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In 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., (© 2021 The Authors. Journal of Animal Physiology and Animal Nutrition published by Wiley-VCH GmbH.)

Sieve analyses of hindgut contents of horses as well as observations in horses where plastic markers had been applied to a caecal cannula suggested that there may be a discrimination by particle size in the passage or retention of digesta. Here, we performed a similar experiment with five caecum-cannulated horses (562 ± 31 kg) fed a constant amount (6.81 kg dry matter/day) of grass hay. Passage markers representing the liquid (Co-EDTA) as well as the particulate digesta phase (Yb-undefined; Cr mordanted fibre 1-2 mm; Ce-mordanted fibre 8 mm) were given as a pulse-dose into the cannula to measure their mean retention times (MRT). The MRTs were compared by repeated-measurements analysis of variance. The MRT in the hindgut was 22.2 ± 2.4 h for Co, 25.0 ± 3.4 h for Yb, 26.2 ± 1.6 h for Cr and 26.3 ± 1.5 h for Ce. Whereas differences between the particle marker MRTs were not significant (p adj.  > 0.05), significant differences were observed between the solute marker Co and each of the particle markers Cr and Ce (p adj.  < 0.009). The results confirm the well-known significant, albeit small, difference in MRT in horses between the fluid and the particle digesta phase, and corroborate another recent study that used a combination of whole, marked hay and individual marker analysis in different particle size fractions of the faeces, which also did not detect a selective retention of any particle size class., (© 2022 The Authors. Journal of Animal Physiology and Animal Nutrition published by Wiley-VCH GmbH.)

Changes in digesta dry matter (DM) and mean digesta particle size (MPS) along the gastrointestinal tract are well known in ruminants, but not in camelids. We collected digesta from the dorsal (d) and ventral (v) first forestomach compartment (C1), the second forestomach compartment (C2), three proximal segments and the subsequent glandular part of the third compartment (C3A-D), the caecum and the faeces twelve llamas (Lama glama). DM analysis indicates the presence of digesta stratification in the C1, the presence of fluid in the C2 to facilitate the sorting function of this compartment, the fluid-absorbing function of the proximal parts of the C3, the secretion of enzymes and digestive acids in the C3D, and the water-resorbing function of the lower intestinal tract. These findings illustrate the functional resemblance between the gastrointestinal tract of camelids and cattle-like ruminants (C1 equivalent to the rumen with stratified contents, C2 to the reticulum, C3A/B/C to the omasum and C3D to the abomasum). MPS analysis revealed a progressive reduction in MPS from the C1 to the distal C3. This gradual transition is different from the clear-cut threshold in ruminants between the reticulum and the omasum and had so far only been described in dromedaries (Camelus dromedarius). These findings indicate that regardless of the convergent property of rumination and resemblance of general mechanisms involved in contents stratification and particle sorting, differences between ruminants and camelids exist that could be interpreted as a more efficient functionality of the ruminant forestomach., (© 2019 Blackwell Verlag GmbH.)

Irrigation agriculture of hot climates suffers from rapid soil organic carbon (C) turnover, high nitrogen (N) leaching and gaseous losses. In this context, we explored the possibility of supplementing ruminants with activated charcoal (AC) and condensed tannins (CT) to increase faecal concentration of long-lived C and slowly decomposable N. For this purpose, we fed AC and quebracho tannin extract (QTE, source of CT) to goats and determined nutrient digestibility, digesta passage and composition of faeces. The feeding trial comprised three periods, with 24 male goats assigned to five treatments and a control. On dry matter (DM) basis, the basal diet (control) consisted of 50% hay, 46.5% crushed maize and 3.5% soya bean meal. Treatment diets contained (on DM basis) 2% and 4% QTE (QTE2, QTE4), 1.5% and 3.0% AC (AC1.5, AC3.0) and a mixture of 2% QTE plus 1.5% AC (QTEAC). Samples of feed, refusals and faeces were analysed for chemical constituents; digesta passage was computed with a one-compartment Gamma-2 model from pulse-dose application of ytterbium-mordanted fibre and quantitative collection of faeces during 7 days. Compared to the control, organic matter and N digestibility were reduced with QTE2 and QTE4 (p ≤ 0.001), that of neutral and acid detergent fibre (NDFom, ADFom) decreased with QTE4, QTEAC and both AC treatments (p ≤ 0.001). Ruminal particle passage ranged from 0.051 h -1 (QTEAC) to 0.056 h -1 (control; p > 0.05). Apart from the correlation between total tract mean retention time and faecal C/N ratio (r = -0.35), passage parameters did not affect faeces quality. While faecal N concentration was not altered by both additives, AC enhanced faecal NDFom, ADFom and C concentrations (p ≤ 0.001). Whereas feeding up to 3% AC might slow down the decomposition of manure in the field without negatively affecting the digestive physiology of goats, including QTE seems not advantageous from a physiological and nutrient recycling perspective., (Journal of Animal Physiology and Animal Nutrition © 2016 Blackwell Verlag GmbH.)

Physical 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., (Journal of Animal Physiology and Animal Nutrition © 2016 Blackwell Verlag GmbH.)