Minimor
Well-Known Member
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!)
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!)
