Preliminary evidence for a forestomach washing mechanism in llamas (Lama glama)

Jean-Michel Hatt,Daryl Codron,Henning Richter,Patrick R Kircher,Jürgen Hummel,Marcus Clauss

doi:10.1007/s42991-021-00142-1

Jean-Michel Hatt, Daryl Codron + Show 4 more

Open Access

https://doi.org/10.1007/s42991-021-00142-1

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Abstract

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. The same function should theoretically apply to camelids, but has not been investigated so far. We fed six llamas (Lama glama) a diet of grass hay and a lucerne-based pelleted food in which fine sand had been included at about 8% of ingredients, for ad libitum consumption for 6 weeks. Subsequently, animals were slaughtered and content of the different sections of the gastrointestinal tract was sampled for the analysis of dry matter (DM), total ash, and acid detergent insoluble ash (ADIA, a measure for silica). Additionally, two of the animals were subjected to whole-body computer tomography (CT) after death in the natural sternal resting position. No clinical problems or macroscopic changes in the faeces were observed during the experimental period. The results indicate an accumulation of ADIA in the C3 compartment of the stomach complex, in particular in the posterior portion that is the equivalent of the abomasum in ruminants. By contrast, contents of the C1, from which material is recruited for regurgitation and rumination, were depleted of ADIA, indicating that the contents had largely been washed free of sand. The washing effect is an unavoidable side effect of the flotation- and sedimentation-based sorting mechanisms in the ruminant and the camelid forestomachs. In theory, this should allow ruminants and camelids to live in similar habitats as nonruminant herbivores at lower degrees of hypsodonty.

Highlights

Many mammals inadvertently ingest relevant amounts of indigestible material with their natural diet, including dust, grit, sand and soil
Even though sand impaction is sporadically reported as a health problem in domestic animals, especially in horses (Hassel et al 2020), the general perception is that the mammalian digestive tract can handle ingested soil quite well (Dirksen 2002; Husted et al 2005; Kendall et al 2008; Siwińska et al 2019)
The present study underlines the functional similarities between the ruminant and camelid digestive tracts and reveals preliminary evidence for the presence of a forestomach washing mechanism in camelids. We consider this a pilot study, because the results are based on only six animals; because food intake could not be controlled completely, with animals ingesting unknown proportions of sand-containing pelleted food, grass hay, and pasture grass; and because the period the animals were under observation was comparatively short at 6 weeks

Summary

Introduction

Many mammals inadvertently ingest relevant amounts of indigestible material with their natural diet, including dust, grit, sand and soil. This is observed in insectivorous and especially myrmecophagous mammals (McNab 1984; Gull et al 2015), but in herbivores (Skipworth 1974; Arthur and Alldredge 1979; Arthur and Gates 1988; Beyer et al 1994; Hummel et al 2011; Turner et al 2013; Sanson et al 2017). Even though sand impaction is sporadically reported as a health problem in domestic animals, especially in horses (Hassel et al 2020), the general perception is that the mammalian digestive tract can handle ingested soil quite well (Dirksen 2002; Husted et al 2005; Kendall et al 2008; Siwińska et al 2019).

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