Physiological roles and regulation of transport activities in the avian lower intestine

Laverty, Gary; Skadhauge, Erik

doi:10.1002/(sici)1097-010x(19990301/01)283:4/5<480::aid-jez19>3.0.co;2-g

Cited by 18 publications

(16 citation statements)

References 84 publications

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“…As discussed in the previous section, nutrients that escape the small intestine might yet be recovered in the hindgut (Alpers, 1994; Laverty & Skadhauge, 1999). If the hindgut mainly plays this scavenger role, then we must ask what is its added value above and beyond an equivalent mass of small intestine?…”

Section: The Role Of the Avian Hindgut In Nutritionmentioning

confidence: 99%

“…The transport of salt and water across the avian hindgut appears to be hormonally regulated; both mineralocorticoids and glucocorticoids have been implicated (Laverty & Skadhauge, 1999). In particular, electrogenic Na + channel activity appears to be modulated by plasma levels of aldosterone.…”

Section: The Role Of the Avian Gut In Salt And Water Regulationmentioning

confidence: 99%

“…Biological Reviews 84 (2009) other studies that indicate the presence of free essential amino acids in the lumen of the hindgut. Caecectomized poultry excrete more amino acids in faeces than do controls (Green et al, 1987a, b;Johns et al, 1986;Kessler, Nguyen & Thomas, 1981;Parsons, 1986), suggesting that dietary amino acids which escape proximal absorption flow into the caeca and that the caeca play some role in absorbing these nutrients (Laverty & Skadhauge, 1999). Based on tests of true digestibility or net protein utilization (which takes into account both digestibility and retention of protein) in poultry, however, most authors conclude that the caeca do not have a significant influence on utilization of dietary protein or amino acid nutrition (Nesheim & Carpenter, 1967;Raharjo & Farrell, 1984;Salter & Coates, 1971;Salter, Coates & Hewitt, 1974;Salter & Fulford, 1974;Sibbald, 1979), although this depends on diet composition (Williams, 1995).…”

Section: Integrated Function In the Avian Gutmentioning

confidence: 99%

“…The hindgut (coprodeum, colon, caeca) of birds is capable of active sodium reabsorption and solute-linked water absorption (Braun, 2003;Laverty & Skadhauge, 1999;Singer, 2003;Thomas, 1982) and can thus modify both the composition and volume of refluxed urine. At least some water can be removed from hyperosmotic urine in birds (Skadhauge, 1980).…”

Section: The Role Of the Avian Gut In Salt And Water Regulationmentioning

confidence: 99%

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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%

Section: The Role Of the Avian Gut In Salt And Water Regulationmentioning

confidence: 99%

Section: Integrated Function In the Avian Gutmentioning

confidence: 99%

Section: The Role Of the Avian Gut In Salt And Water Regulationmentioning

confidence: 99%

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The integration of digestion and osmoregulation in the avian gut

2009

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“…Dit wordt gedaan door een hogere reabsorptie van water in de nieren en in de darm, waardoor de mest en urine minder water bevatten (Laverty and Skadhauge, 1999). Verzameling van excreta kan daarom een methode zijn om dehydratatie vast te stellen.…”

Section: De Excretaunclassified

Risicobeoordeling waterverstrekking aan vleeskuikens en vleeskuikenouderdieren

Jong

Koene

Ellen

et al. 2016

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Osmoregulation and Excretion

Larsen

Deaton

Onken

et al. 2014

Comprehensive Physiology

179

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The article discusses advances in osmoregulation and excretion with emphasis on how multicellular animals in different osmotic environments regulate their milieu intérieur. Mechanisms of energy transformations in animal osmoregulation are dealt with in biophysical terms with respect to water and ion exchange across biological membranes and coupling of ion and water fluxes across epithelia. The discussion of functions is based on a comparative approach analyzing mechanisms that have evolved in different taxonomic groups at biochemical, cellular and tissue levels and their integration in maintaining whole body water and ion homeostasis. The focus is on recent studies of adaptations and newly discovered mechanisms of acclimatization during transitions of animals between different osmotic environments. Special attention is paid to hypotheses about the diversity of cellular organization of osmoregulatory and excretory organs such as glomerular kidneys, antennal glands, Malpighian tubules and insect gut, gills, integument and intestine, with accounts on experimental approaches and methods applied in the studies. It is demonstrated how knowledge in these areas of comparative physiology has expanded considerably during the last two decades, bridging seminal classical works with studies based on new approaches at all levels of anatomical and functional organization. A number of as yet partially unanswered questions are emphasized, some of which are about how water and solute exchange mechanisms at lower levels are integrated for regulating whole body extracellular water volume and ion homeostasis of animals in their natural habitats. © 2014 American Physiological Society.

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Physiological roles and regulation of transport activities in the avian lower intestine

Cited by 18 publications

References 84 publications

The integration of digestion and osmoregulation in the avian gut

The integration of digestion and osmoregulation in the avian gut

Risicobeoordeling waterverstrekking aan vleeskuikens en vleeskuikenouderdieren

Osmoregulation and Excretion

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