On day 33, intestinal sections (duodenum, jejunum, and ileum) were collected from five birds from each group and flushed with 0.9% saline solution, then preserved, and fixed for 48 h in neutral buffered 10% formalin [19 (link)]. A rotatory microtome was used to prepare 3–4 μm paraffin wax sections, which were deparaffinized, stained with haematoxylin and eosin (H&E), and examined under a light microscope [20 ]. The histomorphometry of villus height and crypt depth was implemented by a high-power lens (X 400). Histomorphometry was done through a computerized microscopic image analyser linked to a full HD microscopic camera (Leica Microsystems, Germany).