Breeding Practices
Basic Information Needed To Breed Rabbits Successfully:
Firstly we must define two basic terms, phenotype and genotype. The phenotype of an animal refers to the physical characteristics of that animal, (what we see). The genotype refers to only that part of the animal that is due to his genes (amino acids that transfer the messages from parents to offspring).
There are two primary reasons for the differences we see in animals, differences due to environment and differences due to the genes that the animals are carrying. Most breeders have little or no control of their gene pool. These would be phenotype breeders. They use little scientific approach to their breeding programs. And as we know, even a blind squirrel finds an acorn now and then. A consistently successful breeding program will usually make use of some form of line breeding. This is breeding genotype.
What is line breeding?
Line breeding is a simple concept that can be made to seem complicated. One must remember that line breeding is a program that produces animals from a single line of descent and from a common ancestor. It is a long ranged plan that a breeder is required to have an ideal animal firmly fixed and must be willing to pursue that ideal regardless of any breeding fads that might dictate otherwise.
Line breeding is built on the principle of "breeding like to like to get like." It affords the serious rabbit breeder the opportunity to set a type in the shortest amount of time. It also "narrows the gene pool."
The greatest danger in a line breeding program is that it intensifies all of the genes--good and bad. In other words, if you have a line of inherently quality show rabbits, breeding like to like quality to quality--should result in an higher quality line of rabbits. If, at the same time, this line of rabbits consistently lacks depth, then breeding like to like should result in an intensified line of poor-depth rabbits. In a line breeding program, you, as the breeder, find out what is good and bad about your program in a hurry. The only way to offset the intensification of undesirable traits in a line breeding program is to ruthlessly cull the undesirables from the herd.
With line breeding the breeder must use selection as a rigid tool in the process. Unless this is adhered to, the breeder will never attain his goal and the program will be doomed to failure. There are very few constructive line breeding programs and very few bloodlines that can be successfully line bred. The characteristics that must be maintained are conformation, soundness, fertility, disposition, coat colour, refinement, and females that exhibit the ability to raise healthy babies.
How should I begin?
The most significant part of the selection process begins with the foundation buck and foundation does that have common ancestry with the foundation buck. This will make the journey towards the ideal animal shorter. Otherwise the breeder will experience extra generations of breeding if the ancestry is not common among the foundation bucks and does. Many breeders of success believe that the does are the strongest part of the line breeding program and the bucks are providers of the necessary genes to improve the line.
The first step in line breeding is the mating of half-brothers and half-sisters that are produced by mating the foundation buck with the foundation does. The result of the half brother and half sister mating will be the second generation with the resulting offspring being double grandsons and double granddaughters. If the foundation does held common ancestry with the foundation buck uniformity would be apparent. One must not try to line breed to more than one common ancestor. The double grandsons and granddaughters will be genetic sons and daughters of the foundation sire. If each parent gave the next generation 50% of their genes, the double grandsons and granddaughters would carry 50% of the genes of the foundation sire. But because of the random division of genes in the parents, the influence of the four grandparents may not be transmitted in equal proportions. The offspring may bear a relationship to any one of the grandparents greater or less than the normal 25% relationship.
Is inbreeding different from line breeding and is it important?
There have been many questions asked of inbreeding, its safety, and it's benefits. Maybe I can shed some light on this subject.
Definition: Inbreeding is the mating of animals that are more clo sely related than the average degree of relationship within the population. Line breeding is the strategic use of inbreeding to improve traits found in one family line. The math used in line breeding is not very difficult, but it is quite interesting. The inbreeding coefficient is a percentage of the probable chance that genes will double when related animals are mated. It is often used in determining whether or not to mate two related animals because the higher the inbreeding coefficient is, the more likely it is that genes will double, whether they be good or bad.
Basically inbreeding is an intensified form of line breeding, with the sole difference being in the genetic closeness of the rabbits being bred to each other.
Among the advantages of inbreeding, is that it affords the surest and quickest method of fixing and perpetuating a desirable characteristic or group of characteristics, it tends to create lines or strains of animals that are uniform in type and it keeps the closest possible relationship to a desirable ancestor.
The disadvantages of inbreeding are that it almost certainly increases the proportion of undesirable breeding stock, with genetic abnormalities often appearing with increased frequency.
What to breed to what?
The different inbreeding coefficients are related to the different kinds of mating. In a half-first cousin mating, 1 common grandparent, the inbreeding coefficient is 3.12%. First cousin mating, 2 common grandparents, have a 6.25% inbreeding coefficient.
Both grandparent-grand offspring and half-sibling mating have an inbreeding coeffic ient of 12.5%. Parent-offspring mating and full-sibling mating, for 1 generation, have an inbreeding coefficient of 25%. Two generation full-sibling mating have an inbreeding coefficient of 37.5% and full-sibling mating for 3 generations have
an inbreeding coefficient of 50%.
By considering the inbreeding coefficient, the breeder can determine whether or not it will be beneficial for them to line breed two animals.
Inbreeding usually has a deleterious effect on many production characteristics. This is particularly important if the level of inbreeding increases rapidly. Where the rate of increase is slow then selection can be made to eliminate undesirable types and low producers. Inbreeding is particularly significant in the formation of new breeds where the original gene pool needs to be large enough so the undesirable types can be culled.
To put inbreeding into perspective the following table gives the rise in inbreeding for some close mating.
- Full brother-sister mating 25%
- Half brother-sister mating 12.5%
- Father-daughter/mother-son 25%
- Grand dam-grandson 12.5%
- Common grandparents (cousins) 6.25%
Thus, inbreeding can have genetic advantages but care must be taken so not to detract from favourable characteristics already established.
What is crossbreeding and how should it be used?
Crossbreeding (out crossing or out breeding) is the opposite of inbreeding, i.e.: increasing the number of heterozygous pairs. This is commonly known as "widening the gene pool." Out breeding is the mating of animals, which are less related than the average relationship of the population. Thus out breeding is practiced most commonly between families. In crossbreeding, heterosis or hybrid vigour is often a common calculation in determining whether or not to cross two breeds. Heterosis is the degree to which an offspring deviates from its parent's breeds
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