Animal breeding / by A.L. Hagedoorn.

  • Hagedoorn, Arend L. (Arend Lourens), 1880-1953.
Date:
[1939]
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Animal breeding / by A.L. Hagedoorn. Source: Wellcome Collection.

    139/410 (page 107)
    Breeding-out Recessive Qualities 107 pedigrees and from analogy with very similar instances in human beings, as well as in rats, that we are dealing with inherited defects. With both troubles the abnormality is most frequent in certain blood-lines, and it often happens that the first cases that come under our notice all trace back to some common ancestor. When such instances first come to the notice of a consulting geneticist, they tend to be already widespread, as at the outset the breeders do not think that defective heredity can be the cause. When an abnormality is seen in quite young animals the aberrant pups are simply killed and disappear. When they become more frequent the abnormality is seen to run in certain families in the way all recessive qualities do, that is to say that certain matings give abnormal pups and others never do, while in the beginning abnormal bitches mated to unrelated studs produce apparently normal litters. In such instances the remedy that seems obvious is test- mating. To be sure that an individual pedigree dog is homo¬ zygous in respect to the gene the blind (or deaf) dogs are defi¬ cient in, all we have to do is to mate him or her to a few of the abnormal animals, for if such matings give only normal pups the tested individual is free of the inherited taint. In theory we could establish a group of tested homozygotes that would be guaranteed free. I have had numerous discussions with individual pedigree breeders and stud-book officials on the subject, and I have come to the conclusion that this is not at all what I could recom¬ mend. There are several reasons for this. It so happens that blindness occurs in three separate breeds of show dogs, and hereditary deafness in two others in a certain group of breeds very popular with handlers and exhibition breeders. A breed society sponsoring one of those breeds would almost certainly injure that breed in the public view by the mere fact of openly discussing ways and means of breeding out a serious defect like progressive retina degeneration. The dog-buying public would simply turn away from that breed with all the blind pups, and patronize some other and very similar breed in which no talk about blindness has yet leaked out. Again, think of the number of pups, slowly getting blind, that would have to be deliberately produced to test-mate several studs to blind bitches, and especi¬ ally of the number of valuable fashionable show bitches that would have to be test-mated to blind studs. Would we be sure