Fluid and particle retention in the digestive tract of the addax antelope (Addax nasomaculatus)—Adaptations of a grazing desert ruminant

Abstract

Retention time of food in the digestive tract is a major aspect describing the digestive physiology of herbivores. Differences in feed retention times have been described for different ruminant feeding types. In this study, a dominantly grazing desert ruminant, the addax (Addax nasomaculatus), was investigated in this respect. Eight animals with a body weight (BW) of 87+/-5.3 kg on an ad libitum grass hay (Chloris gayana) diet were available. Co-EDTA and Cr-mordanted fibers (<2 mm) were used as pulse-dose markers. Mean retention time (MRT) in the digestive tract was calculated from faecal marker excretion. Average daily intake of the addax was found to be 1.7 kg dry matter (DM) or 60+/-8.3 g DM/kg BW(0.75). The MRT of fluid and particles in the reticulo-rumen (MRT(fluid)RR and MRT(particle)RR) were quantified to be 20+/-5.8 and 42+/-7.0 h respectively. When compared to literature data, MRT(fluid)RR was significantly longer than in cattle species, and MRT(particle)RR was significantly longer than in 11 taxa of all feeding types. The ratio of MRT(particle)RR/MRT(fluid)RR (2.3+/-0.5) was found to be within the range described for grazing ruminants. The long retention times found in the addax can be interpreted as an adaptation to a diet including a high proportion of slow fermenting grasses, while the long retention time of the fluid phase can be interpreted as a consequence of water saving mechanisms of the desert-adapted addax with a potentially low water turnover and capacious water storing rumen.

Digesta retention patterns of solute and different-sized particles in camelids compared with ruminants and other foregut fermenters

“…Dromedaries had relatively short MRT solute FS of 11 ± 1 h compared with 19 ± 3 h in Bactrian camels and also shorter MRT solute FS than the smaller species investigated in this study. MRT particle FS were similar in dromedaries when compared with the camelids investigated in this study, which resulted in comparably higher SF values in the FS of dromedaries (also documented by Heller et al 1986c (Silanikove 1994;Hummel et al 2008). Dromedaries, with a comparatively smaller proportionate FS volume than ruminants (Lechner-Doll et al 1990), apparently do not use the FS to the same extent as a water reservoir.…”

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).…”

“…Greater hemicellulose intake with unstructured feeds for diet B and C, in comparison to diet A, was a result of a slightly greater hemicellulose content in the basal diet when pelleted feed replaced ground concentrates and chopped dehydrated lucerne and lower hay intake for those treatments. Retention time in the rumen may be especially important for efficiency of fibre digestion in the addax, a species naturally having a very long digesta retention time in the rumen (Hummel et al, 2008). However, shorter rumen retention time when pelleted feeds were used in the diet does not explain the lower hay intake of diet B and C. More work is needed to determine the effect of different physical structure of the diet, and its ingredient and chemical composition on digesta retention time and digestibility of nutrient in addax.…”

“…In this study we hypothesized that pelleted cereal-based feed would decrease nutrient digestibility and roughage intake by addax (Addax nasomaculatus) -a large Sahara desert grazer with long digesta retention time in the rumen (Hummel et al, 2008). The addax is a critically endangered species of antelope, as classified by the IUCN (IUCN SSC Antelope Specialist Group, 2016).…”