Photographs of a llama (Lama glama) stomach complex fixated in situ (with both the C1 and the C3 opened for access to the inside). Top: lateral right view (oesophagus pointing towards the right side of the picture), corresponding to the drawing in Fig. 2. Bottom left: dorsal view (oesophagus pointing towards the top of the picture). Bottom right: frontal view (oesophagus opening pointing towards the viewer). Note the relationships of the C2 to both the C1 and the C3 compartments. The C3 is located cranially, ventrally and caudally to the C2. The specimen did not originate from the present study but had been produced earlier by Urs Müller, preparator at the Institute of Veterainary Anatomy, Vetsuisse Faculty, University of Zurich

Photographs of a llama (Lama glama) stomach complex fixated in situ (with both the C1 and the C3 opened for access to the inside). Top: lateral right view (oesophagus pointing towards the right side of the picture), corresponding to the drawing in Fig. 2. Bottom left: dorsal view (oesophagus pointing towards the top of the picture). Bottom right: frontal view (oesophagus opening pointing towards the viewer). Note the relationships of the C2 to both the C1 and the C3 compartments. The C3 is located cranially, ventrally and caudally to the C2. The specimen did not originate from the present study but had been produced earlier by Urs Müller, preparator at the Institute of Veterainary Anatomy, Vetsuisse Faculty, University of Zurich

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Dust and grit are ingested by herbivores in their natural habitats along with the plants that represent their selected diet. Among the functions of the rumen, a washing of ingesta from adhering dust and grit has recently been demonstrated. The putative consequence is a less strenuous wear on ruminant teeth by external abrasives during rumination. T...

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... et al. 2019), and this washing mechanism has recently been demonstrated in goat and sheep (Hatt et al. 2019(Hatt et al. , 2020. Due to a series of similarities between ruminants and camelids, a similar washing mechanism is expected in the latter. The camelid forestomach is generally divided into three macroscopically distinct compartments (Fig. 1). Although some authors use the same terminology as in ruminants to describe these, this is not supported unanimously (reviewed by Langer 1988). Following , they are referred to as the voluminous C1 (the first compartment, the functional equivalent of the rumen), a small C2 (the second compartment, the functional equivalent of the ...
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... this is not supported unanimously (reviewed by Langer 1988). Following , they are referred to as the voluminous C1 (the first compartment, the functional equivalent of the rumen), a small C2 (the second compartment, the functional equivalent of the reticulum), and a tubular C3 (the third compartment). The proximal parts of the C3 (parts A-C in Fig. 1), also referred to as the 'gastric tube', are functionally similar to the ruminant omasum, but anatomically very different. The last part of the C3 (part D in Fig. 1) is lined by a glandular epithelium that corresponds to that of the abomasum. The camelid forestomach contains so-called glandular sacs in some areas of its C1 (Fig. 1). ...
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... of the rumen), a small C2 (the second compartment, the functional equivalent of the reticulum), and a tubular C3 (the third compartment). The proximal parts of the C3 (parts A-C in Fig. 1), also referred to as the 'gastric tube', are functionally similar to the ruminant omasum, but anatomically very different. The last part of the C3 (part D in Fig. 1) is lined by a glandular epithelium that corresponds to that of the abomasum. The camelid forestomach contains so-called glandular sacs in some areas of its C1 (Fig. 1). The openings between the C1 and C2, and between the C2 and C3, are of smaller magnitudes than the openings between rumen and reticulum, or between reticulum and ...
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... (parts A-C in Fig. 1), also referred to as the 'gastric tube', are functionally similar to the ruminant omasum, but anatomically very different. The last part of the C3 (part D in Fig. 1) is lined by a glandular epithelium that corresponds to that of the abomasum. The camelid forestomach contains so-called glandular sacs in some areas of its C1 (Fig. 1). The openings between the C1 and C2, and between the C2 and C3, are of smaller magnitudes than the openings between rumen and reticulum, or between reticulum and omasum, in ruminants of similar body size ( Pérez et al. 2016), which might be linked to the generally lower food intake in camelids ( Dittmann et al. ...
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... (Hatt et al. 2019(Hatt et al. , 2020) could be demonstrated in camelids. One of the methods used was computed tomography (CT). Because previous descriptions of the camelid forestomach with CT images (Van Hoogmoed et al. 1998; Stieger-Vanegas and Cebra 2013) deviate in their identification of the C2 from anatomical displays of fixated specimens (Fig. 1), photographs ( Pérez et al. 2016) or schematic drawings ( ; Fig. 2), special attention was directed towards the identification of the C2 in CT images. ...
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... were converted to DICOM medical imaging format and evaluated in Horos v3.3.6 (Horos Project 2019). Radiodense silica volumes (cm 3 ) were calculated by manually defining regions of interest (ROIs) on every sixth slice and automated interpolation of missing ROIs. To guide the interpretation of the CT images, please refer to the fixated specimen in Fig. 1 and the schematic visualisation of the camelid stomach in Fig. 2. Note that the specimen from which the fixated stomach was produced was not part of the present study, but an approximately 8-year-old female llama euthanized for medical reasons unrelated to the gastrointestinal tract several years ...
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... not sharing a letter are signifi The camelid forestomach was previously depicted by CT by Van Hoogmoed et al. (1998) andStieger-Vanegas andCebra (2013). In both studies, the label 'C2' was allocated to a structure that was most cranial, and in the case of the latter study, even on the left side of the stomach complex (Fig. 3 of the former and Fig. 1C of the latter publication). To our opinion, that structure corresponds to the cranial C3 or the ventral C1; the C2, by contrast, is located on the right side of the camelid stomach complex, and, in contrast to its analogue, the ruminants' reticulum, is not the most cranial structure of the complex (Figs. 1, 2, 3). In these studies, ...
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... both studies, the label 'C2' was allocated to a structure that was most cranial, and in the case of the latter study, even on the left side of the stomach complex (Fig. 3 of the former and Fig. 1C of the latter publication). To our opinion, that structure corresponds to the cranial C3 or the ventral C1; the C2, by contrast, is located on the right side of the camelid stomach complex, and, in contrast to its analogue, the ruminants' reticulum, is not the most cranial structure of the complex (Figs. 1, 2, 3). In these studies, contrast materials were applied to the animals. ...
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... This study was part of the AgroVet cooperation between Strickhof Eschikon and the Vetsuisse Faculty of the University of Zurich. We thank Anja Tschudin for support in pelleted diet formulation, Hanspeter Renfer for support in animal husbandry, Michelle Aimée Oesch for the photographs and Urs Müller for the production of the specimen displayed as Fig. 1, and Emilia Clauss for the drawing of Fig. ...

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... In addition to this comparative sample, we collected food and digesta from ruminally cannulated Holstein dairy cows. Such animals are ideal for testing the extent to which rumen fluid 'washes' exogenous silica from food surfaces (Hatt et al., 2019(Hatt et al., , 2021. Our aim in producing these complementary datasets is twofold: first, we describe and validate a protocol for differentiating and quantifying silica in the diets of mammalian herbivores; and second, we report pilot findings to highlight the practical value and future promise of this approach. ...
... Values averaged from two cannulated cows (see Figure S2 for individual values). Illustration by William Scavone of goats, sheep and llamas, all ruminants, found excess accumulations of exogenous grit in the posterior chambers of the stomach, suggesting that some fraction of it was 'washed' from food surfaces before regurgitation and remastication (Hatt et al., 2019(Hatt et al., , 2021. Such washing could explain why non-ruminant equids (horses) express greater hypsodonty than ruminants with similar diets (Damuth & Janis, 2011); they probably encounter more exogenous grit per bolus (Dittmann et al., 2017). ...
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Silica is crucial to terrestrial plant life and geochemical cycling on Earth. It is also implicated in the evolution of mammalian teeth, but there is debate over which type of siliceous particle has exerted the strongest selective pressure on tooth morphology. Debate revolves around the amorphous silica bodies (phytoliths) present in plants and the various forms of siliceous grit—that is, crystalline quartz (sand, soil, dust)—on plant surfaces. The problem is that conventional measures of silica often quantify both particle types simultaneously. Here we describe a protocol that relies on heavy‐liquid flotation to separate and quantify siliceous particulate matter in the diets of herbivores. The method is reproducible and well suited to detecting species‐ or population‐level differences in silica ingestion. In addition, we detected meaningful variation within the digestive tracts of cows, an outcome that supports the premise of ruminal fluid ‘washing’ of siliceous grit. We used bootstrap resampling to estimate the sample sizes needed to compare species, populations or individuals in space and time. We found that a minimum sample of 12 individuals is necessary if the species is a browser or as many as 55 if the species is a grazer, which are more variable. But a sample size of 20 is adequate for detecting statistical differences. We conclude by suggesting that our protocol for differentiating and quantifying silica holds promise for testing competing hypotheses on the evolution of dental traits.
... The main exception is ruminating foregut fermenters (taxonomic ruminants and camelids). Due to the density and fluid-dependent sorting mechanism in their forestomachs, sand is washed off the digesta prior to regurgitation for rumination and accumulates without clinical consequences in a part of the stomach complex before being excreted (Hatt et al., 2019;Hatt et al., 2020;Hatt et al., 2021). In non-ruminant foregut fermenters like hippopotamus, sloths or peccaries, the accumulation of sand in certain, sometimes dead-end structures of the forestomach, without apparent clinical problems, has also been reported (Schwarm et al., 2010;Schwarm et al., 2013;Wings et al., 2008). ...
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We determined location and amount of accumulated sand in the gastrointestinal tract (GIT) of rabbits (Oryctolagus cuniculus) and guinea pigs (Cavia porcellus) fed diets containing external (silicate) abrasives. Computed tomographic abdominal images of rabbits (n=44) and guinea pigs (n=16) that each received varying numbers (4-7) of different diets for 14 days each (total n=311 CTs), and radiographs of dissected GIT and presence of silica in GIT content (n=46 animals) were evaluated. In rabbits, the majority of accumulated sand was located in the caecal appendix, an elongated, intestinal structure in the left side of the abdomen. The ‘wash-back’ colonic separation mechanism in rabbits may be partly responsible for a retrograde transport of sand back to the caecum, where dense, small particles accumulate in the appendix. The appendix likely acted as a reservoir of these particles, leading to significant effects not only of the momentary but also of the previous diet on recorded sand volumes in the rabbits. Guinea pigs have no caecal appendix and a colonic separation mechanism not based on a ‘wash-back’. Less sand accumulation was found in their GIT without a specific location pattern, and there were less previous diet effects in this species. None of the rabbits or guinea pigs developed clinical signs of obstruction during the study, and the recorded sand volumes represented 1.0 ±1.2% of the 14-d sand intake in rabbits and 0.2 ±0.2% in guinea pigs. Accumulation of sand in volumes up to 10 cm³ in the gastrointestinal tract of rabbits does not seem to cause clinical health impairment. Large inter-individual differences in rabbits indicate inter-individual variation in proneness to sand accumulation. The reason for the presence of a sand-trapping caecal appendix in animals that are, due to their burrowing lifestyle and feeding close to the ground, predestined for accidental sand ingestion, remain to be unveiled.
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Objectives: Colobines are a group of foregut-fermenting AfroEurasian monkeys that includes more than 70 species grouped into 10 genera which are widely distributed throughout Asia and Africa. Colobines are classified as tripartite or quadripartite based on the number of compartments in their stomach. To expand our understanding of their morphophysiological digestive characteristics, we attempted to visualize their stomach using photographs, examine the ontogenetic development of gastrointestinal size, and evaluate the interspecific differences in gastrointestinal size relative to the body size with a special reference to differences in stomach types. Materials and Methods: Gastrointestinal tracts were dissected from 144 deceased colobine specimens in the Japan Monkey Centre stored in formalin. We measured the gastrointestinal tracts of nine species with a tripartite stomach and two species with a quadripartite stomach. We used an allometric linear regression model to establish how body mass was related to stomach weights and all intestine lengths. Results and discussion: Our results support previous findings about primate and colobine macroscopic digestive tracts. In particular, we document the small size of the openings connecting stomach compartments and found that it may be difficult to differentiate between a bulging haustrated pouch and a real praesaccus. The stomach mass analyses indicated hyperallometric stomach growth in colobine infants as opposed to isometric scaling in juvenile specimens and hypoallometric scaling in mature specimens, which is similar to findings in other foregut fermenters. Stomach weight was greater in species with quadripartite stomachs than in species with tripartite stomachs, which suggests that species with a quadripartite stomach possibly have a larger stomach capacity, supporting the concept of their evolutionary adaptation to folivory.