Histomorphometric and immunohistochemical study of the goat omasum during prenatal development

This work studies the morphological changes taking place in the goat omasum during prenatal development, using scanning electron microscope, light microscopy and immunohistochemical analysis. A total of 140 goat embryos and fetuses were used, from the first stages of prenatal life until birth. Differentiation of the omasum as a separate compartment of the primitive gastric tube was observed at 35 days of prenatal life ([crown-rump length (CRL)] 3 cm, 23% gestation). By 38 days (CRL 4.3 cm, 25% gestation) the omasal wall comprised three layers: an internal epithelial layer, a middle layer of pluripotential blastemic tissue and an external layer or serosa. Omasal laminae appeared in the following order: primary at 38 days (CRL 4.3 cm, 25% gestation), secondary at 50 days (CRL 7.7 cm, 33% gestation), tertiary at 59 days (CRL 12 cm, 39% gestation) and quaternary at 64 days (CRL 13.5 cm, 43% gestation). Neuroendocrine cells were detected by synaptophysin (SYP) at 52 days (CRL 8 cm, 35% gestation), while glial cell markers (glial fibrillary acidic protein - GFAP, and vimentin-VIM) were observed at 64 days (CRL 13.5 cm, 43% gestation) and 38 days (CRL 4.3 cm, 25% gestation), respectively. Sympathetic and parasympathetic nerve fibers and nerve bodies were detected via neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP) at 95 days (CRL 20 cm, 63% gestation). In conclusion, prenatal development of the omasum - like that of the rumen - appears to take place somewhat earlier in goats than in sheep or cattle, but at a similar stage to that reported in deer.