Comparative analysis of the merino sheep and Iberian red deer abomasum during prenatal development.

The aim of this study is to describe differences in the ontogenesis of the abomasum in sheep (domestic ruminant) and deer (wild ruminant). Histomorphometric and immunohistochemical analysis were carried out on 50 embryos and fetuses of the sheep and 50 red deer from the first prenatal stages until birth. To compare similar periods of gestation in both species, we calculate the percentages of gestation. The appearance of the abomasum was earlier in the red deer (22% gestation) than in the sheep (25% gestation). Throughout development the epithelium happened sequentially, being of the types pseudostratified to simple cylindrical. This important modification was earlier in the red deer than the sheep. At 46% gestation in red deer and 50% in sheep, gastric pits were observed on the surface of abomasal folds. Our studies suggest a close link between the initial formation of these pseudoglandular structures and the clear separation of lamina propria and submucosa separated by de muscularis mucosae. At 54% gestation in red deer and at 60% in sheep, in the bottom of these pits the first outlines of glands were distinguishable. Finally, the presence of neuroendocrine and glial cells were detected in deer at earlier stages than in sheep.