3,698 research outputs found
Physiological adaptations of ruminants and their potential relevance for production systems
Full text linkABSTRACT Herbivores face the dilemma that the level of feed intake is negatively related to factors that determine digestive efficiency, such as thoroughness of ingesta comminution by chewing, and retention of digesta in the digestive tract. Ruminants have evolved particular adaptations to solve this dilemma. Most ruminants share the characteristic of “digesta washing”: fluid moves through their digestive tract faster than particles, thus effectively washing very fine particles, such as bacteria, out of the digesta plug. As the forestomach is followed by auto-enzymatic digestion, this allows a continuous, increased harvest of microbes from the forestomach. True rumination only evolved twice, in the camelids and the true ruminants. These both evolved a density-dependent sorting mechanism based on physical separation of the digesta by the process of flotation and sedimentation, ensuring that the process of rumination is applied to large particles. Differences in this sorting mechanism might facilitate a faster digesta processing in true ruminants as compared with camelids. The hallmark of ruminant digestive anatomy is the omasum, in which the fluid required for both digesta washing and the reticular separation mechanism is re-absorbed. In ruminants of the tribe Bovini, the omasum has reached the largest size and this group has a particularly great forestomach fluid throughput. Increasing the degree of digesta washing even more should increase microbial harvest from the forestomach and reduce the susceptibility to acidosis. At the same time, it should result in a metabolic state of the microbiome more tuned towards biomass production and less towards methanogenesis. Enhancing the forestomach fluid throughput by selective breeding could represent a promising way to further advance the productivity of the ruminant digestive tract
Teeth and the gastrointestinal tract in mammals: when 1 + 1 = 3
No full textBoth teeth and the digestive tract show adaptations that are commonly interpreted in the context of trophic guilds—faunivory, herbivory and omnivory. Teeth prepare food for the digestive tract, and dental evolution focuses on increasing durability and functionality; in particular, size reduction of plant particles is an important preparation for microbial fermentative digestion. In narratives of digestive adaptations, microbes are typically considered as service providers, facilitating digestion. That the majority of ‘herbivorous’ (and possibly ‘omnivorous’) mammals display adaptations to maximize microbes' use as prey—by harvesting the microbes multiplying in their guts—is less emphasized and not reflected in trophic labels. Harvesting of microbes occurs either via coprophagy after separation from indigestible material by a separation mechanism in the hindgut, or from a forestomach by a ‘washing mechanism’ that selectively removes fines, including microbes, to the lower digestive tract. The evolution of this washing mechanism as part of the microbe farming niche opened the opportunity for the evolution of another mechanism that links teeth and guts in an innovative way—the sorting and cleaning of not-yet-sufficiently-size-reduced food that is then re-submitted to repeated mastication (rumination), leading to unprecedented chewing and digestive efficiency. This article is part of the theme issue ‘Food processing and nutritional assimilation in animals’.Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung 50110000171
Is there a difference in ruminal fermentation control between cattle and sheep? A meta-analytical test of a hypothesis on differential particle and fluid retention
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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
sj-pdf-1-lan-10.1177_00236772211036572 - Supplemental material for Use of running plates by floor housed rats: A pilot study
No full textSupplemental material, sj-pdf-1-lan-10.1177_00236772211036572 for Use of running plates by floor housed rats: A pilot study by Jessica Frei, Marcus Clauss, Daniela E Winkler, Thomas Tütken and Louise F Martin in Laboratory Animals</p
Marcus Joseph Wright memoirs, MSS.1585
No full textAbstract: An incomplete typescript copy (18 pp.) of, "Memoirs of Brigadier General Marcus J. Wright, CSA."Scope and Content Note: The collection contains an incomplete typescript copy (18 pp.) of, "Memoirs of Brigadier General Marcus J. Wright, CSA," which includes a family genealogy, and accounts of his early life in Tennessee and his career.Biographical/Historical Note: Confederate General and author from Tennessee
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