We measured parameters of molar progression and dental function in the brush-tailed rock-wallaby (Petrogale pencilliata) (a browser/grazer) and compared them with data from the tammar wallaby (Macropus eugenii) (a grazer) and the parma wallaby (Macropus parma) (a grazer/browser).Although the mean value of the molar index (MI) was higher in rock-wallabies than in parma and tammar wallabies the mean rate of increase of log(MI) with log(body mass) was similar in the three species. Reported differences between these species in their rates of molar progression with age may therefore result from differences in their rates of bodily growth. The findings indicate that molar progression in the rock-wallaby is governed by the growth of the bones of the viscerocranium (mesial shift), rather than by diet-induced movement of the teeth within the bones of the viscerocranium (mesial drift), and was not influenced by the persistence of P4 premolars. It is therefore unlikely that differences in the rate of molar progression are directly linked to differences in diet.The relationship between functional dental parameters and body mass differed between brush-tailed rock-wallabies and tammar wallabies, species of differing dietary habit, but did not differ between brush-tailed rock-wallabies and parma wallabies, species of more similar dietary habit. Thus the total length of upper transverse lophine ridges and the interlophine distances of the M1 to M3 upper molars of brush-tailed rock-wallabies were not different from those of parma wallabies but were significantly greater than those of tammar wallabies. These differences can be interpreted in terms of greater emphasis on crushing/grinding of browse in the rock-wallabies and parma wallabies.
We examined gizzard morphology and diet particle size reduction in broiler chickens fed a wheat-based diet that was offered in either a mash or a pelleted form. The pelleted diet had a lower proportion of coarse particles on wet sieving. Birds fed the mash diet had a significantly larger gizzard mass per unit body mass. The gizzards of all birds increased uniformly in size, there being no significant change either in the ratio of content to empty mass or in the ratio of gizzard length to breadth with diet. Thus, there was no tendency for coarse particles to accumulate in the gizzards of bird fed the mash diet. The relative proportion of all classes of particles below 0.500mm was increased and the relative proportion of all particle classes above 0.500mm was reduced in birds regardless of feed form. The relative increase of particles in all classes below 0.500mm was greater in birds fed mash feed. However, digesta exiting the gizzard of birds fed mash diet contained significantly greater amounts of particles of size classes 1mm and greater than digesta of those fed the pelleted diet. Thus, whilst the gizzard operates to generally reduce particle sizes above 0.500mm and increase those below this size, this reduction is not uniform and likely to be a probabilistic function as it is in the human mouth.
Ostriches are the largest living birds and are endemic to hot arid and semi-arid climates.Their kidneys are relatively large and can produce concentrated urine, but no detailed renal studies have been conducted.In mammals, a high protein diet increases both glomerular filtration rate (GFR) and urine flow rate (UFR).Three adult female ostriches (mean body mass 108 kg) were fed four pelleted diets containing 1.2 to 2.4 % N (7.5-15 % CP).Each trial consisted of 10-day adaptation, followed by a 6-day period during which all excreta was collected.Creatinine concentration of the plasma ([Cr] pl ), urine ([Cr] u ) and excreta were measured.GFR was calculated as the total daily excreted creatinine divided by [Cr] pl .UFR was calculated as the total daily excreta creatinine output divided by the [Cr] u .Increasing dietary CP increased the GFR, but had no affect on UFR (Fig. 1).In contrast Goldstein et al. (2001) found that increased protein intake in sparrows increased UFR, but not GFR.GFR and UFR of ostriches in this study averaged 47.2 ± 5.5 and 2.46 ± 0.26 mL/min, respectively.This GFR value is lower than that predicted allometrically for a 100 kg bird, but similar to that predicted for avian species from arid habitats (Bennett and Hughes 2003).
Spontaneous and oxytocin induced contractile activity was quantified in the bicornuate uteri of pregnant rabbits maintained in situ, using data from two- and uni- dimensional video spatiotemporal maps (VSTM) of linear and area strain rate and compared statistically. Spontaneous contractions occurred over a range of frequencies between 0.1 and 10 cpm, in gravid animals at 18-21 and at 28 days of gestation, and propagated both radially and longitudinally over the uterine wall overlying each foetus. Patches of contractions were randomly distributed over the entire surface of the cornua and were pleomorphic in shape. No spatial coordination was evident between longitudinal and circular muscle layers nor temporal coordination that could indicate the activity of a localised pacemaker. The density and duration of contractions decreased, and their frequency increased with the length of gestation in the non-labouring uterus. Increasing intravenous doses of with oxytocin had no effect on the mean frequencies, or the mean durations of contractions in rabbits of 18-21 days gestation, but caused frequencies to decrease and durations to increase in rabbits of 28 days gestation, from greater spatial and temporal clustering of individual contractions. This was accompanied by an increase in the distance of propagation, the mean size of the patches of contraction, the area of the largest patch of contraction and the overall density of patches. Together these results suggest that progressive smooth muscle hypertrophy and displacement with increasing gestation is accompanied by a decrease in smooth muscle connectivity causing an increase in wall compliance and that oxytocin restores connectivity and decreases compliance, promoting volumetric expulsion rather than direct propulsion of the foetus by peristalsis. The latter effects were reversed by the β2 adrenergic receptor agonist salbutamol thus reducing area of contraction, duration and distance of propagation
Abstract The caeca of the brown kiwi Apteryx mantelli increased in length isometrically with body mass, but wall mass and thus mucosal thickness increased allometrically. Kiwi caeca are sacculate, with greater thickness of mucosa in the proximal portions. The caecal mucosa is similar to the small intestinal mucosa, with well‐developed mucosal folds, villi, and crypts of Lieberkühn or intestinal glands. The solid matter in caecal digesta contained disproportionately large quantities of material that was not retained by a 75 μ m sieve. The per cent of incombustible material (total ash) within the caeca digesta did not differ significantly from those within adjacent small intestinal or rectal segments. The fine particles within the caeca were not composed of fine crystalline uric acid; chemical analyses showed only low levels of uric acid in caecal digesta. These findings indicate that the caeca of this flightless insectivorous ratite are a site for the sequestration and fermentative digestion of fine particulate material, such as plant fibre, fragmented chitin or uric acid crystals.
We explore how foods can be designed to modulate digestion and to promote health by changing the physical properties of digesta. The physical characteristics of digesta are discussed along with their impact on the physiology of digestion with special reference to sites where these characteristics are likely to influence digestive efficiency. Evidence is reviewed regarding the effects of supplementation with viscoactive agents on the flow and mixing of digesta in particular segments of the human gut that, by changing the rheology and liquid permeability of digesta in that segment, influence specific aspects of digestion and absorption.
Tooth morphology of two browsing macropods (brush-tailed rock-wallabies and swamp wallabies), one grazing species (tammar wallaby) and one mixed feeder (parma wallaby) are compared. The dental action of a single tammar wallaby was studied by cinefluoroscopy. Cinefluoroscopy showed independent rotation of each hemi-jaw on occlusion in the tammar, and the disposition of molar striae suggest a similar pattern of jaw movement in all four species. There was a close relationship between incisor and molar action in both grazing and browsing species. Initial occlusion of the anterior facets of the incisors brought about a grasping action in browsing species and a fine cutting action in grazing species. In both grazing and browsing species these incisor actions were coincident with a cutting action by the transverse lophs during molar occlusion. Subsequent independent rotation of each hemi-jaw results in fine cutting by the lateral facets of the incisors, in both grazers and browsers, at the same time as the molar arrays perform a crushing action in browsers and a secondary cutting action in grazing species. Thus the teeth of the four species showed a number of similarities (independent rotation of each hemi-jaw) along with some differences (incisor and molar actions) that appear to represent adaptations for efficient aquisition and oral processing of browse or graze.
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