Caecal decomposition of uric acid in captive and free ranging willow ptarmigan (Lagopus lagopus lagopus)

Mortensen, Atle; Tindall, A. R.

doi:10.1111/j.1748-1716.1981.tb06715.x

Cited by 46 publications

(13 citation statements)

References 18 publications

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“…Indeed, if the immediate source of the microbial N was the host's urea, uric acid, or high-protein urate ''spheres'' (Braun, 2003), then one might ask whether the net effect of this kind of microbial cycling of N is anything more than a futile cycle, at least from the perspective of the host's N economy. Similarly, even if the microbes synthesize nonessential amino acids which the host absorbs (Mortensen & Tindall, 1981), the benefits are not obvious. The uric acid or urea originally derives from waste ammonia in the host's bloodstream -ammonia that can be converted to nonessential amino acids without any microbial assistance.…”

Section: The Role Of the Avian Hindgut In Nutritionmentioning

confidence: 99%

The integration of digestion and osmoregulation in the avian gut

2009

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We review digestion and osmoregulation in the avian gut, with an emphasis on the ways these different functions might interact to support or constrain each other and the ways they support the functioning of the whole animal in its natural environment. Differences between birds and other vertebrates are highlighted because these differences may make birds excellent models for study and may suggest interesting directions for future research. At a given body size birds, compared with mammals, tend to eat more food but have less small intestine and retain food in their gastrointestinal tract (GIT) for shorter periods of time, despite generally higher mass-specific energy demands. On most foods, however, they are not less efficient at digestion, which begs the question how they compensate. Intestinal tissue-specific rates of enzymatic breakdown of substrates and rates of active transport do not appear higher in birds than in mammals, nor is there a demonstrated difference in the extent to which those rates can be modulated during acclimation to different feeding regimes (e.g. diet, relative intake level). One compensation appears to be more extensive reliance on passive nutrient absorption by the paracellular pathway, because the avian species studied so far exceed the mammalian species by a factor of at least two- to threefold in this regard. Undigested residues reach the hindgut, but there is little evidence that most wild birds recover microbial metabolites of nutritional significance (essential amino acids and vitamins) by re-ingestion of faeces, in contrast to many hindgut fermenting mammals and possibly poultry. In birds, there is some evidence for hindgut capacity to breakdown either microbial protein or protein that escapes the small intestine intact, freeing up essential amino acids, and there is considerable evidence for an amino acid absorptive capacity in the hindgut of both avian and mammalian hindgut fermenters. Birds, unlike mammals, do not excrete hyperosmotic urine (i.e. more than five times plasma osmotic concentration). Urine is mixed with digesta rather than directly eliminated, and so the avian gut plays a relatively more important role in water and salt regulation than in mammals. Responses to dehydration and high- and low-salt loads are reviewed. Intestinal absorption of ingested water is modulated to help achieve water balance in one species studied (a nectar-feeding sunbird), the first demonstration of this in any terrestrial vertebrate. In many wild avian species the size and digestive capacity of the GIT is increased or decreased by as much as 50% in response to nutritional challenges such as hyperphagia, food restriction or fasting. The coincident impacts of these changes on osmoregulatory or immune function of the gut are poorly understood.

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Section: The Role Of the Avian Hindgut In Nutritionmentioning

confidence: 99%

The integration of digestion and osmoregulation in the avian gut

2009

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“…Avian caeca have diverse functional capabilities that may vary in importance with the diet and nutritional strategy of the species (Clench & Mathias, 1995). Thus, the organ may have a predominantly fermentative function in herbivores such as the capercaille Tetrao urogallus and willow grouse Lagopus lagopus that are known to harbour caecal cellulolytic organisms (Suomalainen & Arhimo, 1945), a water-conserving function in the rock ptarmigan Lagopus mutus (Gasaway, White & Holleman, 1976), a nitrogen-recycling capability in chickens (Moretensen & Tindell, 1981), a role in defence against pathogens (Glick, Chang & Jaap, 1956;Barnes, 1977) and a site for the synthesis of vitamins by microbial symbionts (Couch et al, 1950). Attempts to correlate the mucosal histology (Naik, 1962) and the gross morphology (Clench & Mathias, 1995 of the caecum with these functions (Duke, 1989;Angel, 1996;DeGolier, Mahoney & Duke, 1999;Jozefiak, Rutkowski & Martin, 2004) have met with limited success.…”

Section: Introductionmentioning

confidence: 99%

Gastrointestinal tract of the brown kiwi (Apteryx mantelli)

et al. 2006

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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 welldeveloped mucosal folds, villi, and crypts of Lieberk¨uhn or intestinal glands. The solid matter in caecal digesta contained disproportionately large quantities of material that was not retained by a 75 mm 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.

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“…Nitrogen conservation has been documented in a variety of Galliformes, such as willow ptarmigan, Gambel's quail, and domestic chickens (Mortensen and Tindall 1981;Campbell and Braun 1986;Son and Karasawa 2000). These birds have large cecae populated by anaerobic microorganisms (Mead 1997;Clench 1999), some of which use uric acid as a major source of carbon and energy (Mead 1997).…”

Section: Discussionmentioning

confidence: 99%

Are the Low Protein Requirements of Nectarivorous Birds the Consequence of Their Sugary and Watery Diet? A Test with an Omnivore

Tsahar

Rio

Arad³

et al. 2005

Physiological and Biochemical Zoology

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Nectar-feeding birds have remarkably low nitrogen requirements. These may be due either to adaptation to a low-protein diet or simply to feeding on a fluid diet that minimizes metabolic fecal nitrogen losses. We measured minimal nitrogen requirements (MNR) and total endogenous nitrogen loss (TENL) in the omnivorous European starling Sturnus vulgaris, fed on an artificial nectar-like fluid diet of varying concentrations of sugar and protein. The MNR and TENL of the birds were similar and even slightly higher than allometrically expected values for birds of the starlings' mass (140% and 103%, respectively). This suggests that the low measured nitrogen requirements of nectar-feeding birds are not simply the result of their sugary and watery diets but a physiological adaptation to the low nitrogen input. We also measured the effect of water and protein intake on the nitrogenous waste form in the excreta and ureteral urine in European starlings. Neither high water intake nor low protein intake increased the fraction of nitrogen excreted as ammonia. Ammonia was excreted at consistently low levels by the starlings, and its concentration was significantly higher in ureteral urine than in excreta. We hypothesize that ureteral ammonia was reabsorbed in the lower intestine, indicating a postrenal modification of the urine.

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Caecal decomposition of uric acid in captive and free ranging willow ptarmigan (Lagopus lagopus lagopus)

Cited by 46 publications

References 18 publications

The integration of digestion and osmoregulation in the avian gut

The integration of digestion and osmoregulation in the avian gut

Gastrointestinal tract of the brown kiwi (Apteryx mantelli)

Are the Low Protein Requirements of Nectarivorous Birds the Consequence of Their Sugary and Watery Diet? A Test with an Omnivore

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