Guinea pig genetics

[ohbrazil]

Okay, first I would like to clear up that I am not a breeder, I am not thinking about breeding guinea pigs, or promoting it in any way!

I was making my cup of coffee this morning and I thought about pet stores. If they have both genders in a cage, from the same litter, and they mate, does it create genetic problems in the offspring? I know about fatal pigs, but what are the chances and realities of sibling mating? I realized I only understand this for humans, and I was curious.

[VoodooJoint]

One mating between relatives --siblings, mother/son, father/daughter-- usually will not create any defects in the animal although it will strengthening any problems already inherent.

Problems may start to arise if another close line breeding is performed by the offspring of the original linebreeding.

[dextersmycutegp]

I have a question about this: I got Holly from a petstore (oops) where she had evidentally been bred to her brother. I am not sure if Holly was accidental herself but I think so, so that probably means that Holly's dad is also her uncle.
Could Dexter and Midnight have some genetic problems from that? What are the signs?

[aqh88]

Signs are all completley different. It depends what genetic abnormality they may have gotten. Some examples are lack of blood clotting in humans(hemophilia) and potassium intolerance leading to muscle spasm and seizures in horses(hypp, aka impressive syndrome). It could be a weakened organ, an inability to digest or absorb certain foods/nutrients, cancers, mental problems, vision problems, tooth or bone problems, and an uncountable amount of other potential disorders. It can take several generations of inbreeding because oftentimes a genetic disorder does not cause a problem when there is only one gene. So say the father has a mutated gene that could cause health problems but does not unless you get 2 of them. He gives birth to offspring from 2 different females. 1 male baby from one of the females has the gene and 1 female baby from another female has the gene. If you breed these 2 offspirng together the babies from them can get 2 of the gene since you get 1 gene from each parent. That causes those offspring to have the disorder. This is even an example of more distant crosses. The closer they are related ie daughter back to father the greater the chance of the disorder showing up in fewer generations.

[Luvthempigs]

But, remember. These genetic problems will ONLY occur if they were in the original genetics. Not all inbreeding produces sickly animals.

[salana]

Basically, anything that one member of the family develops (heart problems, bladder sludge, ovarian cysts, cancer), the others have a very high risk of getting it too. You might be lucky. You might be very very unlucky. You just have to keep an eye on all of them, as they're really about the same age, especially once they hit a year and mom is only 3 months older than the babies.

[Matt & Guins]

As mentioned, a one off or occasional "in breeding" wont result in problems.

But the thing is with petshops, is that those babies in the petshop may already be the result of brother/sister mating - the parents may be brother/sister (either a sow bought pregnant, mis sexed cavies who end up breeding, or deliberately purchasing a boar/sow).

So if the babies breed, then they are 2nd generation inbred (or 3rd, or 4th - who knows!)


Matt

[spoonyspork]

Something I noticed with inbreeding: for some reason, by generation 3 or 4, many small animals (that I've seen bred) end up with red eyes. I knew someone who purposefully bred hamsters and gerbils, and didn't think about the fact they were breeding mothers to fathers, sisters to brothers, etc. They all started with black eyes, had a few litters with a mixture, and by the time she finally saw the error of her ways, all of her animals had red eyes.

When a huge mess with guinea pig mis-sexing happened with another friend, all of her first started with black eyes, and by the time she got everything straightened out, every one in beyond generation 2 had at least one red eye. The pregnant girl I took in from that group also had one red eye (and not a spot of white on her), and in her litter she had two with one red and one black eye, and two with both red eyes. She was gen 4, and the boar was gen 3.

In my SO's group, both the boar they took in and all his siblings, and the already pregnant sow (who was both daughter and mate to the boar) and all *her* siblings had black eyes. She had two black-eyed babies, one with one red and one black, and one with both red. The babies stopped there, of course.

Another thing I noticed, at least with the two examples of guinea pig inbreeding I was witness to, was the shrinking of size with each generation. My girl's generation were all the size of my hand, though the babies she had were 'normal' sized - that is, slightly less than half the size of my hand. And there were 4 of them. That girl was VERY lucky she had those babies without a problem. They were almost fully grown by the time I had to give them up, and they were slightly smaller than momma. I suppose it'd help to say gen 1 were absolutely HUGE piggies. My SO's girl's babies were actually smaller than normal when born - so small he at first thought beetles had gotten into her cage. Momma herself was pretty small, though the father was about the same size as my Hee. The babies all grew to be the size of my hand.

I'm guessing traits that were probably hidden by lots of more dominant genes were slowly brought to the surface by steadily smaller genetic diversity.

[dextersmycutegp]

There isn't anything really weird about Holly, Dexter, and Midnight, yet. Although Midnight is extremely small, she's barely 1 1/2 pounds at 9 months old. Dexters teeth are a little crooked too, but they correct themselves.
Dexter does have ruby eyes, but he is also brown roan/himilayan. He is a really weird color, could that have anything to do with being inbred? He has roaning on his face and body but he also has himilayan markings (dark face, feet, underside, ears, with a light cream colored body)

[aqh88]

Red eyes are not by themselves a cause of inbreeding but the genes that cause red eyes are recessive to most other genes. Both parents need a gene for a color that causes red eyes to get red eyes. So when you breed 2 dark eyed pigs you have no better than a 25% chance of getting red eyes. If you do get a red eyed pig though and breed that back to one of your dark eyed parents you now have a 50% chance of red eyed offspring. Your concentrating the gene pool and so increasing the chances of getting red eyed offspring. You can also get red eyed pigs from breeding completely unrelated ones but unless your starting with 2 red eyed pigs already your chance is low because they may not even carry the gene for it. Odd colored coat patches are also more likely to show up in inbreeding because it may be a gene specific to 1 guinea pig and breeding back to that guinea pig enough will cause it to show up on more pigs. How do you think they spread new coat colors and hair types? 1 or 2 pigs suddenly were born with it and they bred that pig to others until it spread enough. There are gene mutations showing up all the time but most disapear unless someone lacking a brain decides to start inbreeding a bunch of animals.

All of these problems though can just be poor genetics and not actual inbreeding. Even if you breed unrelated animals if they have problems like bad teeth it has a chance of being passed down. Unless you know the history it's impossible to tell if an animal is inbred or just has bad genetics anyway.

[evilnumberlady]

Originally Posted by Luvthempigs

But, remember. These genetic problems will ONLY occur if they were in the original genetics. Not all inbreeding produces sickly animals.

One thing I learned in my genetics classes in college is that any animal as complex as a human or even a guinea pig has enough genetic materials that goes into making them that they WILL have some recessive "bad" genes.

My professor estimated that every human being is carrying around at least 3 genes that, if they had two of instead of just the one, they would be dead.

That's why inbreeding is ALWAYS bad. The chances of a baby having a genetic disease is MUCH higher when the parents are related because people who are related tend to be carrying the same "bad" recessive genes, instead of non-overlapping ones. Gentic disease is always a greater risk with inbreeding, even if the animals appear completely healthy.