Blue duikers and red duikers have very similar rumen anatomy. In both species the rumen is a simple, plesiomorphic, sacculated S-shaped tube, while the ostia are large and the ruminal pillars weak. These specialisations facilitate rapid digesta passage. The rumens are densely papillated, and the fungiform papillae are highly vascular to aid absorption. Many of the adaptations are characteristic of concentrate selectors. Total concentrations of numeral fatty acids are lower in the red duiker than the blue duiker. Propionic and butyric acid concentrations are higher in the blue duiker than the red duiker while acetic acid concentration are greater in red duikers. Caecal concentrations of volatile fatty acids (especially acetic acid) are greater than those in the rumen of the blue duiker, but likely contribute less energy to metabolism because of the small size of the caecum relative to that of the rumen
