Line- Cross & Inbreeding

BREEDING METHODS

The following are breeding methods that may be used to develop or preserve a line. It is important to know WHAT the purpose of each are and WHEN to use it.

CROSS BREEDING:

Cross breeding is where two unrelated rats are bred. This is to introduce new genes to an existing line that is either too inbred or where a new colour / marking / coat or ear type is introduced to the line. It is always risky to cross breed to an established line where animals have good health, temperament and/or longevity, as it may influence these in a negative way. It is important to be strict when selecting these individuals and “test breed” and evaluate the line for a few generations before introducing it to all your lines.

LINE BREEDING:

Line breeding is where an established line with good health and temperament and the desired colours and markings, are maintained. To do so individuals that are related are continuously bred together, but no close relatives. (See Inbreeding) Niece x uncle, nephew x aunt or cousins may be bred to maintain or “line breed” a line.

INBREEDING:

Inbreeding is where close relatives are bred, like brother x sister, father x daughter or mother and son. Inbreeding may be used to test a line for any hidden health or behavioural problems. It may also be used to express a recessive gene (genotype) for a specific colour or marking that is not expressed in the rat (phenotype). By breeding these animals together, the recessive gene will double up in some individuals and produce offspring that express the desired (recessive) colour or marking. As soon as the line is established, one should line breed to maintain the line. Although rats may be inbred for many generations without showing any abnormalities, it may compromise the health of the line in the long run. Do not continuously inbreed for no apparent reason.