The oviduct in chaos

Abstract

Listen

Translate article

The unilateral avian oviduct is divisible into five functional regions which, moving distally, include the infundibulum, magnum, isthmus, tubular shell gland and shell gland pouch. Each region subserves a variety of functions, which through their interaction give rise to the multilayered albumen, shell membranes and the organic/inorganic complex, which comprises the shell. The sequential activity of these structurally diverse regions is a necessary prerequisite for “normal” egg formation. The reproductive effort can be influenced by a number of disease processes either directly by virtue of the fact that they alter the ability of the lining cells to synthesise their integral components or indirect by generally compromising bird health. Notable amongst the former are Infectious Bronchitis, Newcastle Disease and Egg Drop Syndrome. All change the quality of the final product in terms of the shape and texture of the shell. In recent years it has become evident that environmental stress has an equally, if not more, important role to play in oviduct disfunction. In the absence of large areas of functional surface epithelium, the eggs laid were structurally defective at all levels from the mammillary layer outwards. As the epithelial layers regenerated, shell quality approximated normality, but never returned to the pre-stress condition.The process of candling signals amongst other internal defects a variety of inclusions variously classified as blood and meat spots. They are quite specific in their locations; thus blood spots originating from the rupture of ovarian blood vessels at ovulation, are invariably confined to the periphery of the yolk mass, while meat spots now classified according to their composition are confined to albumen. Within the latter they are recognised as tissue rich deposits, the result of oviduct breakdown and/or calcium rich fragments. The latter implies a breach in the barrier provided by the soft shell membranes.