Animal genetics / Frederick B. Hutt.

  • Frederick Hutt
Date:
[1964]
Catalogue details

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

Credit: Animal genetics / Frederick B. Hutt. Source: Wellcome Collection.

    532/578 page 510
    510 ANIMAL GENETICS different diseases, and believe that several viruses are responsible for the differing forms. In any case, only two effective control meas¬ ures have been developed thus far. One of these is to isolate the chicks at hatching, and to keep them away from adult birds ( which are believed to be the reservoir of infection ) until the young pullets are four to five months old. By that time they are nearly all resistant and can safely be returned to infected premises. The effectiveness of this practice has been shown in Fig. 15-5. FIG. 22—2. A White Leghorn pullet showing at six months of age a charac¬ teristic position of paralyzed birds stricken with neurolymphomatosis. (Courtesy of Cornell University, and of Cornell University Press; from Genetic Resistance to Disease in Domestic Animals, by F, B. Hütt.) The other method of control is to breed strains resistant to the disease. The feasibility of doing so has been demonstrated at Cor¬ nell University and elsewhere. Most large-scale poultry breeders are now selecting for resistance to leucosis, but, as usual, the prob¬ lem is complicated. For one thing, no satisfactory method is known by which birds under test in each generation can be given exposure to the disease by natural channels of infection. To some extent brooding them near old hens is useful; but this does not always en¬ sure exposure severe enough to differentiate resistant and susceptible families. A measured dose of tissues from diseased birds shot with a syringe into the abdomen or muscles of the chick is of little use because that by-passes the resistance to natural infection, and re¬ sultant mortality gives no clue to families that can resist natural
    No text description is available for this image
    No text description is available for this image
    No text description is available for this image