Like in humans, does it lead to genetic defects in animal species ??
If not why ??
Well, it DOES lead to genetic defects sometimes. Unlike with humans, though, animals with birth defects are generally culled.
Secondly, if the animal is inbred on purpose by a breeder, then there’s generally something in the line that the breeder wants to strengthen. Again, though, when the result turns out to be not so much what the breeder expected, they can cull the animal.
Yes - of course it does. That’s why pure bred pedigree dogs have high incidences of conditions like hip dysplasia. Good breeders cull - or at least don’t breed from - lines that have the genetic disorder.
According to my vet, in rabbits, inbreeding has led to increased occurrences of reproductive cancers, often necessitating getting them spayed or neutered to prevent disease.
I bred persian cats at one time. The owner of the male I used didn’t check the linage and I ended up with a whole litter with cleft palates and cleft lips. I had to put them all to sleep, since they couldn’t nurse. 
It does lead to genetic defects of all kinds in horses. There’s a large number of diseases that probably wouldn’t be as prevalent as they are were it not for the huge amount of inbreeding. Best example I can think of is the horror of HYPP [Hyperkalemic Periodic Paralysis], a/k/a Impressive Disease Wiki entry .
It’s a big subject of controversy among Quarter Horse breeders and owners, and only recently has the American Quarter Horse Association done anything really worth talking about in requiring ANY horse out of that bloodline to be tested for HYPP, and in the last year or so, they’re not registering any horse that shows up double positive for HYPP. It’s really sad to see a horse stricken by this but thankfully there’s treatments and management programs that help them.
Darn it, I was going to mention Impressive! 
It also happens on other animals, like dairy cows.
Darn it, I was going to mention Impressive! 
And I timed out on the edit window…
It also happens with other diseases, like Bovine Leukocyte Adhesion Disease in dairy cows, and SCID in Arabian foals. In both cases, the genes are identified and programs put to place to decrease the incidence of the disease.
Here is some info about BLAD. IIRC, it was spread by use of one famous stud and his sons. He had a curious name, but darn it I can remember it.
There’s another disease that’s showing up in the QH that has something to do with horses coming out of Poco Bueno’s line but I can’t remember what it is. I THINK it might be like SCID but I can’t remember.
It’s really sad what humans have done to almost all of the horse breeds.
You’re thinking of HERDA (Hereditary Equine Regional Dermal Asthenia), also called Hyperelastosis Cutis (HC). It’s associated with the Poco Bueno line. Horses with this condition lack normal connective tissue within the skin. As a result, the layers of skin separate easily. This, of course, can be disastrous when the horse is ridden, harnessed, kicked, etc. Lacerations can also be hard to stitch. Not good.
SCID (Severe combined immunodeficiency) is another recessive disorder that shows up in Arabian and Arabian cross horses. As its name implies, affected horses lack a fully functioning immune system and generally die quite young.
:smack:
Thanks for the clarification. I was too brain dead this morning to keep anything straight!
It’s worth mentioning (well, maybe it is - who cares, I’m going to mention it anyway) that inbreeding doesn’t cause genetic defects. It makes it more likely that already-present recessive traits, many of which will be deleterious, will be expressed. The reason being that recessive traits need to come from both parents, and if one parent has it, the odds are much higher that it will also be present in a relative than in a random member of the population.
Good point, and this is one reason that inbreeding can have such an impact on domestic animal populations. HYPP and HERDA are so common in the Quarter Horse breed because they were introduced by prize-winning, hugely popular sires. Poco Bueno and Impressive were allowed to reproduce in a manner generally unheard-of among humans (tales of imperial harems aside), and their offspring were also allowed to sire many, many offspring. The genes from a handful of popular sires rapidly build up in the population.
This is partially the result of allowing AI breeding, which makes it possible for many more mares to be bred to a single stallion. Leading to decreased genetic diversity in the breed, as mare owners tend to cluster their breedings to top prize winning stallions.
Thoroughbred race horses, which prohibit AI and require live cover breedings, seem so far to have avoided these genetic problems.
Psst: In the case of Impressive, HYPP is autosomal dominant, both heterozygous and homozygous are affected (heterozygous less severely than homozygous).
It is also a problem in some wild populations. The Cheetah population in the wild was small enough at some point in the past (scientists beleive around 12000 years ago) that genetic defects due to inbreeding are a threat thier viability as a species:
http://www.smithsonianmag.com/science-nature/rare-breed.html
From what I’ve read, all Shar-Pei dogs in the US are descendants of the first four brought into the country. A veterinary dermatologist told me, “If you get a Shar-Pei, I guarantee you’ll be bringing it to me,” for the long list of skin problems they get.
You’re right. My hubby and I were talking about the problems inbreeding causes in horses and dogs the other night. Some animals are probably so inbred, they’re related to themselves :eek:
The most extreme case of inbreeding among animals is lab animals (rats and mice). Each strain (and there are several of each) is so inbred, they are effectively clones. All the deleterious recessives have long since been culled, so they don’t have any genetic defects except those induced by the experimenters (see knockout mice for example.)
A friend whos parents owned a breeding kennels told me that there were a lot of white Alsatian dogs around that were dangerous due to their being insane as a by product of inbreeding.