The Maturation Process of the Ovum of Swine during Normal and Induced Ovulations

Abstract

The initial stage of the maturation process of the egg nucleus begins about 5 hours after the onset of heat and proceeds to metaphase II just prior to ovulation. During the ovulatory process and until fertilization occurs, the egg is static insofar as observable nuclear changes are concerned. It has one polar body and the chromosomes of the egg nucleus remain in the metaphase II. The granulosa cells in the discus proligerus undergo a radial dispersion or scattering at the onset of maturation and just after ovulation this gelatinous material surrounding the eggs unite in the fimbriated end of the oviduct to form the egg plug. Gilts in the luteal phase of the estrous cycle treated with gonadotropins produced follicular ova that were undergoing maturation, tubal ova that were in the second maturation stage and uterine ova that were fragmenting. Gilts treated with gonadotropins during the follicular phase of the estrous cycle produced follicular ova that were in some stage of maturation, tubal ova that were in the second maturation stage (except one that was in interphase) and uterine ova that were in the second maturation stage or fragmenting. Ova from induced ovulations reached the same stage in the maturation process as those from normal ovulations, and some of these were found to be capable of fertilization when the gilts were force bred. Ovulation was induced in gilts during the various phases of the estrous cycle by a single injection of 35 AU of gonadotropin but heat did not occur in any animal injected with gonadotropin.