The study was conducted to describe the histology, morphometry and morphology of the papillae on the ventral sac of the rumen of neonatal dairy calves using light, digital and scanning electron microscopy. Sixteen two-week old Holstein Friesian-Sahiwal cross calves were divided into four groups then fed with different diets for 60 days. The diets were T1 (milk replacer), T2 (milk replacer and fresh Napier grass), T3 (milk replacer and concentrate) and T4 (milk replacer, fresh Napier grass and concentrate). The epithelium was thinnest (7.8±1.67 µm) (P<0.05) and thickest (15.6±3.9 µm) (P<0.05) in T3 and T2, respectively. The lamina muscularis was thinnest (71.7±20.67 µm) (P<0.05) and thickest (175.1±15.43 µm) (P<0.05) in T1 and T2, respectively. Papillae were shortest (35.7±3.47 µm) (P<0.05) and longest (214.8± 37.79 µm) (P<0.05) in T1 and T4, respectively. All the treatments reacted to Periodic Acid-Schiff and Alcian blue pH 1.0 and pH 2.5 stains. Finger-like and tongue-shaped papillae were the predominant papillae observed. Complex branching of papillae were seen only in T4. The study showed that there were signifcant differences in the anatomical features of the papillae in calves fed with different diets.