No distinct stratification of ingesta particles and no distinct moisture gradient in the fore - stomach of non - ruminants : The wallaby , peccary , hippopotamus , and sloth

Herbivores that digest plant material in the fore-stomach can be divided in ruminants and non-ruminants. This study describes the distribution of feed particles (and inorganic material) and dry matter (DM) in the digestive tract of non-ruminant foregut fermenters. Results from passage trials led us to hypothesize that specific particle-sorting mechanisms, as observed in ruminants, are unlikely in non-ruminants. Therefore, no systematic particle size distribution effects (indicative of a sorting mechanism) should be evident in the fore-stomachs of these animals, but differences in fluid and particle retention suggest that differences in fluid concentration (measured as DM) could occur in the foregut of macropods and hippos. The gut content of eleven Bennett’s wallabies (Macropus rufogriseus), six collared peccaries (Pecari tajacu), three pygmy hippos (Hexaprotodon liberiensis), two common hippos (Hippopotamus amphibius) and one two-toed sloth (Choloepus didactylus) were analysed with an emphasis on the fore-stomach. The ventral and dorsal regions in sacciform compartments, and peripheral and central regions in tubular compartments, were examined. Results were not uniform across the species studied. A potential sedimentation mechanism was observed firstly by the accumulation of sand in the fore-stomach of the peccary and sloth, and secondly by the lower DM content in peripheral versus central and ventral versus dorsal regions of the fore-stomach of the wallabies and common hippos, respectively. However, pair-comparisons for different gut regions of wallabies and peccaries yielded no differences in mean particle size between fore-stomach regions. To conclude, some digesta fractionation does occur in the fore-stomach of the studied groups of non-ruminants, but not in a uniform manner, which in turn is in accordance with morphological dissimilarities of their respective foregut structures. The absence of systematic fractionation effects in non-ruminant foregut fermenters emphasizes the innovative character of the sorting mechanism in ruminants. DOI: https://doi.org/10.1016/j.mambio.2013.04.001 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-83989 Accepted Version Originally published at: Schwarm, Angela; Ortmann, Sylvia; Fritz, Julia; Flach, Edmund; Rietschel, Wolfram; Clauss, Marcus (2013). No distinct stratification of ingesta particles and no distinct moisture gradient in the fore-stomach of non-ruminants: The wallaby, peccary, hippopotamus, and sloth. Mammalian Biology Zeitschrift für Säugetierkunde, 78(6):412-421. DOI: https://doi.org/10.1016/j.mambio.2013.04.001