Solute and particle retention in the digestive tract of the Phillip's dikdik (Madoqua saltiana phillipsi), a very small browsing ruminant

Morphological characteristics of the forestomach and reports of the natural diet suggest that dikdiks should have a ‘moose-type’ forestomach physiology with a low degree of selective particle retention. This assumption was tested in feeding experiments with 12 adult Phillip’s dikdiks (Madoqua saltiana phillipsi) on 3 different intake levels, using cobalt-EDTA as a solute marker and a conventional chromium-mordanted fibre (< 2mm; mean particle size 0.63mm) as particle marker. Body mass had no influence on retention time (RT) whereas food intake level clearly had. Drinking water intake was not related to solute marker RT. The particle marker was retained distinctively longer than the solute marker. Comparisons with results in larger ruminants and with faecal particle sizes measured in dikdiks suggested that the particle marker was above the critical size threshold, above which particle delay in the forestomach is not only due to selective particle retention, but additionally due to the ruminal particle sorting mechanism. A second study with a marker of a lower mean particle size (0.17mm) resulted in particle and fluid RT similar to those in other ‘moose-type’ ruminants. Even this smaller particle marker yielded RT that were longer than those predicted by allometric equations based on quarter-power scaling, providing further support for observations that small ruminants generally achieve longer RT and higher digestive efficiencies than expected based on their body size. Die Morphologie des Vormagens und die natürliche Nahrung von Dikdiks lassen vermuten, dass diese eine ‚elchartige’ Verdauungsphysiologie mit geringer selektiver Partikelretention haben. Diese Hypothese wurde in Fütterungsversuchen mit 3 unterschiedlichen Futteraufnahme-Niveaus an 12 adulten Phillip’s Dikdiks (Madoqua saltiana phillipsi) getestet, wobei Kobalt-EDTA als Flüssigkeits- und eine konventionelle chromgebeizte Faser als Partikelmarker (<2mm; mittlere Partikelgröße 0.63mm) verwendet wurden. Die Körpermasse hatte keinen Einfluss auf die Retentionszeit (RT), die Futteraufnahme hingegen schon. Wasseraufnahme hatte keinen Einfluss auf die RT des Flüssigkeitsmarkers. Der Partikelmarker wurde deutlich länger zurückgehalten als der Flüssigkeitsmarker. Vergleiche mit Ergebnissen größerer Wiederkäuer sowie zu Kotpartikelgrößen bei Dikdiks lassen vermuten, dass der Partikelmarker über dem kritischen Grenzwert lag, bei dem Verzögerung im Vormagen nicht nur aufgrund von selektiver Partikelretention, sondern auch aufgrund von Sortiermechanismen stattfindet. Eine 2. Studie mit einem feineren Marker (0.17mm) ergab Partikel- und Flüssigkeits-RT wie bei ‚elchartigen’ Wiederkäuern. Die Partikel-RT war länger als durch allometrische Gleichungen vorhergesagt, was die Vermutung unterstützt, dass kleine Wiederkäuer generell längere RT erreichen und höhere Verdauungseffizienz aufweisen als aufgrund ihrer Körpergrösse erwartet wird.

Blood values of clinically healthy captive beira antelopes (Dorcatragus megalotis) and during an outbreak of fibrinous pleuropneumonia syndrome (FPPS)

Currently the only captive population of beira antelope (Dorcatragus megalotis) is held at the Al Wabra Wildlife Preservation, Qatar. An outbreak of a severe respiratory disease—fibrinous pleuropneumonia syndrome, most likely caused by Mycoplasma ovipneumoniae—led to a marked population decline. Reactive systemic inflammatory (AA) amyloidosis was noted as a chronic manifestation of the disease. Blood samples had been collected for biochemistry and hematology baseline values prior to the outbreak. Population-level changes were analyzed before and during the course of the outbreak in selected blood parameters (white blood cells [WBC], blood urea nitrogen [BUN], and creatinine). The annual population WBC increased and decreased concurrently with the population size, with a significant correlation between the two measures (R = 0.92; P < 0.001). Both BUN and creatinine values were higher during the outbreak. These values peaked at the same time as mortality, which was 1 yr after the WBC peak. These changes were interpreted as the transition from an acute disease with a primary respiratory manifestation into a chronic condition where renal amyloidosis led to chronic renal failure and death. Also, elevated liver values in diseased animals were attributed to amyloidosis. Parallels to a literature report on a lung disease complex caused by M. ovipneumoniae in bighorn sheep (Ovis canadensis) were found. Trends in population-level blood values of the beira antelopes implicate amyloidosis as a significant, longterm consequence of the putative Mycoplasma infection

Retention of solutes and different-sized particles in the digestive tract of the ostrich (Struthio camelus massaicus), and a comparison with mammals and reptiles

Ostriches (Struthio camelus) achieve digesta retention times, digesta particle size reduction and digestibilities equal to similar-sized herbivorousmammals, in contrast to some other avian herbivores. The sequence of digestive processes in their gastrointestinal tract, however, is still unexplored. Using two groups of four ostriches (mean body mass 75.1±17.3 kg) kept on fresh alfalfa, we tested the effect of two intake levels (17 and 42 g dry matter kg−0.75 d−1) on the mean retention time (MRT) of a solute and three different-sized (2, 10, 20 mm) particle markers, mean faecal particle size (MPS), and digestibility. Intake level did not affect MRT, but MPS (0.74 vs. 1.52 mm) and dry matter digestibility (81 vs. 78%). The solute marker (MRT 22–26 h) was excreted faster than the particlemarkers; there was no difference in the MRT of 10 and 20 mmparticles (MRT 28–32 h), but 2 mmparticles were retained longer (MRT 39–40 h). Because the solutemarker was not selectively retained, and wet‐sieving of gut contents of slaughtered animals did not indicate smaller particles in the caeca, the long MRT of small particles is interpreted as intermittent excretion from the gizzard, potentially due to entrapment in small grit. Themarker excretion pattern also showed intermittent peaks for allmarkers in five of the animals,which indicates non-continuous outflow from the gizzard.When adding our data to literature data on avian herbivores, a dichotomy is evident, with ostrich and hoatzin (Opisthocomus hoazin) displaying longMRTs, high digestibilities, and gut capacities similar tomammalian herbivores, and other avian herbivores such as grouse, geese or emuswith shorter MRTs, lower fibre digestibilities and lower gut capacities. In the available data for all avian herbivores where food intake and MRTs were measured, this dichotomy and food intake level, but not body mass, was related to MRT, adding to the evidence that body mass itself may not be sole major determinant of digestive physiology. The most striking difference between mammalian and avian herbivores from the literature is the fundamentally lower methane production measured in the very few studies in birds including ostriches, which appears to be at the level of reptiles, in spite of general food intake levels of amagnitude as inmammals. Further studies in ostriches and other avian herbivores are required to understand the differences in digestivemechanisms between avian and mammalian herbivores

Digesta kinetics in gazelles in comparison to other ruminants: Evidence for taxon-specific rumen fluid throughput to adjust digesta washing to the natural diet

Digesta flow plays an important role in ruminant digestive physiology. We measured the mean retention time (MRT) of a solute and a particle marker in the gastrointestinal tract (GIT) and the reticulorumen (RR) of five gazelles and one dikdik species. Species-specific differenceswere independent frombodymass (BM)or food intake. Comparative evaluations (including up to 31 other ruminant species) indicate that MRT GIT relate positively to BM, and are less related to feeding type (the percentage of grass in the natural diet, %grass) than MRT RR. The MRTparticleRR is related to BM and (as a trend) %grass, matching a higher RR capacity with increasing BM in grazers compared to browsers. MRTsoluteRR is neither linked to BM nor to %grass but shows a consistent phylogenetic signal. Selectivity factors (SF; MRTparticle/MRTsolute, proxies for the degree of digesta washing) are positively related to %grass, with a threshold effect, where species with N20% grass have higher SF. These findings suggest that in different ruminant taxa, morphophysiological adaptations controlling MRTsoluteRR evolved to achieve a similar SF RR in relation to a %grass threshold. A high SF could facilitate an increased microbial yield from the forestomach. Reasons for variation in SF above the %grass threshold might represent important drivers of ruminant diversification and await closer investigation

Solute and particle retention in the digestive tract of the Phillip's dikdik (Madoqua saltiana phillipsi), a very small browsing ruminant: Biological and methodological implications

Morphological characteristics of the forestomach, as well as reports of a natural diet that mostly excludes monocots, suggest that dikdiks (Madoqua spp.), among smallest extant ruminants, should have a ‘moosetype’ forestomach physiology characterised by a low degree of selective particle retention. We tested this assumption in a series of feeding experiments with 12 adult Phillip's dikdiks (Madoqua saltiana phillipsi) on three different intake levels per animal, using cobalt-EDTA as a solute marker and a ‘conventional’ chromiummordanted fibre (b2 mm; mean particle size 0.63 mm) marker for the particle phase. Body mass had no influence on retention measurements, whereas food intake level clearly had. Drinking water intake was not related to the retention of the solute marker. In contrast to our expectations, the particle marker was retained distinctively longer than the solute marker. Comparisons with results in larger ruminants and with faecal particle sizes measured in dikdiks suggested that in these small animals, the chosen particle marker was above the critical size threshold, above which particle delay in the forestomach is not only due to selective particle retention (as compared to fluids), but additionally due to the ruminal particle sorting mechanism that retains particles above this threshold longer than particles below this threshold. A second study with a similar marker of a lower mean particle size (0.17 mm, which is below the faecal particle size reported for dikdiks) resulted in particle and fluid retention patterns similar to those documented in other ‘moose-type’ ruminants. Nevertheless, even this smaller particle marker yielded retention times that were longer than those predicted by allometric equations based on quarter-power scaling, providing further support for observations that small ruminants generally achieve longer retention times and higher digestive efficiencies than expected based on their body size

Energy requirements and metabolism of the Phillip's dikdik (Madoqua saltiana phillipsi)

Basal metabolic rates in mammals are mainly determined by body mass, but also by ecological factors. Some mammalian species inhabiting hot, dry environments were found to have lower metabolic rates compared to temperate species. We studied energy metabolism in Phillip’s dikdik (Madoqua saltiana phillipsi), a small antelope inhabiting xeric shrubland habitats in the Eastern 'horn' of Africa, and compared results to literature data. We measured body mass (BM) changes and digestibility in 12 adults kept on different food intake levels to determine, by extrapolation to zero BM change, maintenance energy requirements (MEm) for metabolizable energy (ME). The MEm averaged at 404 ± 20 kJ ME kg BM -0.75 d-1. In addition we conducted 24 h-chamber respirometry with seven fed (non-fasted) individuals. Their mean metabolic rate as calculated from oxygen consumption was 403 ± 51 kJ kg BM-0.75 d-1, corroborating the results of the feeding trials. Selecting the 20 lowest values of the respiration measurement period to estimate resting metabolic rate (RMR) resulted in a mean RMR of 244 ± 39 kJ kg BM-0.75 d-1, which was numerically (but not significantly) lower than the expected basal metabolic rate of 293 kJ kg BM-0.75 d-1. Therefore, resting metabolism was similar to the expected average basal metabolism of a mammal of this size, which suggests a comparatively low metabolic rate in dikdiks. Compared to literature data Phillip’s dikdiks have a MEm similar to measurements reported for small domestic ruminants, but considerably lower than those reported for other wild ruminant species inhabiting temperate and cold climates