Inbreeding and Line Breeding 
The question of introducing new blood into his herd is the first that 
seems to confront the beginner in rabbitcraft, the belief being general that 
it is not good practice to mate the sire to his daughters or a young buck 
to his sisters or dam, and that weak, unhealthy stock results from such 
matings. Inbreeding, linebreeding, and outcrossing in rabbits has been 
the subject of more discussion among breeders than any other topic we 
know of, and it would be presumption, indeed for the writer to attempt: 
anything more than a review of the elementary principles of the subject in 
a work of the present nature. As concerns fur rabbit farming, however, it 
is well for the breeder to consider first what objects he desires to attain 
before deciding whether to inbreed or outcross. 
The mating of closely related animals, such as brothers and sisters of 
the same litter, or from two litters of the same parents, or sire with 
daughter and buck with his dam, is termed inbreeding. Various milder 
forms of inbreeding, using no blood except that of individuals of the same 
herd or herds closely related, is known as linebreeding. To outcross is to 
use breeding stock from a totally unrelated herd or strain. 
Inbreeding has been carefully analyzed in “Inbreeding and Outbreed- 
ing,” by Edward M. East, Ph. D. and Donald F. Jones, D. Se. (Lippincott 
Co., 1919), in the following language: 
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“The only injury proceeding from inbreeding comes from the inheri- 
tance received. The constitution of the individuals resulting from a pro- 
cess of inbreeding depends upon the chance allotment of characters pre- 
existing in the stock before inbreeding commenced. If undesirable char- 
acters are shown after inbreeding, it is only because they already existed 
in the stock and were able to persist for generations under the protection 
of more favorable characters which dominated them and kept them from 
sight. The powerful hand of natural selection was thus stayed until in- 
breeding tore aside the mask and the unfavorable characters were shown 
up in all their weakness to stand or fall on their own merits.” 
“Tf evil is brought to light, inbreeding is no more to be blamed than 
the detective who unearths a crime. Instead of being condemned, it should 
be commended. After continued inbreeding a cross bred stock is purified 
and rid of abnormalities, monstrosities, and serious weakness of all 
kinds. . . . As we shall see later, vigor can be restored, but it may even 
be increased, due to the elimination of many unfavorable factors.” 
When a breeder of fur rabbits finds that the young from a sire and 
dam of outstanding excellence are quite satisfactory as to coat color, vigor, 
size, and utility type of body, there is usually no reason why. the daughters 
cannot be mated back to the sire. While a decline in vigor and fertility 
may result from such matings, it is not certain that it would so result, and 
there are quite as many changes that an outcross (mating the daughters to 
a sire of another strain) might result in a litter having undesirable coat 
color, poor fur quality, and inferior type, or shape of body. Whether or 
not the buck of the original pair should be mated to his granddaughters 
and greatgranddaughters, depends on the qualities appearing in the young 
from mating with his daughters. If no decline is noted in vigor, size, or 
health, and if the fur texture and color are equal to or show an improve- 
ment over that of the original parent, the dangers attendant to close breed- 
ing have not appeared, and the breeder may safely stay within the herd or 
-strain thus established. On the contrary, if the young from such matings 
are infertile, runty, and of low vitality, an outcross to a sire of an unre- 
lated herd is likely to result in increased vigor, health, and in bodily im- 
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