Response of the Somali donkey to dehydration: hematological changes

Maloiy, Gmo; Boarer, C. D. H.

doi:10.1152/ajplegacy.1971.221.1.37

Cited by 26 publications

(9 citation statements)

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“…Moreover, in a similar manner to the goats, the osmotic changes in the blood of the rehydrated camel were of low magnitude (Yagil et al 1974;Hoppe et al 1976; Schroter, Zine Filali, Brain, Jeffry & Robertshaw, 1990). The same is true also for the donkey, Zebu cattle (Maloiy & Boarer, 1971), sheep (Blair-West et al 1980) and in non-desert goats (Silanikove, 1991). Despite the slight changes in plasma osmolality and haematocrit following rehydration, it has been concluded that there is rapid absorption of water in the rehydrated camel (Yagil et al 1974;Etzion et al 1984).…”

Section: Evolution Of Theories Regarding the Homeostatic Responses Tomentioning

confidence: 91%

“…In addition to ruminants, in the second group belong the donkey, capable of losing 20% of its mass during dehydration, the dog and the horse, capable of losing 10-12 % of their mass. These animals do not have a rumen, yet their blood is diluted much less than might be expected from the equilibration of the water ingested with their systemic fluid (Maloiy & Boarer, 1971;Thrasher et al 1984;Sneddon, Van Der Walt & Mitchell, 1992).…”

Section: Co/nchisiansmentioning

confidence: 99%

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The struggle to maintain hydration and osmoregulation in animals experiencing severe dehydration and rapid rehydration: the story of ruminants

Silanikove¹

1994

Experimental Physiology

127

110

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Ruminants in tropical and desert areas routinely experience cycles of severe dehydration and rapid rehydration. These animals can withstand severe dehydration (18‐40% of initial body weight), which exceeds considerably the capacity of most monogastric mammals. This capacity is related to their ability to use, during the course of dehydration, their large water reservoir in the rumen, which contributes 50‐70% of the total water loss. As rumen fluid is in approximate isotonicity with systemic fluid, the utilization of gut water during the course of dehydration involves a considerable load of sodium and potassium. Consequently, the effectiveness of utilization of rumen fluid during dehydration depends on the capacity of the kidney to ‘desalt’ the water absorbed from the gut and on maintenance of salivary flow to the rumen. Following rehydration, ruminants can imbibe their entire water deficit in one drinking and the entire amount ingested is first retained in the rumen. The rumen volume at this stage may exceed the extracellular fluid volume and the sudden drop in rumen osmolality creates a huge osmotic gradient (200‐300 mosmol kg‐1) between the rumen and systemic fluid. Ruminant animals are confronted at this stage by two opposing tasks, each of them of vital importance: (i) the need to prevent the osmotic hazard leading to water intoxication; and (ii) the need to retain the ingested water, so that it is not missing for the next dehydration cycle. The most prevalent view until recently was a theory which attributes an osmotic protective mechanism to the rumen wall. However, such a capacity has not yet been demonstrated and is challenged by contradictory observations that large amounts of water are absorbed from the rumen following rehydration. The view that is most consistent with available information is that gustatory‐alimentary and hepatoportal signals regarding the presence of large amounts of water in the rumen and the absorption of water from the gut activate a range of homeostatic responses involved in fluid and sodium restitution. The efferent elements, presumably activated by the CNS, include: a dramatic increase in secretion of hypotonic saliva and, reciprocally, a dramatic drop in urine flow. The enhanced saliva secretion recycles a considerable portion of the water absorbed from the gut back to the rumen, which allows effective retention of water while avoiding the danger of osmotic threat to the red blood cells. The enhanced saliva secretion also drains large amounts of sodium and bicarbonate from the blood. Accompanying responses are marked retention of sodium and carbonic acid in the kidney.(ABSTRACT TRUNCATED AT 400 WORDS)

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Section: Evolution Of Theories Regarding the Homeostatic Responses Tomentioning

confidence: 91%

Section: Co/nchisiansmentioning

confidence: 99%

The struggle to maintain hydration and osmoregulation in animals experiencing severe dehydration and rapid rehydration: the story of ruminants

Silanikove¹

1994

Experimental Physiology

127

110

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“…The significantly reduced PCV values of the elephants from MEF compared to the elephants from NZG and PEO could be due to the fact that the elephants kept at MEF have more opportunities to keep themselves hydrated. Dehydration has been shown to be a promoting factor of high PCV values (Maloiy & Boarer 1971). The elephants from MEF during their many walks come regularly to the waterway and this provides them with ample opportunity to drink and sprinkle water on their bodies.…”

Section: Funding: Nonementioning

confidence: 99%

A comparative haematological analysis of Asian Elephants Elephas maximus Linnaeus, 1758 (Mammalia: Proboscidea: Elephantidae) managed under different captive conditions in Sri Lanka

Mel¹,

Weerakoon²,

Ratnasooriya³

et al. 2014

J. Threat. Taxa

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“…Water requirements Maloiy and Boarer (1971) carried out an experiment to compare the ability of donkeys and Zebu cattle to tolerate dehydration. These authors concluded that donkeys were only slightly more able to tolerate long-term water deprivation than Zebu cattle, having more controlled restoration of plasma osmolarity and better water conservation than cattle but otherwise having similar haematological changes.…”

Section: Energeticsmentioning

confidence: 99%

“…These authors concluded that donkeys were only slightly more able to tolerate long-term water deprivation than Zebu cattle, having more controlled restoration of plasma osmolarity and better water conservation than cattle but otherwise having similar haematological changes. Maloiy and Boarer (1971) place donkeys nearer to cattle than to camels in their ability to tolerate dehydration: similar to goats and sheep. In comparisons of the faecal dry matter content of waterdeprived African herbivores and their non-deprived conspeci¢cs, Maloiy and colleagues (1978) found that the biggest di¡erence was in donkeys and camels, while there was little di¡erence in cattle, goats and sheep.…”

Section: Energeticsmentioning

confidence: 99%

A Review of the Factors Affecting the Survival of Donkeys in Semi-arid Regions of Sub-Saharan Africa

Smith

Pearson²

2005

Trop Anim Health Prod

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The large fluctuations seen in cattle populations during periods of drought in sub-Saharan Africa are not evident in the donkey population. Donkeys appear to have a survival advantage over cattle that is increasingly recognized by smallholder farmers in their selection of working animals. The donkey's survival advantages arise from both socioeconomic and biological factors. Socioeconomic factors include the maintenance of a low sustainable population of donkeys owing to their single-purpose role and their low social status. Also, because donkeys are not usually used as a meat animal and can provide a regular income as a working animal, they are not slaughtered in response to drought, as are cattle. Donkeys have a range of physiological and behavioural adaptations that individually provide small survival advantages over cattle but collectively may make a large difference to whether or not they survive drought. Donkeys have lower maintenance costs as a result of their size and spend less energy while foraging for food; lower energy costs result in a lower dry matter intake (DMI) requirement. In donkeys, low-quality diets are digested almost as efficiently as in ruminants and, because of a highly selective feeding strategy, the quality of diet obtained by donkeys in a given pasture is higher than that obtained by cattle. Lower energy costs of walking, longer foraging times per day and ability to tolerate thirst may allow donkeys to access more remote, under-utilized sources of forage that are inaccessible to cattle on rangeland. As donkeys become a more popular choice of working animal for farmers, specific management practices need to be devised that allow donkeys to fully maximize their natural survival advantages.

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Response of the Somali donkey to dehydration: hematological changes

Cited by 26 publications

References 0 publications

The struggle to maintain hydration and osmoregulation in animals experiencing severe dehydration and rapid rehydration: the story of ruminants

The struggle to maintain hydration and osmoregulation in animals experiencing severe dehydration and rapid rehydration: the story of ruminants

A comparative haematological analysis of Asian Elephants Elephas maximus Linnaeus, 1758 (Mammalia: Proboscidea: Elephantidae) managed under different captive conditions in Sri Lanka

A Review of the Factors Affecting the Survival of Donkeys in Semi-arid Regions of Sub-Saharan Africa

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