119 EARLY BOVINE GESTATIONAL DEVELOPMENT: MANIPULATED (IVF) AND NOT MANIPULATED IN LABORATORY

Abstract

High embryonic and fetal death rates in manipulated embryos in laboratory suggest that the process of early placentation can be inefficient. This investigation aimed to evaluate the development of placenta, and organogenesis of Nelore bovine embryos, and fetuses by natural stud and in vitro fertilization (IVF) over the period from 15 to 70 days of pregnancy. Fifty-nine embryos (15 to 50 days of gestation), 9 fetuses in initial period (60 to 70 days of gestation), and 10 embryos originated by IVF technique (35 to 46 days of gestation) were used. The same semen was used for all IVF, except the embryos originated by natural stud. The embryos were prepared by serial sections and the fetal membranes were fixed in 4% paraformaldehyde for light and scanning electron microscopy (SEM) and 2.5% glutaraldehyde for transmission electron microscopy (TEM). All material was routinely processed and stained. The embryos and fetuses originating from natural stud showed an increase in growth based on the weight of the gestational sac, and related with cranio-caudal and dorso-ventral length of the chorioallantois and amniotic membrane in periods from 20 to 30 and from 50 to 60 days of the pregnancy. The gross appearance of the first cotyledons in development (9.39 ± 0.73 cm) was quantified at 30 to 40 days of pregnancy. The IVF embryos on days 35 to 46 of gestation showed discreet cotyledons presenting a functional decrease of development related to embryo derived naturally. Ultrastructurally, the trophoblast showed binucleate trophoblast giant cells with a cytoplasm rich in electrodense vesicles and few mitochondria located in the apical poles suggesting lower cell activity. The yolk sacs of IVF embryos were shorter (1.07 ± 0.55 cm) when compared with the natural group (5.53 ± 3.14 cm) over 30 to 40 days of pregnancy. In both groups, the epithelium of the yolk sac presented cells with round nuclei, hemangioblast cells, and blood islands with a great number of primitive mononuclear cells. Embryos by natural stud (10% of analyzed ones) showed malformations in cephalic and frontal curvature, encephalocele, gastroschisis, and hepatomegaly. In conclusion, these results indicate occurrence of alteration in the organogenesis in bovine embryos originated by natural stud and retardation of fetal membrane development in bovine embryos by IVF.

This work was supported by FAPESP and CAPES.