Parents’ Age Unrelated to Leucosis in Progeny

Coles (1955) stated that “birds in their hen year failed to transmit resistance (to leucosis) because of incomplete ability to do so with increasing age” and that “a parent bird may increasingly fail with age to transmit genetic resistance to its offspring.” Age has no influence upon the genotype of an individual bird nor does it determine which genes are distributed to the functional gametes. Coles did not specify any mechanism by which age of the dam might influence resistance of her progeny, and the data given in support of his theory were scarcely conclusive. However, since in mice a non-chromosomal influence of age of dam on the incidence of spontaneous leukemia in her progeny is known (MacDowell, Potter and Taylor, 1945), it seemed desirable to examined our records for any evidence that might support Coles’s theory. From the records of our White Leghorns for the six years, 1949 to …