What We Can Learn from Test Breeding

(pictures to come)

There is a lot that can be learned from test breeding, however, it is usually only used to test for the presence of easy to identify traits - typically those that are determined by a single gene. People don’t usually test breed for type - developing type is a much slower process and can take your whole career.

Test breeding is used to determine if a particular animal is carrying a particular color or some other recessive trait. Curiously, we often test breed for colors when we are looking for a color we want, but we test breed for other traits (like wolf teeth or split penis) when we are looking to eliminate something we DON’T want.

When you do a test breeding, you will always have one parent who either shows the trait or who you KNOW is carrying it. Breeding two animals together when you don’t know if EITHER of them is carrying the trait you are looking for may turn up nothing for a long time.

Since we are looking to see if a particular rabbit is carrying a specific recessive gene, we will want to breed to a rabbit who is KNOWN to carry that gene. Of course, if we are trying to see if this rabbit is carrying the genes for wolf teeth for example, we would NOT breed from an animal that actually HAS wolf teeth. For that matter, you probably shouldn’t even keep any rabbit that is known to carry undesirable traits. If this is your reason for test breeding then you would breed related animals of the line you suspect has the trait. If it turns up in the litter, then BOTH parents should be eliminated from your breeding program.

If you are looking for certain colors though, things are different. In that case you would ideally breed your ‘test animal’ to one that has both copies of the gene you are looking for. For example, if you are looking to see if a doe is carrying chocolate, then breed her to a chocolate. If she produces even ONE chocolate baby you know for certain she is carrying that gene. Beware though: genetics is a numbers game. If you breed a suspected chocolate carrier (B?) to a chocolate (bb) it is possible for the entire litter to come out black (Bb). That is because the likelihood of producing a chocolate from this mating is 50/50 - but that likelihood applies to EACH kit, NOT to the litter as a whole. Just like it is possible to toss a coin 100 times and for it to turn up heads every time, it is possible for each kit to end up black. Still, chances are good that you will end up answering your question - and you are much more likely to be able to answer your question if you breed to an animal that is homozygous (i.e. has both copies of the same gene) for the trait you seek than if you breed to one who is heterozygous.

There are a few animals that can be particularly useful in a test breeding, and those are the ones who carry the most recessive genes. A lilac self, for example, is homozygous recessive for almost everything: it is aa bb C- dd E-. You can use it to tell if another animal is carrying self, chocolate, OR dilute. A lilac tort (or crème) takes it one step further: it is aa bb C- dd ee.

Another animal that can be valuable for test breeding is a red-eyed white (albino). It carries cc on the color locus and that means that ANY non-white babies are showing the C-gene from the test parent. Have a castor and want to know if it’s carrying chinchilla? Breed to a white. Do you suspect your otter is carrying Californian? Again, breed to a white. It is important to remember though that REW is the result of the cc gene, which removes all color. The white is effectively HIDING the actual color. That means you will have no way of knowing what else the white is carrying (unless you know the genetic make-up of the parents). If you want to know what your REW is carrying…. given what we now know we should… breed it to a lilac of course! Many pedigree programs let you track colors so start tracking your colors and have fun!

  • care/test_breeding.txt
  • Last modified: 2017/06/07 17:29
  • by becker