Author Debbie Cave
of Azure Chinchillas
Breeding Techniques
Inbreeding
A term used to describe animals related to each other that are bred together. This term is usually used for more closely related individuals in particular.
It is possible to calculate the amount of inbreeding that has gone in to producing an individual - this is called the "inbreeding coefficient".
Inbreeding can increase the homozygosity of offspring (so that they can closely resemble their parentage) and it reduces variation within a line. Great if you have superb breeding stock as you will be able to maintain and even improve on quality!!
This is all very useful initially, but sooner or later a point can be reached where no further gains can be achieved.
Inbreeding can also expose harmful recessive genes (increase possible genetic defects) which will eventually contribute to a lack of breeding performance, called "Inbreeding Depression".
Line-Breeding
A type of inbreeding where one individual appears in a pedigree more than once.
A simplistic example is to breed a daughter back to her father and their female offspring back to the grandfather, etc.
Not only can a line be based on a male chinchilla, but it is as viable to base the line on a female chinchilla too.
Once again, line-breeding can expose harmful recessive anomalies and is equally subject to "inbreeding depression". It also makes the assumption that no improvement can be made on the original chinchilla that the line is based on.
The main value of line-breeding to that it can maintain the phenotypical purity of the offspring in relation the positive qualities that the original chinchilla had, and will help to "fix" those qualities within a line.
However, you do need to carefully select the offspring you wish to breed from.
Cross Breeding
(or outcrossing)
The breeding of individuals from unrelated bloodlines.
If separate bloodlines are bred together then the result will be offspring with hybrid vigour. In other words, the dominant genes from each bloodline will suppress the harmful recessive genes.
Repeated cross-breeding can result in very variable offspring. In fact the cross-breeding of two chinchillas from separate bloodlines will result in some very average results, UNLESS they are both from very carefully bred bloodlines.
Sometimes cross-breeding is utilised to reduce inbreeding-depression within a bloodline. Once out-crossed the line is then line-bred or inbred again. This technique is called "cyclic-outcrossing" and is my breeding method of choice.
Rotational Cross-Breeding
This is the term used to describe a method where the breeding herd is divided into three (or more) very distinct and unrelated groups.
The males and females within each group are bred together to produce an F1 generation. All F1 females that are produced stay within their own group, but the F1 males are moved on to the next group for breeding, and so on and so forth, for each subsequent generation produced.
This method reduces that amount of inbreeding that is necessary. However, the breeder will still be able to be selective over the breeding stock that is used each generation.
Rotational cross-breeding is particularly useful in preserving rare or unusual colours.
Phenotypcial Breeding
This term describes the breeding together of unrelated animals that look similar or both have the same desirable phenotypical characteristics. This is what most novice breeders initially start off by doing.
This is all very well, but because the genetic makeup of the breeding adults will differ, the results in the offspring will be pretty hit and miss and certain characteristics will not "fix".
Highly rigorous selection of the offspring for future breeding may enable some improvement, but this is rare.
Corrective Breeding
Again this is the term used when breeding unrelated animals together, but this time they have been selected so their strengths and weaknesses compliment each other (or cancel each other out).
This is a good technique for correcting any particular faults within a line (i.e. weak neck for instance). Once again the offspring will be highly variable and will need careful selection for future breeding by the breeder.
Inheritability
Some features, such as colour, are clearly highly inheritable. The amount that any one feature is inherited is called the "degree of heritability". Here are some basic examples:
Features with a low degree of heritability
Litter size
Survival rate of the offspring
Features with an average degree of heritability
Temperment
Weight
Features with a high degree of heritability
Conformation
Colour
Selection For Breeding
There are two ways of selecting breeding stock. One is to concentrate on one particular characteristic at a time and select for that one outstanding feature, regardless of any others. Once the goal for that feature has been achieved, offspring are then chosen for another characteristic.
The other method is to assess and "score" potential breeding stock for all the desirable characteristics and only choose those that "score" highly overall.
This second system is slower that the first system but is thought to achieve better overall results in the long-term.
Breeding with Mutations
Breeding from healthy animals goes without question.
But mutation breeding is not 100% down to health - it is also down to the genetics (genotypes) and the way they influence a particular strain or bloodline.
Mutations are generally inherantly "weaker" than the natural form of any animal.
(mutation meaning = sudden change)
In the wild state - some mutations (i.e. albinism) are usually picked off fairly quickly by predators - and are not able to breed.
Only strong mutations (adaptions) evolve and survive - hence what you see in the "wild-state" (i.e. standards) are usually the fittest and strongest.
If you look into the history of the first chinchilla mutations (that appeared in captivity) - they were very weak, sickly animals indeed - that would most certainly had not survived if it had not been for major human intervention.
In fact - the first beige had the most dreadful teeth problems and had to be kept alive long enough to breed.
Breeding back to standard (the natural form) - helps to counteract any inherant weakness that may be associated with that particular form of mutation - (i.e. there may be certain undesirable characteristics on the same loci on the chromosome as the desirable ones - and outcrossing to standards may minimise undesirable effects).
However, in certain instances mutation to mutation pairings are unavoidable - but they should be done with care (not to mention a degree of knowledge)!!!
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