Digesta retention patterns of solute and different‑sized particles in camelids compared with ruminants and other foregut fermenters

The mean retention times (MRT) of solute or particles in the gastrointestinal tract and the forestomach (FS) are crucial determinants of digestive physiology in herbivores. Besides ruminants, camelids are the only herbi- vores that have evolved rumination as an obligatory physi- ological process consisting of repeated mastication of large food particles, which requires a particle sorting mechanism in the FS. Differences between camelids and ruminants have hardly been investigated so far. In this study we meas- ured MRTs of solute and differently sized particles (2, 10, and 20 mm) and the ratio of large-to-small particle MRT, i.e. the selectivity factors (SF10/2mm, SF20/2mm, SF20/10mm), in three camelid species: alpacas (Vicugna pacos), llamas (Llama glama), and Bactrian camels (Camelus bactrianus). The camelid data were compared with literature data from ruminants and non-ruminant foregut fermenters (NRFF). Camelids and ruminants both had higher SF 10/2mm FS than NRFF, suggesting convergence in the function of the FS