Sex and storage affect cholinesterase activity in blood plasma of Japanese quail

Blood plasma cholinesterase (ChE) activity is a sensitive indicator of exposure to organophosphorus and carbamate insecticides. Effects of sex and storage of samples were studied as sources of variability by treating breeding Japanese quail (Coturnix japonica) with 3 mg of dicrotophos or carbofuran per kg of body weight and comparing blood plasma ChE activities for samples collected at 1 hr postdosage and assayed fresh, after 1 and 2 days of refrigeration (4 C), and after 1, 7 and 28 days of freezing (-25 C). ChE activity of fresh control plasma was 34% (P less than 0.01) higher in males than females. Male ChE activity remained essentially unchanged during storage while female ChE activity increased (P less than 0.05) gradually over time under both storage conditions. In contrast, when plasma ChE activity was inhibited by either antiChE, male plasma ChE activity was depressed further than female ChE (P less than 0.01) and remained constant during storage while female ChE activity continued to decrease (P less than 0.05). These divergent effects of exposure to antiChE compounds and sample storage indicate extreme care should be exercised in use of blood plasma for evaluation of antiChE exposure in wild birds.     

Effects of long-term dehydration on oxidative stress,apoptotic markers and neuropeptides in the gastric mucosa of the dromedary camel

We investigated the effects of 20 days of dehydration and 20 days of dehydration followed by 72 h of rehydration on the gastric mucosa of the one-humped dromedary camel. The parameters addressed include biomarkers of oxidative stress, apoptosis, gastric epithelial histology, gastric neuropeptides, and their receptors. Nineteen clinically healthy, 4–5 year-old male dromedary camels were divided into three groups (five control camels, eight dehydrated for 20 days, six dehydrated for 20 days and then rehydrated for 72 h). Dehydration affected the oxidative stress biomarkers causing a significant increase in malondialdehyde, glutathione, nitric oxide, and catalase values compared with controls. Also the results revealed that dehydration caused different size cellular vacuoles and focal necrosis in the gastric mucosa. Rehydration for 72 h resulted in improvement in some parameters but was not enough to fully abolish the effect of dehydration. Dehydration caused significant increase in apoptotic markers; tumor necrosis factor α, caspases 8 and 3, BcL-x1 and TGFβ whereas caspase 9, p53, Beclin 1, and PARP1 showed no significant change between the three groups indicating that apoptosis was initiated by the extrinsic pathway. Also there were significant increases in prostaglandin E2 receptors and somatostatin in plasma and gastric epithelium homogenate, and a significant decrease in cholecystokinin–8 receptors. A significant decrease of hydrogen potassium ATPase enzyme activity was also observed. Pepsinogen C was not affected by dehydration. It is concluded that long-term dehydration induces oxidative stress and apoptosis in camel gastric mucosa and that camels adjust gastric functions during dehydration towards water economy. More than 72 h are needed before all the effects of dehydration are reversed by rehydration.

     

Effects of dehydration on plasma osmolality, thirst-related behavior, and plasma and brain angiotensin concentrations in Couch's spadefoot toad, Scaphiopus couchii

Under dehydrating conditions, many terrestrial vertebrates species exhibit increases in plasma osmolality and their drinking behavior. Under some circumstances, this behavioral change is accompanied by changes in plasma and central angiotensin concentrations, and it has been proposed that these changes in angiotensin levels induce the thirst-related behaviors. In response to dehydration, the spadefoot toad, Scaphiopus couchii, exhibits thirst-related behavior in the form of cutaneous drinking. This behavior has been termed water absorption response (WR) behavior. Spadefoot toads live in harsh desert environments and are subject annually to dehydrating conditions that may induce thirst-related behavior. We tested the hypothesis that an increase in WR behavior is associated with both an increase in plasma osmolality and an increase in plasma and brain angiotensin concentrations. First, we determined the degree of dehydration that was necessary to initiate WR behavior. Animals dehydrated to 85% of their standard bladder-empty weight via deprivation of water exhibited WR behavior more frequently than control toads left in home containers with water available. Next, using the same dehydration methods, we determined the plasma osmolality and sodium concentrations of dehydrated toads. Toads dehydrated to 85% standard weight also had a significant increase in plasma osmolality, but exhibited no overall change in plasma sodium concentrations, indicating that while an overall increase in plasma osmolality appears to be associated with WR behavior in S. couchii, changes in sodium concentrations alone are not sufficient to induce the behavior. Finally, plasma and brain angiotensin concentrations were measured in control toads and toads dehydrated to 85% standard weight. Plasma and brain angiotensin concentrations did not increase in dehydrated toads, indicating that dehydration-induced WR behavior that is associated with changes in plasma osmolality may not be induced by changes in endogenous angiotensin concentrations in S. couchii.     

Differential effects of water and saline intake on water deprivation-induced c-Fos staining in the rat

We studied c-Fos staining in adult male rats after 48 h of water deprivation and after 46 h of water deprivation with 2 h of access to water or physiological saline. Controls were allowed ad libitum access to water and physiological saline. For immunocytochemistry, anesthetized rats were perfused with a commercially available antibody for c-Fos. Dehydration significantly increased plasma vasopressin (AVP), osmolality, plasma renin activity (PRA), hematocrit, and sodium concentration and decreased urinary volume. Fos staining was significantly increased in the median preoptic nucleus, organum vasculosum of the lamina terminalis, supraoptic nucleus (SON), and magnocellular and parvocellular paraventricular nucleus (PVN), as well as the area postrema, nucleus of the solitary tract (NTS), and rostral ventrolateral medulla (RVL). Rehydration with water significantly decreased AVP levels and Fos staining in the SON, PVN, and RVL and significantly increased Fos expression in the perinuclear zone of the SON, NTS, and parabrachial nucleus. Rehydration with water was associated with decreased urinary sodium concentration and hypotonicity, and hematocrit and PRA were comparable to levels seen after dehydration. After rehydration with saline, plasma osmolality, hematocrit, and PRA were not different from control, but plasma AVP and urinary sodium concentration were increased. In the SON, Fos staining was significantly increased, with a great percentage of the Fos cells also stained for oxytocin compared with water deprivation. Changes in Fos staining were also observed in the NTS, RVL, parabrachial nucleus, and PVN. Rehydration with water or saline produces differential effects on plasma AVP, Fos staining, and sodium concentration.     

Tissue norepinephrine turnover and cardiovascular responses during intermittent dehydration in the rat.

We investigated the central and peripheral sympathetic responses to intermittent dehydration in rats. The norepinephrine (NE) turnover, a biochemical index correlated with noradrenergic neuronal activity, was measured. The modification of blood pressure was also determined by telemetry during the different cycles of dehydration. Dehydration caused a decrease of NE turnover in A2, A5 and A6 nuclei and in peripheral organs. The vasopressinergic level of dehydrated rats decreased in hypophysis and hypothalamus, and increased in plasma. A repeated gradual increase of arterial blood pressure during the first three days of dehydration, followed by a sudden drop when the rats were rehydrated on the fourth day was observed. In conclusion, our study revealed an increase in blood pressure and in central sympathetic activity during dehydration.     

Cytological and physiological changes in recalcitrant Chinese fan palm (<Emphasis Type="Italic">Livistona chinensis</Emphasis>) embryos during cryopreservation

Cytological and physiological changes during cryopreservation were investigated in Livistona chinensis embryos excised 42 weeks after flowering. Both dehydration and freezing caused numerous cellular ultrastructural alterations. Dehydration seriously impaired plasma membrane integrity, while freezing caused a further increase in electrolyte leakage. Damage to cellular ultrastructure and plasmalemma integrity had an inverse relationship with water content in unfrozen embryos and a positive relationship in frozen embryos. Changes in activity of antioxidant enzymes differed during cryopreservation. Dehydration and freezing had little effect on superoxide dismutase activity, although these treatments greatly reduced embryo viability. Activity of dehydroascorbate reductase (DHAR) and glutathione reductase (GR) changed only slightly during dehydration, but dehydration markedly decreased activity of ascorbate peroxidase (APX) and catalase (CAT). Freezing further decreased APX and GR activity but increased CAT activity in dehydrated samples. A novel DHAR isozyme was induced during the freeze–thaw cycle. Membrane lipid peroxidation was detected in the control embryos, and was promoted by both dehydration and freezing. The malondialdehyde (MDA) content in post-thaw embryos increased by a maximum of 30%. Thus, changes in viability of embryos were closely related to damage to cellular ultrastructure and plasmalemma integrity, but were not directly related to antioxidant activity nor MDA accumulation.     

Effects of water restriction during growth and adulthood on renal function of bobwhite quail,Colinus virginianus

Renal function and osmoregulation were studied in bobwhite quail (Colinus virginianus) raised with unrestricted water (chronically unrestricted group) or restricted water (chronically restricted group). There was no difference in urine concentrating ability between adult and juvenile (3.5 or 7.5 week-old) quail. A filtration marker (polyethylene glycol) was infused into adult quail via osmotic minipumps and responses to the following regimens studied: ad libitum water intake, short-term (4-day) water restriction, and acute (1-day) dehydration (withdrawal of all drinking water). Chronically restricted quail had higher urine-to-plasma ratios of polyethylene glycol and lower urine flow rates during short-term restriction. A greater proportion of the reduction in urine flow rate during dehydration was attributable to enhanced tubular reabsorption, rather than reduced rates of filtration, in chronically restricted than in chronically unrestricted birds. Chronically restricted birds also had higher maximum urine-to-plasma ratios of polyethylene glycol (but not higher urine osmolality). These differences occurred in the face of arginine vasotocin concentrations that were not different in the two groups of birds (approximately 15 pg·ml^-1 during hydration, and 45 pg·ml^-1 during water restriction or dehydration). These observations suggest that chronically restricted quail have an enhanced responsiveness of tubular reabsorption to dehydration, a finding consistent with previous observations of tubule hypertrophy and hyperplasia in these birds (Goldstein and Ellis 1991). Despite this, no difference was found in medullary cAMP levels, either basal or arginine vastotocin-or forskolin-stimulated, in the two groups. When given water ad libitum, chronically restricted quail drank copiously (more than two times the drinking rate of chronically unrestricted birds rehydrating from acute dehydration or short-term water restriction), but glomerular filtration rate, hematocrit, and plasma osmolality did not differ in the two groups under this condition; chronically restricted quail excreted the excess water consumed during rehydration in a copious urine accomplished by reduced tubular water reabsorption.Abbreviations ADH antidiuretic hormone - AVT arginine vasotocin - m_b body mass - cAMP cyclic adenosine-monophosphate - DEH birds raised with restricted water intake - dpm decays per minute - ECF extracellular fluid - ECFV extracellular fluid volume - E _PEG total rate of polyethylene glycol excretion - GFR glomerular filtration rate - Hct hematocrit - HYD birds raised with unrestricted water intake - PEG polyethylene glycol - P _osm plasma osmolality - P _PEG plasma concentration of polyethylene glycol - U _PEG urine concentration of polyethylene glycol - (U/P)_PEG urine-to-plasma ratio concentration of polycthylene glycol - V urine flow rate     

Elevation of the panting threshold of the desert iguana,Dipsosaurus dorsalis,during dehydration: Potential roles of changes in plasma osmolality and body fluid volume

Summary Dehydration of the desert iguana,Dipsosaurus dorsalis, resulted in a progressive elevation in the magnitude of the skin temperature necessary to elicit thermal panting (i.e., the panting threshold). Panting threshold increased from 43.4±0.8 °C at 100% initial body weight (IBW) to 45.4±1.2 °C at 90% IBW to 45.7±0.9 °C at 80% IBW. Plasma osmolality showed no significant change with dehydration to 80% IBW. Changes in plasma osmolality, whether induced by NaCl or non-ionic sucrose loading, had a significant impact on panting threshold. Increasing plasma osmolality resulted in an elevation of panting threshold while decreasing plasma osmolality resulted in lower panting thresholds. Decreasing body fluid volume by exsanguination of 1 ml whole blood/100 g body weight resulted in a mean increase in panting threshold by 0.7±0.2 °C. Volume loading with 160 mM NaCl (approximately isosmotic) had no significant effect on panting threshold. These data suggest that plasma osmolality and decreases in body fluid volume may be potent modulators of panting threshold during periods of water deprivation. However, at least in desert iguanas, increases in plasma osmolality would not appear to be an important factor in the elevation of panting threshold during dehydration to 80% IBW.     

Enhanced central response to dehydration in mice lacking angiotensin AT(1a) receptors

The objective was to determine the central nervous system (CNS) responses to dehydration (c-Fos and vasopressin mRNA) in mice lacking the ANG AT(1a) receptor [ANG AT(1a) knockout (KO)]. Control and AT(1a) KO mice were dehydrated for 24 or 48 h. Baseline plasma vasopressin (VP) was not different between the groups; however, the response to dehydration was attenuated in AT(1a) KO (24 +/- 11 vs. 10.6 +/- 2.7 pg/ml). Dehydration produced similar increases in plasma osmolality and depletion of posterior pituitary VP content. Neuronal activation was observed as increases in c-Fos protein and VP mRNA. The supraoptic responses were not different between groups. In the paraventricular nucleus (PVN), c-Fos-positive neurons (57.4 +/- 10.7 vs. 98.4 +/- 7.4 c-Fos cells/PVN, control vs. AT(1a) KO) and VP mRNA levels (1.0 +/- 0.1 vs. 1.4 +/- 0.1 microCi, control vs. AT(1a) KO) were increased with greater responses in AT(1a) KO. A comparison of 1- to 2-day water deprivation showed that plasma VP, brain c-Fos, and VP mRNA returned toward control on day 2, although plasma osmolality remained high. Data demonstrate that AT(1a) KO mice show a dichotomous response to dehydration, reduced for plasma VP and enhanced for PVN c-Fos protein and VP mRNA. The results illustrate the importance of ANG AT(1a) receptors in the regulation of osmotic and endocrine balance.     

Characterization of plasma cholinesterase activity in the Eurasian Griffon Vulture Gyps fulvus and its in vitro inhibition by carbamate pesticides

The legal and illegal use of organophosphorus and carbamate pesticides represents one of many threats to birds. The activity of the cholinesterase enzyme in plasma is used as a non‐destructive biomarker to diagnose the exposure of birds to these pesticides. Scavengers are one of the most important bird groups threatened by the use of baits poisoned with anticholinesterase pesticides. Knowledge of the characteristics of this enzyme in each bird species is crucial, as several studies indicate that more than one cholinesterase form may be present in the plasma of birds. In this study, cholinesterase activity was characterized in the plasma of the Eurasian Griffon Vulture Gyps fulvus by using several substrates and inhibitors of the enzyme, and its normal activity value was also determined. The in vitro sensitivity of Gyps fulvus plasma cholinesterase to carbamate insecticides (aldicarb, carbaryl and methomyl) was also investigated. The results indicated that propionylthiocholine iodide was the preferred substrate to determine plasma cholinesterase activity, followed by acetylcholine iodide and S‐butyrylcholine iodide, and acetylcholinesterase was the predominant enzymatic activity in Gyps fulvus plasma. Aldicarb was the most potent in vitro inhibitor of plasma cholinesterase activity in this species. However, cholinesterase enzymatic activity was significantly inhibited by all tested carbamates, providing further evidence that this biomarker is a suitable tool to monitor the exposure to these poisons in the field, highlighting its utility in conservation programmes.     

Method of ethanol administration as a confounding factor in studies of fetal alcohol syndrome

Female Sprague-Dawley rats were fed a complete liquid diet containing either 5.5% ethanol (mean daily intake of about 9g of ethanol per kg body weight) or an isocaloric amount of dextrose (control group), with additional water available $\text{ad}$$\text{libitum}$. The diets were fed for four weeks prior to and throughout pregnancy. On day 20 of gestation cardiac output and blood flow to the placeta, heart, kidneys and uterus were measured and plasma osmolality and muscle dry weight were determined. No significant differences were seen between alcohol and control groups with respect to litter size, fetal weight, maternal cardiac output, blood flow to the placenta or other organs, plasma osmolality, or muscle dry weight. This contrasts with previous experiments in which a similar quantity of alcohol (as % calories) was offered in drinking water (equivalent to a mean daily ethanol intake of 10g/kg body weight). Under those conditions fetal weight was reduced, blood flow to the plascenta was reduced, and plasma osmolality and muscle dry weight were increased, indicating a moderate degree of dehydration. It is concluded that the effect of ethanol ingestion is influenced by the mode of administration of the ethanol. Dehydration may be a confounding factor in studies of animal models of fetal alcohol syndrome, although it is not possible to rule out a differential metabolic response to alcohol, depending on the mode of administration.     

Contributions of the kidneys and intestines to water conservation,and plasma levels of antidiuretic hormone,during dehydration in house sparrows (Passer domesticus)

Summary The contributions of the kidneys, the small intestine and the lower intestine (rectum plus cloaca) to water conservation during dehydration in unanaesthetized, unrestrained house sparrows (Passer domesticus) were assessed. Thirty hours of acute dehydration resulted in a 12% loss in body mass and a significant increase in plasma osmolality. Glomerular filtration rate declined by 55%, from 7.7 to 3.5 ml/h, and urine flow rate delined by more than 80%, from 0.2 to 0.03 ml/h. These changes are likely attributable to a large increase in plasma levels of arginine vasotocin during dehydration, from <26 pg/ml in hydrated birds to greater than 200 pg/ml after 30 h dehydration. Flow of water from the ileum to the lower intestine was reduced during dehydration, primarily because of a reduced flow of dry matter (with no significant reduction in water content). The rate of water loss in the excreta declined from 0.2 ml/h in hydrated birds to 0.04 ml/h in dehydrated birds. The rate of water reabsorption in the lower intestine (equal to the rate of water loss in the excreta minus the combined rates of inflow into the lower intestine from the urine and the ileal contents) slightly exceeded the rate of water flow from the ileum in both hydrated and dehydrated birds. We suggest that much of the water reabsorbed in the lower intestine of hydrated birds derives from the urine, but that primarily water from ileal contents is reabsorbed in dehydrated birds. That is, urine undergoes significant post-renal modification in hydrated but not dehydrated house sparrows.     

Renal function and organic anion and cation transport during dehydration and/or food restriction in chickens

The effect of dehydration in the presence or absence of continued food intake on renal function was evaluated in chickens. In addition, renal transport of organic anions and cations under these conditions was assessed in vitro by uptake of ¹⁴C-para-aminohippuric acid and ¹⁴C-tetraethylammonium bromide by renal slices. Water restriction with continued food intake resulted in increases in serum osmolality and serum concentrations of sodium, uric acid, calcium and total protein. If food was restricted in addition to water, only serum osmolality and sodium concentration were significantly increased after 48 hours. Dehydration with continued access to food resulted in marked decreases in extracellular fluid volume, glomerular filtration rate and effective renal plasma flow. If food was restricted during dehydration, the decrease in effective renal plasma flow was attenuated despite reductions in glomerular filtration rate and extracellular fluid comparable to that seen in dehydrated birds allowed free access to food. Transport of organic anions was significantly increased after 24 and 48 hours of water restriction, regardless of whether food was withheld. Enhanced transport of organic anions in the presence of decreased glomerular filtration rate and effective renal plasma flow during dehydration may promote precipitation of urates and nephrosis in chickens.Abbreviations cpm counts per minute - dpm disintegrations per minute - ECF extracellular fluid - ERPF effective renal plasma flow - GFR glomerular filtration rate - PAH para-aminohippuric acid - SEM standard error of the mean - TEA tetraethylammonium bromide     

Thermogenic drinking: mediation by osmoreceptor and angiotensin II pathways

Exposure of rats to air at 5 C for 1-12 days is accompanied by a relative dehydration in spite of the continued presence of water. Dehydration during exposure to cold was manifested by: 1) a reduction in the ratio of water/food ingested; 2) an increase in the ratio of urine excreted/water ingested; 3) an increased evaporative water loss; 4) an increased serum osmolality and chloride concentration; and 5) a striking thirst and ingestion of water after transfer from cold to air at 26 C. Drinking began within 15 min and lasted approximately 1 h. Thermogenic drinking persisted for at least 120 days of exposure to cold. It was not thwarted by preventing access to water for either 1 or 2 h after transfer to warm air, but either intragastric or intraperitoneal administration of a water load equal to 3% of body weight inhibited water intake after transfer. These characteristics of thermogenic drinking are similar to those observed after 24 h of dehydration at 26 C; they also suggest that the cold-exposed rat is dehydrated relative to controls. These results suggest that osmoreceptors may play a role in the induction of thermogenic drinking. However, angiotensin II receptors may also play a role. Thermogenic drinking was inhibited by a beta 2-adrenergic, but not a beta 1-adrenergic, antagonist as well as by captopril, an inhibitor of the conversion of angiotensin I to angiotensin II. Further, plasma renin activity increased fourfold within 15 min after removal from cold. This suggests that an additional component involved in thermogenic drinking is the angiotensin II receptor. The extent to which thermogenic drinking is mediated by each pathway is unknown and will require additional studies.     

Effect of hydration on plasma volume and endocrine responses to water immersion

To determine the effect of hydration on the early osmotic and intravascular volume and endocrine responses to water immersion the hematocrit, hemoglobin, plasma renin activity (PRA), and plasma electrolyte, aldosterone (PA), and vasopressin (PVP) concentrations were measured during immersion following 24-h dehydration; these were compared with corresponding values following rapid rehydration. Six men and one woman (age 23-46 yr) underwent 45 min of standing immersion to the neck preceded by 45-min standing without immersion, first dehydrated, and then 105 min later after rehydration with water. Immersion caused an isotonic expansion of the plasma volume (P less than 0.001), which occurred independently of hydration status. Suppression of PRA (P less than 0.001) and PA (P less than 0.001) during both immersions also occurred independently of hydration status. Suppression of plasma vasopressin was observed during dehydrated immersion (P less than 0.001) but not during rehydrated immersion. It is concluded that plasma tonicity is not a factor influencing PVP suppression during water immersion.     

Some effects of water deprivation on dorcas gazelle (Gazella dorcas) in the Sudan

1. The effects of dehydration for 10 days and subsequent rehydration for 2 days on some physiological and biochemical parameters were studied in the Dorcas gazelle. 2. At the end of the 10 days of dehydration, feed intake and body weight were decreased by 42 and 29% of the control values, respectively. Rehydration restored most of the loss in feed intake and body weight. 3. Dehydration decreased the water content in the faeces of the gazelles by 41%. Rehydration restored 36% of the lost faecal water. Urine volume in dehydrated animals decreased by 66%, an effect which was readily reversed by rehydration. 4. Blood haemoglobin of dehydrated gazelles decreased by 22% but this effect was not reversed by rehydration for 2 days. 5. Dehydration for 10 days decreased the concentration of serum glucose by 34% and increased that of urea and albumin by 34 and 18%, respectively. Dehydration for 2 days reversed these effects completely. 6. The serum concentrations of sodium, potassium and chloride were increased by dehydration by 23, 44 and 18% respectively. After 2 days of rehydration the values returned to normal. 7. No change in the heart rate, pulse or temperature was found during the dehydration period. 8. The gazelles survived the 10 days of dehydration, although they tended to be drowsy, weak and emaciated during the last 2 days of dehydration. The animals appeared normal after rehydration.     

Seawater drinking restores water balance in dehydrated harp seals

The purpose of this study was to answer the question of whether dehydrated harp seals (Phoca groenlandica) are able to obtain a net gain of water from the intake of seawater. Following 24 h of fasting, three subadult female harp seals were dehydrated by intravenous administration of the osmotic diuretic, mannitol. After another 24 h of fasting, the seals were given 1,000 ml seawater via a stomach tube. Urine and blood were collected for measurement of osmolality and osmolytes, while total body water (TBW) was determined by injections of tritiated water. In all seals, the maximum urinary concentrations of Na⁺ and Cl⁻ were higher than in seawater, reaching 540 and 620 mM, respectively, compared to 444 and 535 mM in seawater. In another experiment, the seals were given ad lib access to seawater for 48 h after mannitol-induced hyper-osmotic dehydration. In animals without access to seawater, the mean blood osmolality increased from 331 to 363 mOsm kg⁻¹ during dehydration. In contrast, the blood osmolality, hematocrit and TBW returned to normal when the seals were permitted ad lib access to seawater after dehydration. In conclusion, this study shows that harp seals have the capacity to gain net water from mariposa (voluntarily drinking seawater) and are able to restore water balance after profound dehydration by drinking seawater.     

Thermoregulatory responses and blood viscosity in dehydrated heat-exposed broilers (Gallus domesticus)

This study was to elucidate thermoregulation in dehydrated heat-exposed broilers. When broilers were dehydrated, heat production (HP), comb surface temperature (Tcs) and respiration rate (RR) decreased significantly. Conversely, rectal (Tr) and back skin (Tbs) temperatures, whole blood viscosity (WBV), haematocrit (HCT), plasma protein concentration (PPC) and plasma osmolality (PO) increased. During heat exposure, HP, WBV, HCT and PPC decreased significantly, while Tr, Tcs, Tbs and RR increased. The onset of panting against rectal temperature was delayed in dehydrated birds. These results suggest that dehydration leads to a lower blood volume, resulting in a decrease in blood flow to heat exchange organs and surfaces in broilers. This induces a lower sensible heat loss from extremities, a lower evaporative heat loss and a higher sensible heat loss from trunk, subsequent to regulate their body temperature at a higher level of deep body temperature.     

Plasma volume and electrolytes during progressive water deprivation in chickens (Gallus domesticus)

1. Studies were performed to examine the effects of progressive water deprivation in the fowl (Gallus domesticus). 2. A reduction in plasma volume and an increase in capillary permeability to protein were observed only after 3 or 4 days of dehydration. 3. Moderate changes in arterial blood pressure and heart rate were noted in dehydrated birds but respiratory rate and body temperature remained unchanged. 4. Dehydration was associated with increases in the concentration of total solutes, sodium and chloride in plasma but no changes were noted in plasma potassium levels or arterial pH. 5. The results indicate that the chicken can maintain volume more effectively during water deprivation than several mammalian species.