dwarves only have the deformed legs. 

I guess from what I have been reading, I am still not seeing how a breeder can get a clear- cut idea of whether a foal with deformities that LOOK similar to those caused by genetic dwarfism is suffering from dwarfism or environmentally caused birth defects. What specifically will a person see that is different? Unfortunately, there were basically no photos to go with the articles, so it is hard to picture the differences that exist, or if the differences are indeed easy to tell apart. I am hoping that you can give a good description of how the two are different. 

Anyway, here are the additional articles that I found. I will give the website address and then a short excerpt that mentions the specific deformities that seem to be in common between environmental deformities and true genetic dwarfism 

https://www.horseandhound.co.uk/horse-care/vet-advice/problems-of-the-equine-thyroid-71361 

Signs of Hypothyroidism in foals 

Weak at birth and often not full-term 

Poor sucking and righting reflexes 

Lack of coordination 

hypothermia 

Long coat 

Respiratory problems 

Stunted growth 

Developmental bone and muscle problems, such as undershot jaw and bent legs 

Early death 

http://www.vet-med.wsu.edu/depts-vth/EquineNews 

Hypothyroidism in Foals Tissues were received from a nine day-old non-viable Quarter horse foal that died following a short illness. On microscopic examination, sever goiter (thyroid hyperplasia) was diagnosed on section of thyroid tissue and, within the heart muscle, there were areas of acute degeneration and mineralization consistent with a nutritional cardiomyopathy. No leg or joint abnormalities were observed, although madibular prognathism (lengthening of the bottom jaw or mandible relative to the upper jaw), was observed. 

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=548628 

Thyroid hyperplasia and musculoskeletal deformity (TH-MSD), a syndrome of neonatal foals well recognized in western Canada (4), where it is considered an important cause of foal mortality and reproductive loss (5), has not been commonly reported in eastern Canada. The musculoskeletal deformities observed include flexural deformities of the limbs, muscular weakness, mandibular prognathism, and doming of the head. There was pronounced mandibular prognathism* (*note - this is an underbite) 

http://www.westernhorsereview.com/reader/ask_expert/nutrition.html 

It is characterized by foals being born weak or dead with contracted tendons and a deformed jaw (elongated lower or shortened upper) 
 
The following Q and A was published in Western Horse Review Feb. 2007 

-------------------------------- 

Q. A friend of mine just lost a foal; it was still born and had a palate deformity. Her veterinarian asked her if the mare had been turned out on green feed in the fall. Why would she have asked that question? I am interested because my own horses are turned onto barley fields after harvest. 

A. Mike Scott, a veterinarian with Moore and Company, Calgary Alberta, provided his insights on this subject: 

Your question doesn't have an easy answer. Your friend's veterinarian was likely curious about the mare's exposure to green feed because of an ongoing study being conducted by the Western College of Veterinary Medicine into something called Congenital Hypothyroidism and Dysmaturity Syndrome. I happened to be one of the researchers involved in looking into this Syndrome in 1994-95. The Syndrome, which is specific to western Canada, has been recognized since the late '70s. It is characterized by foals being born weak or dead with contracted tendons and a deformed jaw (elongated lower or shortened upper) - both signs of skeletal immaturity that are a result of malformation of the thyroid gland or lack of thyroid function. An extensive survey conducted by the WCVM of western Canadian horse breeders into the management of broodmares and breeding herds led researchers to conclude that the common denominator in the occurrence of CHDS was the feeding of green feed to mares during pregnancy. Green feed, if cut during a period when the crop is stressed by frost or drought, can have a high nitrate content. Consumption of water with high nitrate content in third world countries has been shown to result in thyroid diseases in people; it seemed likely that high nitrate in green feed could cause similar thyroid problems in horses. However, further testing involving feeding pregnant mares green feed with high nitrate content failed to prove the theory. Still, it is possible that a relationship exists between a mare eating green feed and the type of foaling problem experienced by your friend. Research into CHDS is still being done at the WCVM, spearheaded by Andy Allen. So, while there is no definite conclusion that can be drawn about why your friend lost her foal, her vet's interest in a green feed connection probably relates to this study. 

----------------------------------- 

http://animalag.wsu.edu/newsletters/CWAATQrtrlyNwsltrfeb07.pdf  and the birth of foals that commonly have mandibular prognathism, the fine skin and soft silky haircoat of premature foals even though they are over term, incomplete ossification of the cuboidal bones of the limbs, flexural deformities of the forelimbs, and commonly ruptured digital extensors. Some have hydrocephalus and some patent urachus. 
R3 
Julie Miller 
R3 Minis – Fletcher Oklahoma 
 
Answer 
I get the feeling you really feel that the dwarfism we have in the Miniatures is caused solely on hypothyroidism due to environmental causes, like nitrate levels or iodine. I really don't think whatever I say will change that, so all I will do is comment on my opinion of the article you presented anything else I say will not be of any consequence to your opinion 

As for hydrocephalus it is caused by water on the brain. Of course, it will make a head domed, but again what does that have to do with an inherited disease that has a consistent type all over the world. Some dwarfisms in humans have hydrocephalic characteristics, so what, I think you are getting confused as to what I was commenting about from the original thread. Oh, and bulldog calves from dexter cattle have a test for that dwarfism, and it is inherited as an autosomal recessive with carriers that are smaller than normal non-carriers, with carriers showing disproportionate legs to body but do not show the disease which is lethal in homozygous form. 

A quote from your first article listed 

"In the past, the thyroid gland has been blamed for more than its fair share of problems. But the latest technology and improved blood tests indicate that true thyroid disease in horses is quite rare, and ensuring the right levels of iodine in your horse's diet can prevent most problems." 

The second would not open 

But from what I could read, I guess you are getting confused with hypothyroidism and dwarfism, since there was no dwarf disproportionate leg or body characteristics. There are many diseases that have one or two symptomatic characteristics or more with dwarfism, again one horse, not a dozen or so or hundreds all over the world in various environments 

About the third article 

This article was on 1 (0NE) foal not even a dozen or even 100, but one foal. I can't tell you how many things or various degrees of exposure can cause congenital malformations in only one animal in only one species, there are probably millions of examples. In other words, there are billions of things randomly that can happen all over the world, and there are things that can happen that look like an inherited disease that occurs by chance and not due to a dwarf gene, this foal looks like one of those examples. 

A quote from your third article listed 

"The etiology of this disease is highly debated. Poor nutritional management of the mare appears to be the most likely cause in most cases. Pregnant mares fed diets that contain high levels of nitrate or that are iodine deficient have been associated with an increased risk of producing an affected foal (4). Also, the presence of fungal toxins in the diet of pregnant mares has been associated with congenital thyroid hypoplasia (9). 

In this case, the mare was fed a diet of moderate quality hay and oats throughout gestation, with no mineral supplementation or access to pasture. The mare may have been iodine deficient due to the lack of mineral supplementation, the hay may have contained nitrate, or both. Nitrate is more likely to be present in green feed (immature cereal crops). Forage grown under stressed conditions, such as dry weather, has an increased probability of containing nitrate (10). The summer of 2001 was very dry in southwestern Ontario, which may have resulted in an increased nitrate level in some Ontario forages. The forage grown during the summer of 2001 would have been fed during the latter two-thirds of gestation to mares that were bred late in the season (May and June 2001). The equine fetal thyroid gland becomes active by the 4th or 5th mo of gestation (2) and may be most susceptible to insult from poor nutritional conditions in the early to middle part of gestation. 

The dry summer of 2001, combined with lack of mineral supplementation, may have predisposed some late-bred mares in Ontario to produce hypothyroid offspring in the spring and summer of 2002. However, it is important to note that there are other potential sources of nitrate, including contaminated drinking water and irrigated pastures. Further investigations should be conducted regarding the prevalence and etiology of TH-MSD in foals in Ontario to increase awareness of this disease." 

I don't see how this can explain all of the dwarf Miniatures all over the World in different environments. 

As to answer your fourth article, if he was one of the researchers that published with Dr. Allen then they should talk because DR. Allen's work is getting used as reference with one of the symptoms as "mandibular brachygnathia" that is seen. So, there are either typos which is likely and or more likely variable characteristics of both parrot and monkey mouthed seen which would not surprise me in the least, since they explain how the hypothyroidism is affecting the growth of the head. 

A quote below from the fourth says how regional it was. 

"I happened to be one of the researchers involved in looking into this Syndrome in 1994-95. The Syndrome, which is specific to western Canada, has been recognized since the late '70s." 

In your fifth article all I found was this, it was not what you quoted but I think you are referring to the same thing. Again, what does this have to do with dwarfs seen in Australia, New Zealand, Europe or US that have not been exposed to the mustard plant, or for that matter, since these foals have to be put down right away or die early, how does that explain adult dwarfs that are five or ten years old. 
 

Congenital Hypothyroid Dysmaturity Syndrome 

This syndrome with a whopper of a name applies only to foals. An affected mare may have an abnormally long pregnancy, abort or give birth to an abnormal foal. Affected foals often have an abnormal jaw, immature hair coat, fine skin, poorly-calcified hock and knee bones, abnormal curvatures of the front legs, congenitally-ruptured tendons and other abnormalities. Most effected foals die or need to be euthanized. The cause of this disease is believed to be the ingestion of late winter/early spring weeds by mares during late pregnancy. Mustards and other members of the Brassica family are believed to be the main culprits. Chemical compounds in these plants seem to have goitrogenic (thyroid-stimulating) effects, even though the foals are not born with goiters. The risk factor is present in both fresh and dried plants, so weedy hay is also, a concern. Nitrates may also be involved in this syndrome, but that is under investigation. Horse owners should feed weed-free hay to pregnant horses and keep these animals out of weedy areas until after foaling. Mares that have foaled one affected foal are at higher risk to do so again, perhaps because of a behavioral component that involves preferential eating of the toxic weeds. 

 I really think I have beat a dead horse for the last time. 

 John  

Question on breathing issues as well as Downs syndrome in horses/dwarves?? Nov. 19 2007 
 
Question 
Hi John, 

As most know I did have a dwarf born at our farm .. she was not only a dwarf but born very premature so her lasting as long as she did was nothing short of a miracle. 

We lost her and it happened pretty quick she was just over a year old and had some raspy breathing one morning. We did have a virus running thru here so I thought that was it but within a couple of hours she could barely breath. We got to vet where they pulled blood and it was literally almost black.. they x-rayed her and found (I will try to get this right) that her soft palate basically due to the shape of her head grew to the point that it was covering her trachea and was choking her. We had to put her down. 

I know a couple others on the forum who have had dwarfs would write that they were having breathing issues that seemed to come on suddenly and had to be put down for the same thing. 

Is this something that is a more common then not cause of death in dwarves I have also found and I am sure some are going to misunderstand me but the dwarves that I have known in person had a much different personality then other horses the only way I can describe it but they are almost like children with downs syndrome in personality- is this a normal or something that you have found to be consistent in dwarfs or is there such a thing as a horse form of downs syndrome that could be a common link in dwarves. 
Lisa-Ruff N Tuff Minis_* 
Lisa Andrade 
Ruff N Tuff Miniature Horses –Nampa Idaho 

Answer 
Lisa, 
Something like that is seen in human dwarfs with certain types of dwarfism. ACH has the Magnum Foramen problem in humans, which causes breathing problems in the human dwarfs and can cause death if not surgically corrected. 

This breathing problem I have seen as a common characteristic in certain Mini dwarf types. Dwarf horses do have personalities that sometimes are unusual but I think a lot of that stems from the way they are cared for, by meaning having a lot of human only interaction, therefore learning body language skills of humans, etc versus horses because they are not usually with alot of horses. I will say I have seen some dwarfs that were mostly kept with other small minis and did not have that much human contact and about the same as the other normal horses and the dwarf was very horse not human in its actions and personality. 

As for Downs Syndrome, that in humans is caused by trisomy 21 of the human 21 chromosome. The 21 chromosomes of the horse do not carry the same information and I do not know of a specific trisomy 21 in the horse that was documented as even alive or functional, I would have to look that up. Horses have a different number of chromosomes than the human with the genes being on different chromosomes you are dealing with apples and oranges. 

John  

Outcrossing on Shetlands Nov. 26 2007 
Question 
Hi John, 
Thanks so much for answering questions! This is all very enlightening. I'm not sure if I can word this correctly hopefully it's not too confusing. I found it interesting in several of your posts that you had said that you had never seen dwarfism in purebred Shetlands (and other pony breeds you mentioned). By outcrossing more with Shetlands would this gradually reduce the carriers produced since that gene is not coming from one of the two parents each time? If you were to heavily out cross over several generations would you likely eliminate the dwarf gene in that line all together? 

If so this "fad" (as many like to call it) of ASPC/AMHR horses could only be GOOD for our, lack of better words, "breed". 
Thanks,  
Hillary 
Boinky Sport Horses, Miniatures - Berea, KY

Answer 
By introducing horses (ponies of any breed) with genetics that are not, you can gradually decrease the percentage of resulting carriers, but it would take quite some time. For one you do not know which foals from the crosses are non-carriers and which are carriers, only breding and getting a dwarf would distinguish that. Using the ponies as outcrosses does not solve the problem short term or even long term genetically for well conformed desired horses that are still carriers of the recessive gene, because those individuals would still carry those genes on to their offspring and later generations. What was done decades ago in the Hereford and Angus cattle breeds was the carriers of the recessive dwarf gene were slaughtered as soon as they produced a dwarf. That very quickly removed a large portion of the dwarf gene carriers. Thereby it was pretty much eradicated by slaughter and got meat market money for the carriers rather than trying to find a common physical trait and solely basing the carriers on that trait, (this was before animal genetic research testing was common). We in the horse industry dont have that option at all. 

So, to answer your question as easy as possible, adding pony breeds to the gene pool will help dilute the number of carriers within our "breed" over the long term and make the dwarf genes less common within the gene pool therefore causing less dwarfs to be born. However, it will not eradicate the dwarf genes from the total gene pool within our "breed". 

John  

Bloodlines Nov. 30 2007 
Question 

What bloodlines should we be concerned about for the dwarfs. Do any of the Fallabella bloodlines or the popular names like Bond or Brewer have any dwarfs in them. I have a lot of Bond and Komoko and I am concerned about that because so many of my horses seem to be related to one another in a way. I just am hopeful that someday we can have a list of the bloodlines that have dwarfs in them just so we can know.  

Shadowsmystictopaz 
Sue & Dave Weinert 
Diamond W Ranch – California 
Andrea Weinert idea maker 

Answer 
Your question was asked earlier in the forum when it started. I will say again, I cannot give out pedigree info that I am using in my research. It would be me publicly saying "such and such" stallion or "such and such " farm has produced a certain number of dwarfs and without scientific proof it could ruin a stallion or bloodline or farm just on here say. I don't think people would appreciate it, especially if it was your stallion or breeding program. 

In general, I will say like I said in the other answer, these dwarfisms are extremely intertwined within the WHOLE breeding population. My dwarf samples have pedigrees and backgrounds of every well-known pedigree in the world. It is not wise to get hung up on "bloodlines"; many carriers have extensive old bloodlines that are intertwined, and the same is so for the non-carriers, you will not know which are carriers and which are not until you have a dwarf. 

We are NEVER going to know the original culprits, so get over that thought, go from here and learn what actual horses have produced dwarfs. 

John  

Non-dwarf question Nov. 30 2007 
Question 
I know it is a non-dwarf question, and maybe you cannot answer it, but I have always wondered what the connection is between coat color and the gi tract in horses? To clarify, why do lethal white foals die due to issues in the intestine? Are these gene's loci on the same chromosome? 

I've just always wondered. 

ckmini 

 CK Miniatures and CK Performance Horses - Montana 

Answer  
Here is the NCBI link that briefly explains the answer to your question, and gives links to other research papers that are about the disease and the color link. 

https://www.ncbi.nlm.nih.gov/sites/entrez?db=omia&cmd=search&term=lethal%20white%20overo       2012 UPDATE BY ADMIN The long-provided link now goes to a not found page. Please go to: https://www.ncbi.nlm.nih.gov/   and in the provided search box type in: “ lethal white overo “  for several wonderful articles on this topic. 

If it does not go to NCBI let me know. 

The mutation in the gene that causes the lack of coat color migration (i.e. pigmentation) is also responsible for nerve cell development of the neural crest stem cells. It is a little complicated to try and explain all of this in embryonic development terms without using diagrams and a lot of typing so you might want to google embryo development stages and you will probably be able to find really good pics. 

John  

So, what can we do? Nov. 30 2007 
Question 
So, what can we, as breeders, do now, in your opinion and until we have more information or testing, to try and breed better horses and lessen the chance of dwarfism?  

MiLo Minis 
Lori Rafter 
Maple Mountain Miniatures - Ontario Canada 

Answer 
Learn all you can about good horse conformation, from large horse books. Genetics and breeding reference books. Online book stores look for equine breeding management or genetics. There are a lot out there. Then pay attention to as much as possible the dwarfs out there you se, either in person, or on the internet, try to find out as much as possible through first hand info on pedigrees, not, someone heard that such and such stallion had a dwarf or a bunch of dwarfs, when you see them find out pedigree info if possible. Remember what I wrote about how pervasive these dwarfisms are in the breed. Do not get hung up on a certain head type or other individual traits that most likely are not the recessive gene having expressivity. There are a lot of non-desired traits within our breed. We are not a "true" breeding "breed", we can get anything under the rainbow. 

John  

 
Bond Tiny Tim? Nov. 30 2007 
Question 
We all know that Bond Tiny Tim was a dwarf. How far back in the pedigree does he have to be before you don't worry so much? I have a Bond Dynamo son out of an Orion daughter and he has never produced a dwarf for me and can only assume he didn't for his previous owner. 

Thank You, 
Robin1 
Robin  
Phoenix, Arizona 

Answer 
It does not matter anymore. Can you stand up and say 100% that every bit of all of your horse's pedigrees are true and accurate to the founding generations???, if they even go back seven or eight generations. There were many things done years ago, I trust newer pedigrees with DNA and PQ on them that they are accurate for the recent generations but I really do not take much from old pedigrees in the sense that they are all 100% accurate. I use that as "general" info when I do pedigree work on my samples as possible ties but I cannot use that as true and accurate info to base any opinions on. Again, individual horses that are non-carriers can easily exist from pedigrees of known dwarfs. 25% of all the foals born to two carriers of a specific type will be genetically normal and never produce a dwarf of the same type, because that 25% did not inherit the defective gene from either parent. 

John  

What about the dwarfs that are born? Nov. 30 2007 
Question 
This might be a dumb question? 
With your research, is there anything that might help the dwarfs grow after birthing? 
Just wondering?  

Reble 
Mary Kavelman 
Kavelbel Miniatures - Ontario Canada 
 

Answer 
No. 

There is nothing that humans can do to help the human dwarfs grow to normal size except surgery on a select few bones in a select few types of dwarfism in humans, (ie ACH dwarfism and the surgery to lengthen the long bones of the legs and arms). There is nothing that can help the horses, I really do not think Science or anyone's bank account is interested in that expensive and experimental endeavor with the horses either. 

The diseases cause the bones to grow abnormally or not develop at all in to normal functional bones. Therefore, you can't change the genes and how they have been mutated and are encoded to produce proteins that are abnormal. Gene therapy is something that in other diseases is a sci -fi endeavor right now. I do not know if it will ever be possible for that in human dwarfisms let alone horses. 

John  

One Final Question from me, Nov. 30 2007 
Question 
I also have one final question that I have often wondered about. Have you at all found during your studies that horses with a very high tailset will often throw dwarf foals? I guess what I am asking, is would/could or has this proven it can be a sign of (carrying) dwarfism? I have heard of various dwarf signs to watch for, but had not heard of that one, and it has just been a personal observation of mine where I have often seen dwarfs, and one parent had the extremely high tailset, so always wondered if perhaps there was something more to it, as in it may be an expression of a horse carrying the dwarfism gene? Thank you.  

Mona 
Mona Stone 
Last Chance Miniatures - Ontario, Canada 

Answer 
Mona,  

Sorry but no. You are seeing way more into this than is there with regards to specific conformational characteristics. That would be similar to me saying that many small eared horses that I have seen have produced dwarfs. There is no way to prove that whatsoever. I do not know of a normal conformational characteristic that has anything close to being associated with dwarfism. A high tail set or low tail set, it doesn't matter each one could be a carrier or not be a carrier. I can show you pictures of both, carriers or non that have both types of tail sets and every degree in between. 

As a side note, think about the question you asked. If only one parent of a dwarf had a high tail set and the other did not, why would you associate dwarfism and a high tail set. BOTH parents would need to have a high tail set to be showing signs that it is associated because BOTH parents contribute a recessive diseased gene to the dwarf. If only one parent, you say, has a high tail set of two parents that have had a dwarf, then that alone blows your theory out of the water. 

John 

question on signs and pedigree - Nov. 30 2007 
Question 

May I send you links to a mare and two stallions with pictures and pedigrees? One combination produced a dwarf and the other did not. I can't post here who they are because I don't own the stallions. 

Thanks 
yankee_minis 
Tracy Palmer 
Bito-O-Blue Miniature Horses - Maine 

Answer  
Yes just email by PM or email me to arionmgmt@aol.com.  

John