Integrated Morphological Analysis Of The Small Intestine In The Pekin Duck's (Anas platyrhynchos) Using Gross Anatomical, Histological, Histochemical, and Scanning Electron Microscopic Techniques.

The adult White Pekin duck's small intestine is anatomically adapted for rapid growth, high-fat diet digestion, and strong immunity, essential for its physiological needs. This study analyzes the adaptive anatomical features of the small intestine-duodenum, jejunum, and ileum-through gross examination, light microscopy (LM), histochemical techniques, scanning electron microscopy (SEM), and morphometric analysis. To achieve this objective, sixteen ducks were examined. Gross examination revealed a U-shaped duodenum, a coiled jejunum with Meckel's diverticulum, and a straight ileum attached to paired ceca. Histologically, the duodenum displayed finger-like villi with the deepest crypts, while the jejunum had the tallest villi and the highest villus/crypt ratio. The ileum showed compact villi and the highest goblet cell (GC) density. GCs were quantified and differentiated using PAS, AB, and PAS-AB combination staining. PAS-positive (neutral mucins) cells predominated in villi, especially in the jejunum, while AB-positive (acidic mucins) cells were most abundant in ileal crypts, indicating regional specialization in mucosal protection. SEM revealed ultrastructural features including dense microvilli, epithelial exfoliation, and GC secretory vesicles. Enterocytes exhibited organelles such as mitochondria and rough endoplasmic reticulum, as well as junctional complexes including tight junctions and desmosomes. These findings highlight the segmental specialization of the Pekin duck's small intestine, with the jejunum optimized for nutrient absorption and the ileum for immune defense. The detailed mucin profile and ultrastructural features provide insight into the digestive efficiency and adaptive physiology of this fast-growing avian species.