Digestion

With their elongated upper lip and nose, known as the trunk, elephants are able to grasp food items using their trunk while feeding. Food is transferred to the mouth where large molars grind down the plant matter. The grinding teeth do not succeed each other vertically, but instead move forward as the the foremost tooth wears down and falls out (Ullrey et al., 1997).  When the grinding teeth are pushed out, they are broken down into transverse plates producing a surface that is important for reducing woody foods into a digestible size (Ullrey et al., 1997).

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Chewed food mixed with saliva passes down to the esophagus, then to the to stomach, which is connected to the small intestine, where it then moves into the colon (Ullrey et al., 1997). The colon is a segmented organ in which the majority of digesta is located in the proximal two-thirds (Ullrey et al., 1997).  About two-thirds to three-quarters of wet digest can be found  in the cecum and colon, where microbial fermentation is most prominent (Ullrey et al., 1997). 

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Digestion of proteins begins in the stomach where fat and carbohydrates are moved into the small intestine and broken down into absorbable forms (Ullrey et al., 1997). The cecum and colon are made up of anaerobic bacteria and protozoa that digest plant fibers (cellulose and hemicellulose) that are typically difficult to digest (Ullrey et al., 1997). These microorganisms are also found in the small intestine and duodenum, however concentration are lowest there and increase as they approach the distal jejunum and ileum (Ullrey et al., 1997). 

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(Clauss et al. (2006) dives further into the comparative morphology between Asian and African elephants to better understand retention times and digestion coefficients between the two species. The authors hypothesized a longer intestinal tract within the Asian elephants, allowing them for more foraging of grass. 

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The digestive tract of African elephants is relatively short compared to most herbivorous animals (Clauss et al., 2006). Elephants differ in their physiology  from other hooved species due to their short ingesta retention times and low digestion rates (Clauss et al., 2006). According to Clauss et al. (2006), the large intestine was barely larger than the small intestine, setting them apart from other herbivores. Since grass contains longer fermentative energy at a slower rate, longer ingesta retention times have been observed as a result of an adaption of herbivores consuming grass (Clauss et al., 2006).

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Grass is a flexible material that does not break easily; it requires a higher degree of enamel folding which the African elephants do not have (Clauss et al., 2006). In comparison, Asian elephants have more ridges in their molar structure, allowing them to possess a greater adaptation for grass forage (Clauss et al., 2006). Observations in the differences of ingesta retention and digestive efficiency between the species have been noted in the gastrointestinal morphology (Clauss et al., 2006). 

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