Production measurements affected by X-irradiation of chicken semen

Single Comb White Leghorn (S.C.W.L.) and Dark Cornish semen was X-irradiated with 1000 r. and introduced into S.C.W.L. hens to produce S.C.W.L. and crossbred chicks. The irradiation reduced the fertilizing capacity of the semen about 25 percent and the hatchability of the embryos about 38 percent. Semen of the two breeds was affected differently since there was much less alteration of embryonic development among purebred, S.C.W.L. chicks than among Cornish-sired crossbreds. As is typical, crossbred chicks gained weight faster than purebred S.C.W.L. irrespective of radiation damage. After irradiation, live weight was 4 percent less at 16 weeks of age for the crossbreds but no substantial effect on growth was evident for the S.C.W.L., although they were significantly heavier at hatching in the irradiated population. The rate of egg production in the first 30 days declined 15 percent under pressure from the irradiation damage. The distribution, as well as the frequency, of embryonic mortalities changed after parental semen irradiation. The majority of embryonic deaths occurred during the first 6 days of incubation with a coincidental decrease in the proportion of deaths occurring late during incubation. Posthatching mortalities were not affected for S.C.W.L. but were doubled for Cornish up to 16 weeks old.