528 research outputs found
Dr. Daryl Cumber Dance – Faculty Author Interview
No full textDr. Daryl Cumber Dance, Professor of English Emerita, discusses her new book, In Search of Annie Drew: Jamaica Kincaid’s Mother and Muse, published recently by the University of Virginia Press. In this provocative new book, Daryl Dance argues that everything Jamaica Kincaid has written, regardless of its apparent theme, actually relates to Kincaid’s efforts to free herself from her mother, whether her subject is ostensibly other family members, her home nation, a precolonial world, or even Kincaid herself
Reticular contraction frequency and ruminal gas dome development in goats do not differ between grass and browse diets
No full textIn investigations of differences between ruminant species feeding on browse or grass, it is often unclear whether observed differences are animal‐ or forage‐specific. Ruminant species have been classified as ‘moose‐type’, with little rumen content stratification, or ‘cattle‐type’ with a distinct rumen contents stratification, including a gas layer. To which extent putative differences in forestomach motility are involved in these patterns is unknown. Using sonography, we investigated the frequency of reticular contractions and the stratification of rumen contents in goats fed exclusively on grass hay (n = 6) or dried browse (n = 5) directly after feeding, and after another 6 and 12 h with no access to feed. The frequency of reticular contractions decreased from immediately after feeding (1.8 ± 0.3 min(−1)) to 6 h afterwards (1.2 ± 0.2 min(−1)) and then remained constant, with no difference between diets. A gas dome became more visible over time, but neither its incidence nor its extent differed between diets. The results are in accord with classifying goats as ‘cattle‐type’ in terms of their digestive physiology, and they add to a growing body of evidence that differences in digestive physiology between ruminant species are more due to species characteristics than different kinds of ingested forages
Data repository – Figure S1 and description of the raw files (*.nms) and related metadata for "Dental microwear texture gradients in guinea pigs reveal that material properties of the diet affect chewing behaviour"
No full textThis digital folder contains the supplementary Figure S1 and the dataset of the publication “Dental microwear texture gradients in guinea pigs reveal that material properties of the diet affect chewing behaviour” by Daniela E. Winkler, Marcus Clauss, Maximilian Rölle, Ellen Schulz-Kornas, Daryl Codron, Thomas M. Kaiser and Thomas Tütken published in Journal of Experimental Biology July 2021 available via DOI: https://doi.org/ 10.1242/jeb.242446
The ecological and evolutionary significance of browsing and grazing in savanna ungulates
No full textIncludes bibliographical references (leaves 175-208)
Comparative omasum anatomy in ruminants: Relationships with natural diet, digestive physiology, and general considerations on allometric investigations
No full textThe Ruminant sorting mechanism protects teeth from abrasives
No full textDental wear due to ingestion of dust and grit has deleterious consequences. Herbivores that could not wash their food hence had to evolve particularly durable teeth, in parallel to the evolution of dental chewing surface complexity to increase chewing efficacy. The rumen sorting mechanism increases chewing efficacy beyond that reached by any other mammal and has been hypothesized to also offer an internal washing mechanism, which would be an outstanding example of an additional advantage by a physiological adaptation, but in vivo evidence is lacking so far. Here, we investigated four cannulated, live cows that received a diet to which sand was added. Silica in swallowed food and feces reflected experimental dietary sand contamination, whereas the regurgitate submitted to rumination remained close to the silica levels of the basal food. This helps explain how ruminants are able to tolerate high levels of dust or grit in their diet, with less high-crowned teeth than nonruminants in the same habitat. Palaeo-reconstructions based on dental morphology and dental wear traces need to take the ruminants’ wear-protection mechanism into account. The inadvertent advantage likely contributed to the ruminants’ current success in terms of species diversity
Herbivory and body size: Allometries of diet quality and gastrointestinal physiology, and implications for herbivore ecology and dinosaur gigantism
Full text linkDigestive physiology has played a prominent role in explanations for terrestrial herbivore body size evolution and size-driven diversification and niche differ- entiation. This is based on the association of increasing body mass (BM) with diets of lower quality, and with putative mechanisms by which a higher BM could translate into a higher digestive efficiency. Such concepts, however, often do not match empirical data. Here, we review concepts and data on terrestrial herbivore BM, diet quality, digestive physiology and metabolism, and in doing so give examples for problems in using allometric analyses and extrapolations. A digestive advantage of larger BM is not corroborated by conceptual or empirical approaches. We suggest that explanatory models should shift from physiological to ecological scenarios based on the association of forage quality and biomass availability, and the association between BM and feeding selectivity. These associations mostly (but not exclusively) allow large herbivores to use low quality forage only, whereas they allow small herbivores the use of any forage they can physically manage. Examples of small herbivores able to subsist on lower quality diets are rare but exist. We speculate that this could be explained by evolutionary adaptations to the ecological opportunity of selective feeding in smaller animals, rather than by a physiologic or metabolic necessity linked to BM. For gigantic herbivores such as sauropod dinosaurs, other factors than digestive physiology appear more promising candidates to explain evolutionary drives towards extreme BM
Dry matter and digesta particle size gradients along the goat digestive tract on grass and browse diets
No full textPhysical properties of the digesta vary along the ruminant digestive tract. They also vary within the forestomach, leading to varying degrees of rumen contents stratification in `moose-type' (browsing) and `cattle-type' (intermediate and grazing) ruminants. We investigated the dry matter concentration (DM) and the mean digesta particle size (MPS) within the forestomach and along the digestive tract in 10 goats fed grass hay or dried browse after a standardized 12-h fast, euthanasia and freezing in the natural position. In all animals, irrespective of diet, DM showed a peak in the omasum and an increase from caecum via colon towards the faeces and a decrease in MPS between the reticulum and the omasum. Both patterns are typical for ruminants in general. In the forestomach, there was little systematic difference between more cranial and more caudal locations (`horizontal stratification'), with the possible exception of large particle segregation in the dorsal rumen blindsac on the grass diet. In contrast, the typical (vertical) contents stratification was evident for DM (with drier contents dorsally) and, to a lower degree, for MPS (with larger particles dorsally). Although evident in both groups, this stratification was more pronounced on the grass diet. The results support the interpretation that differences in rumen contents stratification between ruminants are mainly an effect of species-specific physiology, but can be enhanced due to the diet consumed
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