Adaptive Anatomical Specialization of the Intestines of Alpacas Taking into Account their Original Habitat and Feeding Behaviour

Abstract

The gastrointestinal tract of the alpaca (Vicugna pacos) is most efficiently adapted to its habitat at high altitudes. Alpacas, just like ruminants, feed on hardly digestible forage. However, it has been demonstrated that the anatomy of the camelid digestive tract has developed independently of ruminants and not in homology to them. Despite a long history of domestication and an increasing number of animals worldwide, little research has been done on the intestinal anatomy of alpacas. The purpose of this study was to describe the anatomical features of the alpaca's intestines and to explain anatomical peculiarities in the context of evolutionary function and morphology. Another goal of this study was the demonstration of weaknesses of the intestinal anatomy predisposing alpacas to certain clinical presentations. Six animals were used for dissection. The basic structure of the intestines was comparable to that in ruminants. However, a number of characteristic peculiarities were found in alpacas, like the duodenal ampulla and the proximal and distal loop of the ascending colon. The jejunum and ileum, unlike those of ruminants, had their own mesentery largely separated from the ascending mesocolon. The main blood supply was provided by the cranial and caudal mesenteric artery. The particular lymph nodes were located along the branches of these two arteries. The spiral colon seemed to play a major role in intestinal digestion and water resorption. The size of the distal fermentation chamber allows the presumption that alpacas belong to the group of animals practicing a fractionated fermentation in the proximal and distal fermentation chambers. Anat Rec, 301:1840–1851, 2018. © 2018 Wiley Periodicals, Inc.