Observations on the early development of embryos from repeat breeder heifers [morphology of bovine morula and blastocyst]
1980
Linares, T. | King, W.A. | Ploeen, L. (Sveriges Lantbruksuniversitet, Uppsala. Dept. of Obstetrics)
Embryos were collected from 8 single ovulating and 4 superovulated repeat breeder heifers (RBH), and 7 single ovulating and 2 superovulated virgin heifers (VH), slaughtered at different intervals after heat (day of standing heat =.0). The collected embryos were morphological classified with the aid of a phase contrast inverted microscope into 3 groups: normal, in the process of degeneration and degenerated, and the diameter of the embryo and of the cell mass and thickness of the zona pellucida were measured. After classification they were either stained with aceto-carmin, processed for cytogenetics or for further morphological studies. The recovery rate from single ovulating and superovulated RBH was 63 per cent and 51 per cent respectively, whereas for VH it was 100 per cent and 50 per cent. Of the 60 embryos collected from RBH only 27, of which 20 were 4 days or younger, were classified as normal. This is in contrast with the embryos collected from VH, where 27 out of 33 were in the expected stage of development. The RBH occasionally produced ova that were fertilized and underwent normal development up to the stage when they were collected, however, in most cases abnormalities occurred and there was considerably more variation in the appearance of the embryos from RBH than VH. It is suggested that the abnormalities arise while the embryos are in the oviduct and that many cannot be detected morphologically until formation of the blastocyst in the uterus
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