Function of the Lower Intestine and Osmoregulation in the Ostrich: Preliminary Anatomical and Physiological Observations

Skadhauge, Erik; Warui, C. N.; Kamau, John; Maloiy, G. M. O.

doi:10.1113/expphysiol.1984.sp002870

Cited by 41 publications

(20 citation statements)

References 12 publications

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“…The high DM content of Ostrich feces and the low DM content of Emu feces found in the present study correspond to values observed in free-ranging animals (Skadhauge et al 1984, Skadhauge andMaloney 1991). In a similar manner, the length of the colon was reported to correlate with fecal DM content in ruminants (Woodall and Skinner 1993).…”

Section: Discussionsupporting

confidence: 73%

“…The anatomy of Rheas and Emus, with their comparatively short colons, seems to facilitate such a mechanism, whereas its presence seems unlikely in Ostriches due to their long colon (Skadhauge et al 1984) and to date has not been demonstrated using contrast medium studies in Ostriches (Duke et al 1995). If this retrograde transport was achieved by a fluid flow, the solute passage marker could be expected to follow along, with a corresponding pattern of a selective retention.…”

Section: Discussionmentioning

confidence: 99%

“…Despite other general morphological similarities (Livezey and Zusi 2007), Ostriches, Rheas, and Emus differ distinctively in the anatomy of the digestive tract (Figure 1). Ostriches have well-developed, large, sacculated caeca and a particularly long and partly sacculated colon (Skadhauge et al 1984, Hongo et al 2006. In contrast, Rheas evolved particularly large, paired, sacculated caeca without a distinctive colon, and Emus show neither pronounced caeca nor a prominent colon (Cho et al 1984, Herd and.…”

Section: Introductionmentioning

confidence: 99%

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Comparative digesta retention patterns in ratites

Frei

Ortmann

Reutlinger³

et al. 2015

The Auk

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Ratites differ distinctively in the anatomy of their digestive tract. For example, Ostriches (Struthio camelus) have a particularly long, voluminous colon and long paired caeca, Rheas (Rhea spp.) are characterised by a short colon with particularly prominent paired caeca, and Emus (Dromaius novaehollandiae) -have neither very prominent caeca nor a prominent colon. We tested whether digesta excretion patterns corresponded to these differences in anatomy, expecting Ostriches to have the longest and Emus the shortest digesta retention times, and Rheas possibly showing a selective retention of fluids observed in other birds and mammals with prominent caeca. We used 6 Ostriches (97-123kg), 5 Greater Rheas (R. americana, 22-27kg) and 2 Emus (32-34kg) fed a common diet of alfalfa pellets ad libitum in captivity. Intake per unit of metabolic body mass did not differ between Ostriches and Rheas but was significantly higher in Emus, which also displayed higher defecation frequencies and lower fiber digestibility. Mean digesta retention time for small fiber particles (2 mm) differed significantly among species ; Emu: 1.3-1.8h), but there were no differences between the retention of 2 mm or 8 mm particles or a solute marker within species. The shape of the marker excretion curves corresponded to digesta mixing in the digestive tract of Ostriches and Rheas but not Emus. The calculated dry matter gut fill (% of body mass) was significantly higher in Ostriches (1.6-1.8) than Rheas (0.3-1.0) and Emus (0.2). Ostriches had the highest, and Emus the lowest fecal dry matter concentration. These physiological findings match the differences in digestive anatomy and support the concept that in ratites, herbivory -and hence flightlessness -evolved repeatedly in different ways. ABSTRACT Ratites differ distinctively in the anatomy of their digestive tracts. For example, Common Ostriches (Struthio camelus, hereafter Ostriches) have a particularly long, voluminous colon and long, paired caeca; Rheas (Rhea spp.) are characterized by a short colon with particularly prominent paired caeca; and Emus (Dromaius novaehollandiae) have neither prominent caeca nor a prominent colon. We tested whether digesta excretion patterns corresponded to these differences in anatomy, expecting Ostriches to have the longest and Emus the shortest digesta retention times, and Rheas possibly showing a selective retention of fluids observed in other birds and mammals with prominent caeca. We used 6 Ostriches (97-123 kg), 5 Greater Rheas (R. americana, 22-27 kg), and 2 Emus (32-34 kg) fed a common diet of alfalfa pellets ad libitum in captivity. Intake per unit of metabolic body mass did not differ between Ostriches and Greater Rheas but was significantly higher in Emus, which also displayed higher defecation frequencies and lower fiber digestibility. Mean digesta retention time for small fiber particles (2 mm) differed significantly among species (Ostrich: 30-36 h; Greater Rhea: 7-19 h; Emu: 1.3-1.8 h), but there were no differences between the retention o...

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Section: Discussionsupporting

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparative digesta retention patterns in ratites

Frei

Ortmann

Reutlinger³

et al. 2015

The Auk

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“…Skadhauge et al (1984) found that dehydrated ostriches had a U/P ratio of 2.5, whilst in the emu the ratio was 1.4 (Dawson et al, 1985), similar to the value of 1.8 found in the present communication. The low urine osmolalities of the normally hydrated ostriches is similar to that of pigeons , and the increase in osmolalities to over 450 mosm/kg is indicative of the normal concentrating prowess of the nephrons .…”

Section: Osmole Handlingsupporting

confidence: 79%

Effect of water restriction on renal function in ostriches(Struthio camelus)

Levy

Perelman²,

Grevenbroek³

et al. 1990

Avian Pathology

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“…Any suggestion that osmoregulation among the ratites generally follows an evolutionarily conservative, reptile-like pattern, is at variance with data from the ostrich (Withers, 1983). While the water requirements of emus ) are similar to those of the ostrich, the ostrich can produce ureteral urine with a U: P ratio of 2 5 (Withers, 1983) and does not reflux urine into the rectum (Skadhauge, Warui, Kamau & Maloiy, 1984). The adaptation of the two largest of birds to arid habitats has followed quite different courses, however, both obviously successful.…”

Section: Discussionmentioning

confidence: 99%

OSMOTIC AND IONIC REGULATION DURING DEHYDRATION IN A LARGE BIRD, THE EMU (DROMAIUS NOVAEHOLLANDIAE): AN IMPORTANT ROLE FOR THE CLOACA‐RECTUM

1985

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SUMMARYThe emu, a large (40 kg) flightless bird, has low water requirements yet it has a limited ability to produce concentrated urine. To clarify the factors involved in excretion and water conservation by the emu the patterns of excretion during water restriction were examined. Additionally, kidney function was studied, as also was the role of the cloaca and rectum in the final modification of excreta. Following water restriction the osmolality of the excreta fluid increased to a maximum level at 6 d of 428 + 39(8) mosmol (mean + S.E.M. (n)), the urine to plasma ratio being 1v35 + 0-12(8). In normally hydrated birds almost all Na and Cl were excreted in the fluid fraction but a third of the K was associated with the solid fraction of the excreta. After water restriction for 9 d the pattern of excretion of K did not change but the majority of Na (79%) and Cl (73%) were excreted in the solid phase, possibly associated with urates. In ureteral urine most of the nitrogen was excreted as uric acid or urates; a large fraction, 36 +4(4)%, was not identified. The glomerular filtration rate (G.F.R.) was 41-3 + 2.2(6) ml/kg. h. This value is low when compared with other birds and may be related to the large size of the emu. The G.F.R. decreased by 30% after 7 d water restriction. The cloaca-rectum appears to play a major role in the modification of excreta. In vivo perfusion studies showed transepithelial net transport rates of water and major electrolytes to be large. Transport of water from an isosmotic solution, 3-36+0 17 ml/kg.h, was approximately 10 times the maximum value reported for birds previously. The Na and Cl transport rates were also comparatively high.

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Function of the Lower Intestine and Osmoregulation in the Ostrich: Preliminary Anatomical and Physiological Observations

Cited by 41 publications

References 12 publications

Comparative digesta retention patterns in ratites

Comparative digesta retention patterns in ratites

Effect of water restriction on renal function in ostriches(Struthio camelus)

OSMOTIC AND IONIC REGULATION DURING DEHYDRATION IN A LARGE BIRD, THE EMU (DROMAIUS NOVAEHOLLANDIAE): AN IMPORTANT ROLE FOR THE CLOACA‐RECTUM

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