| The objectives for present study were to prove the in vitro embryo production ability for oocytes from different pregnant period, and to observe the morphology and histology and ultrastructure dynamic features of corpus luteum for the all pregnancy period.Spring-born Hereford x Friesian heifers grazing pasture were used in the experiments. The estrus and ovulation in the heifers were synchronized using a regimen of intra-vaginal controlled release device containing 1.9 g progesterone for 10 days. 158 were pregnant by embryo transfer or artificial insemination, and were necroscopy at arranged day from d!4-d280.From study the morphology and histology and ultrastructure of corpus luteum, and the distribution of follicules for the all pregnancy period, the following conclusions were got: 1) The ovary length, wideness and thickness increase up to d26 of pregnancy. After that, the size increase stop for a few month, then the length still tend to growing slowly, and width is decrease, and high is constant. 2) The weight of ovary for the pregnant cow decreases after 3 months pregnancy, and the corpus luteum weight decrease slightly; the ratio of corpus luteum and ovary is low (PO.05) at early pregnancy stage and late pregnancy stage, all other stages are no significant difference (PO.05). The loss of ovary weight is mainly from the tissue of non-corpus luteum part. 3) The fluid cavity in the central part of corpus luteum for the non-pregnant cow or pregnant one is normal after breeding d60. The diameter of the cavity for pregnant cow is small than the non-pregnant one. The cavity fills with white tissue and disappeared gradually d60 after. 4) The features of corpus luteum color and internal and outside capillary system, and connective tissue and the protubrance are different for the early, middle and late pregnancy stages. It is possible to find out the pregnancy stages of ovary by morphology of corpus luteum. It will be more accurate based on the histology features as well. 5) The follicules number distribution on the surface of pregnant cow ovary are stable for all pregnancy period. On the average, over 20 follicles which 3=2 mm for each ovary. The small follicle accounts for 86.62% for total follicle number, which is main source of oocytes. After pregnant for 3 months, the number of big follicles are tend to decrease, and the follicle diameter tend to decrease too. 6) There is negative correlation between the big follicle and small follicle (PO.05). The number of middle follicle and small follicle are significant related with the pregnant day (PO.05). The number of middle follicle and small follicle are strongly correlated with number of oocyte, the grade of oocyte and indexs of IVP (PO.05). The ovary status and the reproductive physiological stages do not affect the number of follicle andfollicle distribution (P<0.05).From study of the histology and ultrastructure of corpus luteum for the all pregnancy period, the following conclusions were got: 1) there were the vacuole in LLC at the early stage of pregnancy, and the number gradually increased following the increase the the pregnant day. Most of LLC have the vacuole structure at 4 months pregnancy, and the vacuole are plenty and its diameter increase as well when pregnancy up to the 8 month. 2) The LLC apopotosis can be seen in some luteal cells at d35 of pregnancy, and all other sampling days following. The number increased greatly at d189, and luteal cells are obviously shown the regression. 3) It can be seen from the changes of corpus luteum ultrastructure, the cellular organelle of luteal cells are in the developmental stage, and the number increase stage. Between the pregnancy 2-5 month, the luteal cell structure well developed, and the cells are functional effective. The luteal cells show the obvious regression at 6 month pregnancy, and almost all celluar organella show the apopotosis clearly between the 7 month or 8 month.From study on the IVP for oocytes from the different pregnancy period, the following conclusion were got: 1) Under th...
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