Histomorphometric and immunohistochemical study of the goat reticulum during prenatal development.

This study sought to describe the morphological changes taking place in the goat reticulum during prenatal development, using histomorphometric and immunohistochemical techniques. A total of 140 goat embryos and foetuses were used, from the first stages of prenatal life until birth. Differentiation of the reticulum as a separate compartment of the primitive gastric tube was observed at 35 days of prenatal life (23% gestation). By 38 days (25% gestation) the reticular wall comprised three layers: an internal epithelial layer, a middle layer of pluripotential blastemic tissue and an external layer or serosa. Primary reticular crests were visible at 59 days (38% gestation) as evaginations of the epithelial stratum basale, marking the earliest histological differentiation of future reticular cells. Secondary reticular crests were observed at 87 days (61% gestation). Corneum papillae first became apparent on the lateral surface of primary reticular crests at 101 days (64% gestation). The muscularis mucosae was visible by 101 days (64% gestation) in primary reticular crests. Neuroendocrine cells were detected by synaptophysin at 64 days (43% gestation), while glial cell markers (glial fibrillary acidic protein and vimentin) were observed at 64 days (43% gestation) and 38 days (25% gestation), respectively. The peptidergic innervation markers such as neuropeptide Y and vasoactive intestinal polypeptide were detected at 75 days (50% gestation). In conclusion, prenatal development of the reticulum - like that of the rumen - appears to take place somewhat earlier in goats than in sheep or cattle, but at a similar rate to that reported in deer.