Gross Measurements of the Digestive Tract and Visceral Organs of Addax Antelope (Addax nasomaculatus ) Following a Concentrate or Forage Feeding Regime

Abstract

Differences in macroscopic measurements of the gastrointestinal tract have been hypothesized to correlate with the browser-grazer continuum in the natural diet of ruminants. However, to what extent these characteristics represent species-specific traits, or respond to the actually ingested diet, remains to be investigated. Twelve surplus addax antelope (Addax nasomaculatus) were divided into two groups and fed, for 3 months, either their usual diet, consisting of a concentrate feed with a limited amount of hay, or a diet of unlimited hay only. After culling, macroscopic measurements were compared between groups. The macroscopic anatomy of the addax showed many characteristics considered typical for grazing or 'cattle-type' ruminants. While both diet groups had mesenteric, pericardial and perirenal adipose tissue, these depots were subjectively more pronounced in concentrate-fed animals. Hay-fed animals had significantly heavier filled forestomach compartments, with corresponding significantly longer linear measurements. Masseter muscles and the surface of first-order omasal leaves were significantly more prominent in hay-fed animals, reflecting possible adaptations to overcome resistance of grass forage and to reabsorb fluid from increased rumination, but differences were not as distinct as reported between 'cattle-type' and 'moose-type' ruminants. Some measurements such as reticular crests and empty foregut mass remained stable between groups, indicating possibly genetically pre-defined characteristics less prone to change in adult life. The results emphasize the adaptability of ruminant digestive tract anatomy in adult animals even after a short period of time, but also suggest limits to this adaptability that reveals a species-specific anatomy regardless of the diet actually consumed.

Effect of pelleted cereal-based feed for addax antelope (<i>Addax nasomaculatus</i>) on feed intake and nutrient digestibility

“…Addax is classified as a typical grazer or grazer with minor amount of browse in the natural diet (Gagnon and Chew, 2000) and with anatomical and physiological characteristics considered typical for grazing ruminants (Hummel et al, 2008;Clauss et al, 2009;Tahas et al, 2017). This desert antelope living in Sahara is adapted to a low quality forage (high in fibre) and limited access to water by high particulate and fluid retention times in the rumen (Hummel et al, 2008).…”

“…This desert antelope living in Sahara is adapted to a low quality forage (high in fibre) and limited access to water by high particulate and fluid retention times in the rumen (Hummel et al, 2008). Although in the wild the addax forages predominantly on coarse and bulky roughages, in captivity often a high proportion of unstructured feeds can be found in the diet for this species (Schilcher et al, 2013), even though it is possible to maintain addax for a long time on a roughage-only diet (Tahas et al, 2017). In the current study, unstructured feed intake (mainly concentrates) ranged from 47 to 52% of the consumed DM.…”

Comparative omasum anatomy in ruminants: Relationships with natural diet, digestive physiology, and general considerations on allometric investigations

“…Anatomical measurements were either taken from existing publications (Bonin, Tremblay, & Côté, ; Booyse & Dehority, ; Church, ; Clauss, Hofmann, Hummel, et al, ; Clauss, Hummel, Vercammen, & Streich, ; Clauss, Hummel, Völlm, Lorenz, & Hofmann, ; Clauss, Reese, & Eulenberger, ; Geiger, Hofmann, & König, ; Hofmann, ; Hofmann, Geiger, & König, ; Hofmann, Knight, & Skinner, ; Holand & Staaland, ; Holtenius & Björnhag, ; Jerbi, Bayoudh, Clauss, & Pérez, ; Jerbi & Pérez, ; Jiang et al, ; Lauwers, ; Ledger & Smith, ; Li, Yuan, & Zhou, ; Mathiesen et al, ; McSweeney, ; Nagy & Regelin, ; Pérez, Erdogan, & Ungerfeld, ; Pérez & Ungerfeld, ; Pérez & Vazquez, ; Pfeiffer, ; Reissig, ; Sauer et al, ; Sauer et al, ; Sauer, Bertelsen, Lund, Weisbjerg, & Clauss, ; Sibbald & Milne, ; Staaland, Adamczewski, & Gunn, ; Stafford & Stafford, ; Tahas et al, ; Takatsuki, ; Werner, ), or from previously unpublished observations during dissections performed by both senior authors. The data are given in the electronic Supporting Information.…”

“…This introduces certain subjectivity in the number of second and higher order leaves. This system was generally used by the main data collector of the present study (Hofmann, , , ), the senior author (Clauss, Hummel, Völlm, et al, ; Clauss, Reese, & Eulenberger, ), and in work supervised by them (Sauer et al, ; Sauer, Bertelsen, Hammer, et al, ; Sauer, Bertelsen, Lund, et al, ; Tahas et al, ; Werner, ). All data referring to the number of first and second order leaves in the present study were derived in this way.…”

“…The selectivity factor in the reticulorumen (SF RR) is the ratio of small particle to fluid retention times, with higher values indicating a higher fluid throughput relative to particle retention (Dittmann, Hummel, et al, ). It is typically positively (but not linearly) related to %grass, where species above a threshold of about 20% grass in the natural diet have higher SF RR (Dittmann, Hummel, et al, ), and is negatively related to the intraruminal papillation gradient (Tahas et al, ). The blackbuck ( Antilope cervicapra ) has been described as an outlier in terms of omasum anatomy, with a high SF RR yet an unexpectedly small omasum (Hummel et al, ; Sauer, Bertelsen, Hammer, et al, ).…”