The longer you are in rabbits the more you get a feel for how the whole process of breeding works:). After breeding for awhile and talking to people who have raised any breed for years and years, you see that there is a definite "method" of developing your herd and maximizing the potential of your stock. Three basic breeding methods exist to accomplish this task, but they need to be applied consistently and in a well-planned fashion.
The first method of breeding used by rabbitry managers is known as "OUTCROSSING". Outcrossing is the accumulation of unrelated stock to introduce specific traits that are lacking in an existing line (for ex. wool or type qualities), but it may also be employed to refresh a gene pool and lend 'hybrid vigor' to an excessively inbred line.
The second system of breeding is known as "LINEBREEDING", which is simply the combining of individuals who are less closely related--for ex. mother/son, grandfather/granddaughter, aunt/nephew, or cousins. Line-breeding is a vital ingredient in the development of a high-quality, uniform herd, and increases the homozygosity of a herd as well.
The third method is known as "INBREEDING", which basically amounts to brother/sister matings and the closest possible pairings. Inbreeding is essential in any herd because it enables you to 'lock in' certain traits and expose others. Brother/Sister pairings bring out the problems and recessives that have been lurking in a line and allow them to be dealt with, PLUS it is an excellent way to "set" desirable qualities as inbred litters typically have an above average ability to pass good traits onto their offspring no matter who they have been bred to. Inbred animals are important to any breeding program because they make it easier to predict results.
When first starting out and working to develop a quality line, it is important to decide which traits are essential in a good herd. What are the most important qualities of your breed, and what traits are vital in order to produce animals capable of competing on a showtable or producing high volumes of wool (in a Wool producing herd)? It is a good idea to pull out your Standard and read exactly what a good example of your breed should look like and what characteristics need to be emphasized. If you are a list person, write down the traits you are looking for and the qualities you want so that you will have a clear idea of where to begin:).
Once you know what you want/need in a good herd, begin buying your stock. Research breeders and lines that have the qualities you are looking for, and buy several animals to get started with. There are different modes of thought as to whether it is better to buy an animal for it's individual qualities or because of the bloodline it comes from, but in reality either approach should work if you cull hard enough and make rational breeding decisions along the way.
After you find the specimens that you want to start out with, begin breeding them together in different combinations until you see which ones work, and then select the best babies from each litter to breed back to outstanding animals within the same family. This is the beginning of a 'line-breeding' program, which should go on until you have isolated desired traits and the quality of your animals is dramatically improved. Line-breeding is the phase of development that a breeder spends the most time on because it is the "building" phase of a line----the work that is done to produce the rabbit you want. It is important during this period to avoid outcrossing again, because new stock will also bring with it a whole new set of genes that need to be tested for and bred around. There is NO such thing as the perfect rabbit or perfect line either, so the only way to make one close is to linebreed diligently so that the good genes collect and duplicate themselves without the interference of outside bloodlines. IF you find that you have made a mistake and failed to bring in a trait that cannot be produced without crossing out then you will have little choice but to bring in more stock. Every time you do this you will set yourself back and it will take longer for your herd to become homozygous, so always be sure that is 100% necessary before you do it:).
In-breeding comes at the very "end" of linebreeding, or if you have two outstanding rabbits that you want to concentrate the qualities of and produce offspring that will transmit those traits quickly and easily. If you have two examples of the breed that you want to serve as a model for future generations, then breeding brother to sister is advisable and a good idea. A mixture of good and poor-quality rabbits is likely to result in the litter because inbreeding concentrates the good and bad qualities of a line, but strict culling can make pairings like this a success, so it is a good, long term practice to employ in any barn:).
So anyhow, this is an article about the different breeding practices used to improve the quality of a herd. When line-breeding becomes intense and the vigor of a herd begins to decline as the genes becomes more and more similar, then it is often necessary to outcross again and refresh your gene pool. In this case you can either find a rabbit that is distantly related to your line, or buy a completely unrelated animal and breed it in just enough to invigorate the herd, and then revert back to your original plan. Also, be sure that the new blood you introduce for this purpose is always a doe, since a buck will spread his genes far and fast before you've had the chance to discover whether his compatibility was good.