Abstract
Ninety-five gilts and sows which had shown impaired fertility were obtained in 1948 and 1949 from Illinois swine producers and from the University of Illinois for study. Of these, 16 were not included in the study for various reasons. Of the remaining 79 females 53.2% conceived on the study but they must still be regarded as being "hard-to-settle." The rest showed various abnormalities which were responsible for their sterility or low fertility. The most important abnormalities were: tubal aberrations, cystic follicles, and blind or missing portions of the reproductive system. Very little evidence of complete embryonic mortality in individual females was obtained in this sample. The difference between the number of corpora lutea and the number of fetuses indicated that about 26% of the ovulated eggs did not develop into embryos. Copyright © . .