(2008). The morphophysiological adaptations of browsing and grazing mammals. In: Gordon, I J [et al.]. The ecology of browsing and grazing. Berlin, 47-88. Postprint available at: http://www.zora.uzh.ch Posted at the Zurich Open Repository and Archive, University of Zurich. http://www.zora.uzh.ch Originally published at: Gordon, I J [et al.] 2008. The ecology of browsing and grazing. Berlin, 47-88. The morphophysiological adaptations of browsing and grazing mammals AbstractThere has been a continous debate whether there are fundametal morphophysiological differences in the ingestive apparatus (head, teeth) and the digestive tract between browsing and grazing herbivores. A particular characteristic of this debate appears to be that while there is a wealth of publications on such potential differences, the supposed undelying differences between browse and grass have rarely been analysed quantitatively. In this chapter, we first review the actual state of knowledge on those properties of browse and grass that appear relevant for the ingestive and digestive process, and then deduct hypotheses as to how one would assume that browsers and grazers differ due to these characteristics. We address the methodological issues involved in actually testing these hypotheses, with emphasis on the influence of body mass and phylogenetic descent. Finally, we present a literature compilation of statistical tests of differences between the feeding-types. Although in general, the published tests support many hypothesized differences, there is still both a lack of comparative data, and a lack of analyses with phylogenetic control, on different taxonomic levels. However, the published material appears to indicate that convergent evolutionary adaptations of browsing and grazing herbivores to their diet represent a rewarding area of research. The Morphophysiological Adaptations of Browsing and Grazing MammalsMarcus Clauss, Thomas Kaiser, and Jürgen Hummel IntroductionAnimals represent adaptations to particular ecological niches they occupy or once occupied.Studying the correlation between a given set of characteristics of an ecological niche and the morphological and physiological adaptations of organisms to these characteristics is one of the most basic approaches to comparative biology, and has fuelled scientific interest for generations (Gould 2002). However, current scientific standards cannot be met by mere descriptions of both the characteristics of the niche and the organism, and a (hypothetical) intuitive explanation for the adaptive relevance of the latter; the presence or absence of a characteristic must be demonstrated in sound statistical terms (Hagen 2003) 1 ideally supported by experimental data (from in vivo, in vitro, or model assays) on its adaptive relevance.In this chapter, we adopt an approach that first presents the relevant characteristics of the ecological niche of the 'grazer' (GR) and of the 'browser' (BR), outlines hypotheses based on these characteristics, and finally addresses examples where such hypotheses h...

Summary1. Differences in digestive physiology between browsing and grazing ruminant feeding types have been discussed extensively. The potentially underlying differences in fermentative behaviour of forage plants have received much less attention. 2. In this study, different groups of temperate forage plants (grasses, browse leaves and twigs, herbs and legumes) were compared in their chemical composition and fermentative behaviour. They were evaluated via an in vitro fermentation system (modified Hohenheim gas test), and relevant fermentation parameters such as maximal gas production and relative gas production rate were calculated. 3. Grasses generally had a higher NDF (neutral detergent fibre = total cell wall) content than browse leaves, herbs and legumes, while browse leaf cell wall was more lignified than that of herbs, legumes and grass. 4. With respect to fermentation parameters, grass had the highest maximal gas production, followed by herbs and legumes, and the lowest maximal gas production in browse leaves and twigs. Relative gas production rate was highest in herbs and legumes, while that of grass and browse was lower. As expected, browse twigs had the lowest nutritional value. 5. Dicot material reached given setpoints of absolute gas production rate like 1·0 or 0·5 mL gas/(200 mg dry matter × h) faster than grass material. Based on these results, a longer passage time of food particles seems to be adaptive for grazing ruminants, as over a wide range of fermentation times, absolute gas production rate is higher in grass compared with dicots. Especially for browse leaves, a higher intake level should be expected to balance energy requirements of animals relying on this forage type.

Sauropod dinosaurs, the dominant herbivores throughout the Jurassic, challenge general rules of large vertebrate herbivory. With body weights surpassing those of any other megaherbivore, they relied almost exclusively on pre-angiosperm plants such as gymnosperms, ferns and fern allies as food sources, plant groups that are generally believed to be of very low nutritional quality. However, the nutritive value of these taxa is virtually unknown, despite their importance in the reconstruction of the ecology of Mesozoic herbivores. Using a feed evaluation test for extant herbivores, we show that the energy content of horsetails and of certain conifers and ferns is at a level comparable to extant browse. Based on our experimental results, plants such as Equisetum, Araucaria, Ginkgo and Angiopteris would have formed a major part of sauropod diets, while cycads, tree ferns and podocarp conifers would have been poor sources of energy. Energy-rich but slow-fermenting Araucaria, which was globally distributed in the Jurassic, was probably targeted by giant, high-browsing sauropods with their presumably very long ingesta retention times. Our data make possible a more realistic calculation of the daily food intake of an individual sauropod and improve our understanding of how large herbivorous dinosaurs could have flourished in preangiosperm ecosystems.

The mesowear method evaluates the wear patterns of herbivore cheek teeth by 2 visually evaluating the facet development of the occlusal surfaces. It thus allows 3 classification of most herbivorous ungulates into browsers, grazers or intermediate 4 feeders, due to the fact that in grazers, tooth wear is characterized by a 5 comparatively high degree of abrasion, most probably due to the presence of 6 silicacious phytoliths in grasses, a higher amount of dust and grit adhering to their 7 forage, or both. It has been suggested that excessive tooth wear could be a 8 particularly limiting factor in the husbandry of captive large browsing species, and 9 major tooth wear was demonstrated in captive as compared to free-ranging giraffe. If 10 this increased tooth wear in captivity was an effect of feeding type and diets fed, then 11 it would be expected that other browsing species are affected in a similar manner. In 12 order to test this hypothesis, we investigated the dental mesowear pattern in captive 13 individuals of 19 ruminant species and compared the results to data on free-ranging 14 animals. Compared to free-ranging populations, captive browsers show a 15 significantly more abrasion-dominated tooth wear signal. The reverse applies to 16 captive grazers, which tend to show a less abrasion-dominated wear in captivity. 17Captive ruminants were generally more homogenous in their wear signature than 18 free-ranging ruminants. If grit contamination in the natural habitat is a major cause of 19 dental wear in grazers, then diets in captivity, although similar in botanical 20 composition, most likely contain less abrasives due to feeding hygiene. If dental wear 21 is one of the major factors limiting longevity, then captive grazers should achieve 22 longer lifespans than both captive browsers and free-ranging grazers. In particular 23 with respect to browsers, the results suggest that captive feeding regimes could be 24 improved.

Problem statement: The Oryx antelope is a grazing ruminant of the Bovidae family. The macroscopic anatomy of the stomach in one adult Oryx dammah, an extinct species in the wild, was described. Approach: The stomach of the Oryx was composed of the four classic compartments of the ruminants. The weight of all the full stomach was 21.5 kg. The ruminal papillae were distributed unevenly in the rumen. Results: The maximum height of the cristae reticuli was 0.3 cm. The Cellulae reticuli were divided and contained secondary and tertiary crests. The Curvatura omasi measured 30.0 cm and the omasum had 15 primary, 9 secondary, 30 tertiary and 34 cuaternary Laminae omasi. The abomasum had about 17 Plicae spirales abomasi. Conclusion/Recommendations: We concluded that the stomach morphology of the Oryx had characteristics of the others grazing feeders ruminants. An important limitation of this study is the fact that we used only one animal, further studies of the digestive system of this species are necessary.

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Processing of ingesta particles plays a crucial role in the digestive physiology of herbivores. In the ruminant forestomach different sized particles are stratified into a small and a large particle fraction and only the latter is regurgitated and remasticated to smaller, easier-to-digest particles. In contrast, it has been suggested that in non-ruminating foregut fermenters, such as hippopotamuses, larger particles should be selectively excreted since they tend to be digested at a slower rate and hence can be considered intake-limiting bulk. In our study we determined the mean retention time (MRT) of fluids and different sized particles (2 mm and 10 mm) in six pygmy hippos (Hexaprotodon liberiensis) and six banteng (Bos javanicus) on a diet of fresh grass at two intake levels. We used cobalt ethylendiamintetraacetate (Co-EDTA) as fluid and chromium (Cr)-mordanted fibre (2 mm) and cerium (Ce)-mordanted fibre (10 mm) as particle markers, mixed in the food. Average total tract MRT for fluid, small and large particles at the high intake level was 32, 76 and 73 h in pygmy hippos and 25, 56 and 60 h in banteng, and at the low intake level 39, 109, and 105 h in pygmy hippos and 22, 51 and 58 h in banteng, respectively. In accordance with the prediction, large particles moved faster than, or as fast as the small particles, through the gut of pygmy hippos. In contrast, large particles were excreted slower than the small particles in the ruminant of this study, the banteng. Pygmy hippos had longer retention times than the banteng, which probably compensate for the less efficient particle size reduction. Although the results were not as distinct as expected, most likely due to the fact that ingestive mastication of the larger particle marker could not be prevented, they confirm our hypothesis of a functional difference in selective particle retention between ruminating and non-ruminating foregut fermenters.