I might finally get it
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Re: I might finally get it
It was a highly expressed tobiano with the white going all the way up the legs and over the back with the tailhead white as well so you could see tobi pretty distinctly from behind.
Night blindness is in any homozygous Lp horse so any breed that carries the appy pattern (minis, Knabstrups, etc) can be night blind.
Re: I might finally get it
[quote="Jenks"][quote="rabbitsfizz"]But, night blindness is [i]only[/i] in H/Z Appy?
I mean, sorry, not expressing this well, is night blindness only attached to appy, or can it exhibit in non appy animals?[/quote]
I thought it was Lp.[/quote]
Yes, it is H/Z LP (appy). I have never heard of other patterns (non LP) being night blind...yet.
Re: I might finally get it
There have been a few published cases of CSNB (a thoroughbred and a paso fino if I recall correctly) in non-appy horses, but they were linked to other eye problems and I believe one had to be put down for other congenital defects. The CSNB that is linked to the TRPM1 gene is only found in horses with Lp.
Re: I might finally get it
From my senior thesis paper:
Horses that are homozygous for the leopard complex gene, Lp/Lp, are also affected by a genetic condition known as Congenital Stationary Night Blindness (CSNB).24,23 This condition is characterized by horses that have normal pupillary light response, menace reflex and ophthalmologic exam, but have reduced to absent visibility in dim light.25,23 This condition has been further diagnosed using electroretinography.26,23,25 In a horse affected with CNSB, the ERG shows a depolarizing a-wave and absent b-wave in dark-adapted horses (figure 13). Rod photoreceptors are most sensitive under scotopic* conditions and should signal a depolarization of ON retinal bipolar cells when they become stimulated, which then results in the b-wave present on a normal ERG.27,23-25 When investigating the cause of CSNB and the appaloosa pattern, researchers found that cells of horses affected with CSNB had differential expression of the gene TRPM1*.24,26 TRPM1 is thought to play a role in neural transmission within the retina by reducing depolarization by changing the free Ca++ in the retinal ON bipolar cells.28,26,27 There is down-regulation of TRPM1 in heterozygous Lp appaloosas, but less significantly than in homozygotes.24 How the TRPM1 mutation results in the spotting pattern seen in appaloosa patterned horses is still unknown, but researchers hypothesize that it may affect the signaling pathway of the melanocytes.24,26
As long as an appaloosa patterned horse has at least a small blanket of white on their rump, identifying which are affected by CSNB is as simple as determining whether or not there are spots present in the white area of the blanket. The horses that have spots in their white areas, such as spotted blanket or leopard spotted, are heterozygous for Lp and not affected by CSNB.22,26 Those that have no spots in their white areas, including snowcaps and fewspots, will be affected by CSNB. While this is simple in Lp carrier horses with obvious white patterns, if a horse does not have expression of a white pattern, then it can be difficult to determine zygosity. These non-white horses are called ‘characteristics only’ as they express Lp in their mottled skin, white sclera and striped hooves, which are characteristic of all Lp carrier horses. With the association between Lp and CSNB being established, ‘characteristics only’ horses can be tested for homozygosity by testing their vision in scotopic conditions (figure 14).24 Owners of CSNB horses need to be educated on safe practices when dealing with horses that are unable to see at night or in dark situations. They need a safe environment at night so they are not injured by objects they cannot see such as unsafe fencing or obstacles within their paddocks. CSNB horses should be approached cautiously in dark situations while giving them plenty of warning of an approach and allowing them adequate time to adjust to darker areas. Unless severely affected, CSNB horses can be ridden safely in most areas with some lighting, but dark arena and night time riding should be done with extreme caution. Breeding two homozygous appaloosas will always produce a horse with CSNB. Breeding a homozygote to a heterozygote will produce a CSNB horse 50% of the time. Breeding two heterozygotes together will produce a CSNB horse 25% of the time. To prevent a CSNB horse, homozygote or heterozygote appaloosas can be bred to a solid (non-Lp) horses.14,22,23
Re: I might finally get it
I have two homozygous LP horses (LP/LP). They don't have a problem getting around at night. Their night blindness doesn't affect them at all. They have normall eyesight durring the day. They have no pain etc. My friend has a H/Z LP roan mare. She has extreme roaning but has no dense white. She is also night blind. Why would we want try to avoid breeding for LP/LP?
Re: I might finally get it
Well, even if the condition can be managed, I would not consider it altogether ethical to deliberately breed for a genetic condition that adversely affects the horse. It's like breeding a known conformation fault forward, bad legs, bad feet, etc. Even if the horse remains useful and pain free, no breeder worth their salt would want to perpetuate a fault.
Re: I might finally get it
[quote="Maigray"]Well, even if the condition can be managed, I would not consider it altogether ethical to deliberately breed for a genetic condition that adversely affects the horse. It's like breeding a known conformation fault forward, bad legs, bad feet, etc. Even if the horse remains useful and pain free, no breeder worth their salt would want to perpetuate a fault.[/quote]
i totally agree Maigray it isn't ethical and i will tell me friend who is new to appies to watch out for it. ;)
Re: I might finally get it
[quote="lipigirl"][quote="Maigray"]Well, even if the condition can be managed, I would not consider it altogether ethical to deliberately breed for a genetic condition that adversely affects the horse. It's like breeding a known conformation fault forward, bad legs, bad feet, etc. Even if the horse remains useful and pain free, no breeder worth their salt would want to perpetuate a fault.[/quote]
i totally agree Maigray it isn't ethical and i will tell me friend who is new to appies to watch out for it. ;)[/quote]
I also totally agree....If it was considered a fault. It isn't.
Re: I might finally get it
But it's a fault with their vision, isn't it? If they can't see well at night and some horses are affected more and some less, but no one wants a horse whose vision is compromised in any way. It's like deliberately breeding a defective animal, you are saddling them with a handicap that affects their usability, their temperment, their physical ability. Plus, the owner will incur costs. I know lots of breeders make compromises and everyone has their own personal line - for me, this is one of them. Just for a color, something so unimportant in the larger scheme of things and so easy to work around. You don't even have to give up the color, really, just breed around it. If a breeder were willing to use a homozygous animal to only produce heterozygotes and they took responsibility for it, I suppose that could be done, but still..
Edited to add - Appies are not my specialty, but has it been absolutely proven all homozygotes will be night blind? I was aware it was a problem, and I was sort of peripherally aware this was believed to be true, but has it truly been proven? This would be very hard on breeders with Lp in their herd, so I understand some are willing to live with it sans proof, at least.
Re: I might finally get it
I don't personally believe that night blindness adversely affects the condition of the horse. Most owners aren't even aware that their horses are night blind. I currently own four LP/LP horses, and it hasn't caused any problems whatsoever. Their usability, their temperament, and their physical ability are completely unaffected. It's not a condition that needs to be treated (unlike uveitis) so there are no costs incurred. The horses are born that way, it's all they've ever known, and they're very well adapted to the condition. This is nothing new -- LP/LP horses have been night blind since the beginning of the mutation, and they still exist to this day.
As far as I know, all LP/LP horses are night blind. I believe only 10 horses were used in the study, but they seemed to feel that was enough. No HZ roans were used, since it's very difficult to distinguish LP/LP roans from LP/lp roans.
Other horses [i]can[/i] be night blind. I used to own a non-LP mare that was definitely night blind, but whether is was CSNB or something else, I couldn't say.
Re: I might finally get it
All LP/LP horses are night blind...from all I've read. It isn't a problem at all.
My horses are on 250 acre pastures 365 days a year. There are deep woods traveling along a seasonal creek with a deep creek bank along most of it. Deep meaning from 15 to sometimes 20ft deep. After a rainstorm, the creek is really more of a river. The creek splits the property in half, but not flowing in a straight line.
Unfortunately, we have several different wild predators. Cougars, wild dogs, wild hogs (these are extreme pests) & now it seems a few black bear have arrived....(((oh joy)))
My horses don't have a problem finding their way through the woods or around the creek. If a cat is in the area, all of the horses stay in the open, close to the house. The night blind horses are just as capable as the others. I never would have known they were night blind had I not read the articles & tested them at night, knowing they were H/Z. Everyone I know with LP/LP horses feel the same way. It isn't an issue.
I have a friend who sometimes rides his snowcap stallion at night but knows to take the trail if riding after dark. His horse has no problem if he knows his surroundings. He rides this stallion endurance & has had no problems because of eyesight. Here they are.
[img]http://i39.photobucket.com/albums/e156/…]
Re: I might finally get it
If being night blind was a handicap, this fewspot wouldn't be the best trail horse to set foot in the mountains! We quite literally trust our horses with our lives; that's [i]not[/i] an exaggeration. This is a horse that will bring 'em back alive!
And some people think horses like this shouldn't even exist?! :rofl
Re: I might finally get it
[quote="Arock"]
Unfortunately, we have several different wild predators. Cougars, wild dogs, wild hogs (these are extreme pests) & now it seems a few black bear have arrived....(((oh joy)))
[/quote]
There are black bears here???! :shock: I've heard about the cougar but I haven't seen it yet.
Re: I might finally get it
[quote="Maigray"]
Edited to add - Appies are not my specialty, but has it been absolutely proven all homozygotes will be night blind? I was aware it was a problem, and I was sort of peripherally aware this was believed to be true, but has it truly been proven? This would be very hard on breeders with Lp in their herd, so I understand some are willing to live with it sans proof, at least.[/quote]
There are those who say that the original test group, especially in light of no test for Lp, was too small (30 horses--10 believed to be LpLp by phenotype and I believe progeny stats; 10 Lplp and 10 believed to be lplp based on phenotype). There are many like Arock, who have owned LpLps, and have noticed absolutely nothing different in how their horses act in day or night. There are those who have seen obvious differences in behaviour between their horses being in bright light and going into dark.
The thing is, CSNB in apps is there from birth, and the CSNB horse is used to those conditions, and handles them with no stress, at least in familiar surrounds. We've one, probably 2 LpLps in our current herd, and I have to say we've had less problems with them than other people who have Lplp horses. They also seem to be the least likely to get bumps and bruises. /shrug/ To do totally away with CSNB in apps, one would have to make sure to never breed an Lplp to another Lplp, and well, that's going to do away with the breed, sooner or later.
Diane
Re: I might finally get it
[quote]To do totally away with CSNB in apps, one would have to make sure to never breed an Lplp to another Lplp, and well, that's going to do away with the breed, sooner or later.
[/quote]
That is exactly what happend with LP in several breeds...mine included. Fewspots & snowcaps were gelded because it was thought they weren't pretty like the spotted horses....why breed them. The large spotted blankets were gelded to make flashy riding horses. Nose to toes leopards were bought up to help form the POA. It wasn't long before a horse with Lp at all was rare.
Re: I might finally get it
I have known a suspected Fewspot who was hopeless at night, and still is. Luckily he is a Mini so it is easy to manage.
I agree in principle that this is a fault, and should be treated as such.
If it does turn out that all Fewspots are affected then it would be better not to breed them intentionally.
I remember a few years back, people thought it was totally OK to breed LWO X LWO because the risk of getting a Lethal White foal was acceptable.
Nowadays, thank goodness, although there are still people who do think this, they are becoming a minority.
If there is a way round this problem, it should be found, and taken, but saying it is not a fault, and not a problem, does not help.
It quite obviously[i] is[/i] a fault.
How big a one remains to be seen!
Re: I might finally get it
There is a huge difference between running the risk of producing a foal that won't live more than a week and running the risk of producing a foal that can't see in nearly black-out conditions. Might as well do away with Lp breeds totally, since they are more prone to uveitis courtesy of the mottled/pink skin around the eyes, which is a common characteristic, and since uveitis can lead to considerable medical 'damage' to a horse's eye.
Diane
Re: I might finally get it
What I have been telling veterinarians and a few clients is that it is something that owners need to be made aware of (particularly for prepurchase exams), but not that it is a big deal if the horse is compensating well (as most do). Mostly I just warn them about moving them to new places in the dark and to be aware of it if riding/working with the horse at night. As I had an LpLp that I would take on night rides and never had a problem with, I know what they are like and I never had a problem with mine.
Re: I might finally get it
That's all well and good, yours obviously compensated well, and, of course, had a rider who was aware of possible problems.
What I do not understand is saying it is not a fault.
It is patently obvious that it [i]is[/i] a fault.
Not an "end of the world" one, and one that has to be taken horse by horse.
It is quite possible that people who are knowledgeable will take it in their stride.
BUT, if this pattern is deliberately bred for, and it is, then the breeders have to be prepared to take care of the affected animals that end up as riding geldings, as opposed to fancy studs.
They are the ones that are possibly going to suffer.
Accepting that it is a fault, with all the possible problems associated with it, is the first step, I would have thought.
Re: I might finally get it
[quote="Monsterpony"]What I have been telling veterinarians and a few clients is that it is something that owners need to be made aware of (particularly for prepurchase exams), but not that it is a big deal if the horse is compensating well (as most do). Mostly I just warn them about moving them to new places in the dark and to be aware of it if riding/working with the horse at night. As I had an LpLp that I would take on night rides and never had a problem with, I know what they are like and I never had a problem with mine.[/quote]
LpLp are not not night blind.
I am pretty much night blind. I don't go anywhere at night without a flashlight or lantern etc. I get along pretty well. I'm very happy to be breathing. I think I compensate well....for the most part. My mother was night blind also. I'm certainly glad she decided to "breed"... :rofl
I would never have known that my LPLP horses were night blind had I not read the paper on it. They never showed any signs...none of them do. AppyLady said, that they rely on their fewspot gelding entirely to keep them safe in the mountains. I don't think many people can say that about their horses... sighted or not. I know where they ride & it's not a manicured trail....at all! Horses need to be sure footed & steady headed in those mountains. Accidents happen up their all the time. LPLP horses see perfectly normal in daylight.
Re: I might finally get it
That's awesome! I should pay more attention to colors on horses I trim, I just kind of get in hoof centric zone, and taking in the shape and size of the horse and just see the general color without thinking about it :? :oops:
And lol @ predicting the face white by the rump marking, you could start saying what your thinking out loud and amaze everyone :P you might sound like my dad who will tell you the major plot twists in a movie or show 5 minutes in and be right 90% :lol: (I usually don't like spoilers but it so funny when he's always right I can't even be annoyed lol)