Re: Adoption
You shouldn't house rabbits with guinea pigs. There are always risks with breeding, but (my emphasis) taking in a needy pregnant guinea pig is rewarding. Usually the mother does most of the work, but yes, if there are complications, experience does help.
Just wanted to see if I could clear this up as I took it a different way--the first sentece about rabbits being housed with guinea pigs seems to be a totally different thought than "there are always risks with breeding, but taking in a needy pregnant pig is rewarding." In the first sentence they are addressing the subject of rabbits and cavies playing/being housed together, and after that they change the subject and are then addressing the topic of adopting pregnant piggers. It did seem "mashed togehter" at first, but if you look at the sentence, the beginning of the second sentence is simply an auxilliary clause introducing the concept of risky pregnancies in pigs and the difficulties of adopting them (notice the use of the conjunction BUT after the comma, thereby connecting the two phrases); not a statement referring to the previous sentence. I just wanted to try and help before a fight started =) hope you don't think I was butting in!
Regarding the genetic factors, I'm not sure how it happens, but I am fairly certain that different breeds can be born to the same litter. My two boys were born from the same litter (My friend had an "oops" pregnancy and so I know this for a fact). However, my Miko is a peruvian/abby mix and my Taiko is a sheltie (no signs that he is any other breed.) I think that it is the same as with human genetics (lets see if I can recall gr.11 biology):
Both the mother and the father are carriers of genetic traits called alleles. Some are dominant alleles and some are recessive. Let's take for example the trait of eye colour. Brown eyes are dominant over blue eyes, so if one parent has brown eyes, it is still possible that they would carry the gene for blue eyes without displaying it (their alleles would be BBbb, B being dominant brown and b being recessive blue). The brown is displayed over the blue because it is dominant and hides the recessive trait. If the other parent had the same BRbl, it is still possible that they both pass on the recessive blue allele to their offspring and so their children could have some of the following makeups: BBBB, BBbB, bbbb etc. so therefore a child whose parents both have brown eyes may still have blue eyes if their parents are carriers of the recessive gene. Similarly, their siblings may have brown eyes because they inherited diffrent combinations of alleles from the same parent. I believe this is genetic diversity, or some concept like that.
Similarly, guinea pigs in a single litter may posess different genetic traits based on the genetic makeup of their parents, and which genes are dominant and recessive, and which traits are passed on to each individual pig. Since mulitple births in the case of mammals like guinea pigs are not ones which result in the offspring being identical (same idea as fraternal twins), each pig is a unique sibling who inherets unique alleles from each parent. Some litters may have pigs that are almost identical in breed and colouring, while others may have completely different appearances. Why? Well, let's assume the trait for abbysinian is dominant, A, and the trait for long hair is recessive, l, and that each parent is a carrier of both the A allelle and one l allele, then therefore the offspring may only inherit the dominant allelle for the Abby trait, the recessive allele for the peruvian trait, or a combination of the two resulting in a mixed breed, or a completely Abby pig carrying the recessive trait for long hair that could be passed on to their offspring, etc. And so you could have some pigs that appear to be completely Abby or peruvian, even if their parents or siblings are not, simply based on whether they inherited dominant genes (in this case Abby) that mask the recessive (in this case, Peruvian) alleles. So theoretically, a litter of two pigs from these parents could have one pure Abby and one pure Peruvian due to this genetic diversity and the random nature of the inheritence of these allelles.
Now please remember that the above genetic
combinations are most likely completely wrong, but the
idea behind it is the correct one. But do cut me some slack, It's been 4 years since biology, so I think I've done pretty well considering that fact
Anyhoo, hope that helps!