Developmental stages and growth of the proventriculus of post-hatching Muscovy duck: Light and electron microscopic study

Abstract

The present study was implemented to provide comprehensive information on the developmental sequence of the proventriculus of Muscovy ducks by gross examination, macro-micrometric analysis and by using light microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM). Samples from 55 healthy post-hatching Muscovy ducks of both sexes ranging from 1 to 60 days old. The proventriculus began cranially opposite to the cranial end of the liver at 1-15 days old, but in front this level at 30 and 60 days old. Morphometrically, the length of the proventriculus was increased by about four folds while weight by 19 folds at 60 days old when compared with those at one day old. Scanning electron microscopy of the proventricular lumen at one day old exhibited numerous small mostly rounded irregularly distributed openings of the glands, but uniformly distributed and surrounded by closely packed concentrically arranged mucosal folds resembling a rosette shape at the older ages. Histologically, in all studied stages, rounded, elongated oval or polymorphic shaped lobules of the proventricular glands were occupied within the muscularis mucosa. The tubuloalveolar secretory units lined with secretory (oxyntico-peptic) cells with variable shapes had secretory granules increased by the development. Numerous argyrophilic endocrine cells were demonstrated away from the glandular lumen at older ages. Transmission electron microscopy revealed that the cytoplasm of the secretory cells contained homogeneously electron-dense granules at a young age, but two types of these granules could be recognized at 60 days old. In conclusion, this study provides a wide difference in the morphometric and the structure of the proventriculus from one day to 60 days old. This difference between the examined age-stages may be related to the feeding strategy (behavior) and the functional adaptations from the young to the older ages.

Keywords: SEM; argyrophilic endocrine cells; ducks; oxyntico-peptic cells; proventriculus.