ORCID Profile
0000-0002-4746-4975
Current Organisation
University of Adelaide
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Animal Physiology—Systems | Comparative Physiology | Anatomy And Physiology | Physiology
Digestive system and disorders | Urogenital system and disorders | Global climate change adaptation measures |
Publisher: University of Chicago Press
Date: 03-2010
DOI: 10.1086/597524
Abstract: 3-O-methyl-D-glucose has been extensively used as a proxy for d-glucose uptake. This nonmetabolizable analog has lower affinity for transporters, potentially leading to underestimates of glucose absorption rates as well as overestimates of the nutritional significance of passive uptake. Here we sought to precisely quantify the bias, if any, incurred when using 3-O-methyl-D-glucose by comparing relative absorption rates with D-glucose in vivo in a seasonally frugivorous bird, the American robin. By simultaneously administering these D-glucose probes with L-glucose--the latter absorbed only via nonmediated mechanisms and the former absorbed by both mediated and nonmediated mechanisms--using common pharmacokinetic procedures, we were able to estimate the nutritional significance of paracellular uptake in this species. The relative absorption rate of 3-O-methyl-D-glucose calculated over the initial absorptive phase was not significantly different from that of D-glucose, indicating that the former provides reasonable estimates of glucose absorption rates in vivo. The ratio of L-glucose to D-glucose cumulative fractional absorption indicates that around 60% of total glucose absorption in American robins is paracellular and showed no apparent bias in using 3-O-methyl-D-glucose when averaged over the entire initial absorptive phase. Although the absorption and elimination kinetics of radiolabeled D-glucose were appropriate for pharmacokinetic analysis in this study, because of the potential for interspecific differences in loss to catabolism, it should be used in vivo with caution and with independent verification of absorption efficiency.
Publisher: The Company of Biologists
Date: 15-05-2007
DOI: 10.1242/JEB.02766
Abstract: Two decades ago D. J. Keegan reported results on Egyptian fruit bats(Rousettus aegyptiacus, Megachiroptera) that were strangely at odds with the prevailing understanding of how glucose is absorbed in the mammalian intestine. Keegan's in vitro tests for glucose transport against a concentration gradient and with phloridzin inhibition in fruit bat intestine were all negative, although he used several different tissue preparations and had positive control results with laboratory rats. Because glucose absorption by fruit bats is nonetheless efficient, Keegan postulated that the rapid glucose absorption from the fruit bat intestine is not through the enterocytes, but must occur via spaces between the cells. Thus, we hypothesized that absorption of water-soluble compounds that are not actively transported would be extensive in these bats, and would decline with increasing molecular mass in accord with sieve-like paracellular absorption. We did not presume from Keegan's studies that there is no Na+-coupled, mediated sugar transport in these bats, and our study was not designed to rule it out, but rather to quantify the level of possible non-mediated absorption. Using a standard pharmacokinetic technique, we fed,or injected intraperitonealy, the metabolically inert carbohydrates l-rhamnose (molecular mass=164 Da) and cellobiose (molecular mass=342 Da), which are absorbed by paracellular uptake, and 3-O-methyl-d-glucose (3OMd-glucose), a d-glucose analog that is absorbed via both mediated(active) and paracellular uptake. As predicted, the bioavailability of paracellular probes declined with increasing molecular mass (rhamnose,62±4% cellobiose, 22±4%) and was significantly higher in bats than has been reported for rats and other mammals. In addition, fractional absorption of 3OMd-glucose was high (91±2%). We estimated that Egyptian fruit bats rely on passive, paracellular absorption for the majority of their glucose absorption (at least 55% of 3OMd-glucose absorption), much more than in non-flying mammals.
Publisher: The Company of Biologists
Date: 12-2004
DOI: 10.1242/JEB.01238
Abstract: Small nectarivorous vertebrates face a quandary. When feeding, they must eliminate prodigious quantities of water however, when they are not feeding,they are susceptible to dehydration. We examined the role of the kidney in the resolution of this osmoregulatory dilemma. Broad-tailed hummingbirds(Selasphorus platycercus) displayed diurnal variation in glomerular filtration rate (GFR). During the morning, midday and evening, GFRs were 0.9±0.6, 1.8±0.4 and 2.3±0.5 ml h–1,respectively. At midday, GFR increased linearly with increased water intake. During the evening, hummingbirds decreased renal fractional water reabsorption linearly with increased water intake. Broad-tailed hummingbirds appeared to cease GFR at night (–0.1±0.2 ml h–1) and decreased GFR in response to short-term (∼1.5 h) water deprivation. GFR seems to be very responsive to water deprivation in hummingbirds. Although hummingbirds and other nectarivorous birds can consume astounding amounts of water, a phylogenetically explicit allometric analysis revealed that their diurnal GFRs are not different from the expectation based on body mass.
Publisher: Frontiers Media SA
Date: 27-05-2022
DOI: 10.3389/FVETS.2022.894146
Abstract: Hyperthermia is a performance and welfare issue for exercising horses. The thermoregulatory stressors associated with exercise have typically been estimated by responses in the laboratory. However, monitoring surface skin temperature (T sk ) coincident with core temperature (T c ) has not previously been investigated in horses exercising in the field. We investigated the suitability of monitoring surface T sk as a metric of the thermoregulatory response, and simultaneously investigated its relationship with T c using gastrointestinal (GI) temperature. We evaluated T sk in 13 endurance horses competing during four endurance rides over 40 km ( n = 1) or a total of 80 km ( n = 12) distance. Following each 40-km loop, the horses were rested for 60 min. T sk and T c were continuously recorded every 15 s by an infrared thermistor sensor located in a modified belt and by telemetric GI pill, respectively, and expressed as mean ± SD. The net area under the curve (AUC) was calculated to estimate the thermoregulatory response to the thermal load of T sk over time (°C × minutes) using the trapezoidal method. The relationship between T sk and T c was assessed using scatterplots, paired t -test or generalized linear model ANOVA (delta T sk ) ( n = 8). Ambient temperature ranged from 6.7°C to 18.4°C. No relationship was found between T sk and T c profiles during exercise and recovery periods, and no significant difference between delta T sk results was detected when comparing exercise and rest. However, time to maximum T sk (67 min) was significantly reduced compared to T c (139 min) ( p = 0.0004) with a significantly lesser maximum T sk (30.3°C) than T c (39°C) ( p = 0.0002) during exercise. Net AUC T sk was 1,164 ± 1,448 and −305 ± 388°C × minutes during periods of exercise and recovery, respectively. We conclude that T sk monitoring does not provide a reliable proxy for the thermoregulatory response and horse welfare, most probably because many factors can modulate T sk without directly affecting T c . Those factors, such as weather conditions, applicable to all field studies can influence the results of T sk in endurance horses. The study also reveals important inter-in idual differences in T sk and T c time profiles, emphasizing the importance of an in idualized model of temperature monitoring.
Publisher: Elsevier BV
Date: 05-2009
DOI: 10.1016/J.CBPB.2009.02.003
Abstract: The tropical agamid lizard, Lophognathus temporalis, has higher metabolic and feeding rates during the wet season compared to the dry season. Also, lizards from urban sites tend to be larger than those from natural sites, partly due to site differences in food availability. Therefore, we hypothesized that activity of membrane-bound intestinal enzymes and masses of organs related to digestion would differ both seasonally and between urban and natural sites. To test this, we measured activities of aminopeptidase-N (APN), maltase, and sucrase, as well as organ masses. APN activity (micromol min(-1) g(-1)) was highest in the middle portion of the intestine (section 2), followed by the proximal portion (section 1) and then the distal portion (section 3). Maltase activity was highest in section 1 and decreased distally. We detected some sucrase activity in section 1 but none in sections 2 or 3. We found similar enzyme activities within each section irrespective of site or season. However, total enzyme activities were higher during the wet season compared to the dry season for both urban and bush L. temporalis. Total wet season enzyme activity in urban and bush L. temporalis was greatest for APN (25.4 15.8 micromol min(-1) respectively), then maltase (3.9 3.6 micromol min(-1) respectively) and then sucrase (0.3 0.2 micromol min(-1) respectively). The higher total enzyme activities was the result of an increase in intestinal mass during the wet season.
Publisher: The Royal Society
Date: 27-09-2006
Abstract: Twenty years ago, the highest active glucose transport rate and lowest passive glucose permeability in vertebrates were reported in Rufous and Anna's hummingbirds ( Selasphorus rufus , Calypte anna ). These first measurements of intestinal nutrient absorption in nectarivores provided an unprecedented physiological foundation for understanding their foraging ecology. They showed that physiological processes are determinants of feeding behaviour. The conclusion that active, mediated transport accounts for essentially all glucose absorption in hummingbirds influenced two decades of subsequent research on the digestive physiology and nutritional ecology of nectarivores. Here, we report new findings demonstrating that the passive permeability of hummingbird intestines to glucose is much higher than previously reported, suggesting that not all sugar uptake is mediated. Even while possessing the highest active glucose transport rates measured in vertebrates, hummingbirds must rely partially on passive non-mediated intestinal nutrient absorption to meet their high mass-specific metabolic demands.
Publisher: University of Chicago Press
Date: 09-2010
DOI: 10.1086/650472
Abstract: The digestive system is the interface between the supply of food for an animal and the demand for energy and nutrients to maintain the body, to grow, and to reproduce. Digestive systems are not morphologically static but rather dynamically respond to changes in the physical and chemical characteristics of the diet and the level of food intake. In this article, we discuss three themes that affect the ability of an animal to alter digestive function in relation to novel substrates and changing food supply: (1) the fermentative digestion in herbivores, (2) the integration of cardiopulmonary and digestive functions, and (3) the evolution of dietary specialization. Herbivores consume, digest, and detoxify complex diets by using a wide variety of enzymes expressed by bacteria, predominantly in the phyla Firmicutes and Bacteroidetes. Carnivores, such as snakes that feed intermittently, sometimes process very large meals that require compensatory adjustments in blood flow, acid secretion, and regulation of acid-base homeostasis. Snakes and birds that specialize in simple diets of prey or nectar retain their ability to digest a wider selection of prey. The digestive system continues to be of interest to comparative physiologists because of its plasticity, both phenotypic and evolutionary, and because of its widespread integration with other physiological systems, including thermoregulation, circulation, ventilation, homeostasis, immunity, and reproduction.
Publisher: Proceedings of the National Academy of Sciences
Date: 27-11-2007
Abstract: Anecdotal evidence suggests that birds have smaller intestines than mammals. In the present analysis, we show that small birds and bats have significantly shorter small intestines and less small intestine nominal (smooth bore tube) surface area than similarly sized nonflying mammals. The corresponding % reduction in intestinal volume and hence mass of digesta carried is advantageous because the energetic costs of flight increase with load carried. But, a central dilemma is how birds and bats satisfy relatively high energy needs with less absorptive surface area. Here, we further show that an enhanced paracellular pathway for intestinal absorption of water-soluble nutrients such as glucose and amino acids may compensate for reduced small intestines in volant vertebrates. The evidence is that l -rhamnose and other similarly sized, metabolically inert, nonactively transported monosaccharides are absorbed significantly more in small birds and bats than in nonflying mammals. To broaden our comparison and test the veracity of our finding we surveyed the literature for other similar studies of paracellular absorption. The patterns found in our focal species held up when we included other species surveyed in our analysis. Significantly greater lification of digestive surface area by villi in small birds, also uncovered by our analysis, may provide one mechanistic explanation for the observation of higher paracellular absorption relative to nonflying mammals. It appears that reduced intestinal size and relatively enhanced intestinal paracellular absorption can be added to the suite of adaptations that have evolved in actively flying vertebrates.
Publisher: The Company of Biologists
Date: 15-11-2008
DOI: 10.1242/JEB.020644
Abstract: Efficient mechanisms of glucose absorption are necessary for volant animals as a means of reducing mass during flight: they speed up gut transit time and require smaller volume and mass of gut tissue. One mechanism that may be important is absorption via paracellular (non-mediated) pathways. This may be particularly true for nectarivorous species which encounter large quantities of sugar in their natural diet. We investigated the extent of mediated and non-mediated glucose absorption in red wattlebirds Anthochaera carunculata (Meliphagidae) and rainbow lorikeets Trichoglossus haematodus (Loriidae) to test the hypothesis that paracellular uptake accounts for a significant proportion of total glucose uptake in these species. We found that routes of glucose absorption are highly dynamic in both species. In lorikeets, absorption of l-glucose(non-mediated uptake) is slower than that of d-glucose (mediated and non-mediated uptake), with as little as 10% of total glucose absorbed by the paracellular pathway initially (contrasting previous indirect estimates of∼0%). Over time, however, more glucose may be absorbed via the paracellular route. Glucose absorption by both mediated and non-mediated mechanisms in wattlebirds occurred at a faster rate than in lorikeets, and wattlebirds also rely substantially on paracellular uptake. In wattlebirds, we recorded higher bioavailability of l-glucose (96±3%)compared with d-glucose (57±2%), suggesting problems with the in vivo use of radiolabeled d-glucose. Further trials with 3-O-methyl-d-glucose revealed high bioavailability in wattlebirds (90±5%). This non-metabolisable glucose analogue remains the probe of choice for measuring uptake rates in vivo, especially in birds in which absorption and metabolism occur extremely rapidly.
Publisher: Elsevier BV
Date: 03-2023
Publisher: MDPI AG
Date: 03-2021
DOI: 10.3390/BIRDS2010007
Abstract: It is currently unknown if current guidelines for collecting and interpreting blood corticosterone in flying birds can be extrapolated to penguins. It is also difficult to collect blood quickly without causing stress to a penguin. Therefore, immunoreactive fecal glucocorticoid metabolites (FGCMs) may be the most practical and minimally invasive way of monitoring the stress levels of penguins. This study investigated the reliability of FGCMs for monitoring stress levels in captive Humboldt Penguins (Spheniscus humboldti) at Jurong Bird Park, Singapore. Humboldt Penguin feces were randomly s led and pooled from the exhibit for 2 months. The penguins were restrained and transported on three separate occasions to simulate stressful events. The feces were analyzed using an enzyme immunoassay to measure corticosterone levels. There were significant increases lasting 3 to 7 days in the FGCM levels after a stressful event. This method was then used to test whether accelerometer vests used for behavior quantification caused stress responses in these birds. There was no significant difference in FGCMs between time periods with and without the accelerometer vests. The results indicated that FGCMs can be an accurate indication of capture-, restraint-, and transport-related stress in Humboldt Penguins, and that accelerometer vests do not appear to cause stress.
Publisher: American Veterinary Medical Association (AVMA)
Date: 07-2017
Abstract: OBJECTIVE To evaluate use of a telemetric gastrointestinal (GI) pill to continuously monitor GI temperature in horses at rest and during exercise and to compare time profiles of GI temperature and rectal temperature. ANIMALS 8 Standardbred horses. PROCEDURES Accuracy and precision of the GI pill and a rectal probe were determined in vitro by comparing temperature measurements with values obtained by a certified resistance temperature detector (RTD) in water baths at various temperatures (37°, 39°, and 41°C). Subsequently, both GI and rectal temperature were recorded in vivo in 8 horses over 3 consecutive days. The GI temperature was recorded continuously, and rectal temperature was recorded for 3.5 hours daily. Comparisons were made between GI temperature and rectal temperature for horses at rest, during exercise, and after exercise. RESULTS Water bath evaluation revealed good agreement between the rectal probe and RTD. However, the GI pill systematically underestimated temperature by 0.14°C. In vivo, GI temperature data were captured with minimal difficulties. Most data loss occurred during the first 16 hours, after which the mean ± SD data loss was 8.6 ± 3.7%. The GI temperature was consistently and significantly higher than rectal temperature with an overall mean temperature difference across time of 0.27°C (range, 0.22° to 0.32°C). Mean measurement cessation point for the GI pill was 5.1 ± 1.0 days after administration. CONCLUSIONS AND CLINICAL RELEVANCE This study revealed that the telemetric GI pill was a reliable and practical method for real-time monitoring of GI temperature in horses.
Publisher: University of Chicago Press
Date: 05-2014
DOI: 10.1086/675493
Abstract: Carbohydrate-rich mistletoe fruits are consumed by a wide range of avian species. Small birds absorb a large portion of water-soluble nutrients, such as glucose, via the paracellular pathway. d-xylose, a pentose monosaccharide, is abundant in some nectars and mistletoe fruits consumed by birds, and it has been suggested that it is most likely absorbed via the paracellular pathway in birds. We measured apparent assimilation efficiency ([Formula: see text]) and bioavailability (f) for d-xylose and d- and l-glucose in three frugivorous Australian bird species. Mistletoebirds, silvereyes, and singing honeyeaters showed significantly lower [Formula: see text] for d-xylose than for d-glucose. Across two diet sugar concentrations, silvereyes and singing honeyeaters significantly increased f of both l-glucose (a metabolically inert isomer of d-glucose commonly used to quantify paracellular uptake) and d-xylose on the more concentrated diet, probably because of increased gut processing time. By contrast, mistletoebirds (mistletoe fruit specialists) did not vary f of either sugar with diet concentration. Mistletoebirds also showed higher f for d-xylose than l-glucose and eliminated d-xylose more slowly than silvereyes and singing honeyeaters, demonstrating differences in the handling of dietary xylose between these species. Our results suggest that d-xylose may be absorbed by both mediated and nonmediated mechanisms in mistletoebirds.
Publisher: Informa UK Limited
Date: 02-01-2017
Publisher: The Company of Biologists
Date: 02-2010
DOI: 10.1242/JEB.040071
Abstract: Passerine birds migrating long distances arrive at stopover sites to refuel having lost as much as 50% of their initial body mass (mb), including significant losses to digestive organs that may serve as a reservoir of protein catabolised for fuel during flight. Birds newly arrived at a stopover show slow or no mb gain during the initial 2–3 days of a stopover, which suggests that energy assimilation may be limited by reduced digestive organs. Measurements of migrants and captive birds subjected to simulated migratory fasts have shown reductions in intestine mass, morphological changes to the mucosal epithelium, and reductions in food intake and assimilation rate upon initial refeeding. We found that blackcaps (Sylvia atricapilla, Linnaeus) newly arrived at a migratory stopover after crossing the Sahara and Sinai deserts had significantly increased paracellular nutrient absorption (non-carrier mediated uptake occurring across tight junctions between enterocytes) that may provide partial compensation for reduced digestive capacity resulting from changes to intestinal tissues. Indeed, newly arrived birds also had a slightly reduced capacity for absorption of a glucose analogue (3-O-methyl-d-glucose) transported simultaneously by both carrier-mediated and non-mediated mechanisms. Increased paracellular absorption coupled with extended digesta retention time may thus allow migratory blackcaps to maintain high digestive efficiency during initial stages of refuelling while digestive organs are rebuilt.
Publisher: University of Chicago Press
Date: 05-2000
DOI: 10.1086/316753
Abstract: Many nectar-feeding bird species decrease food intake when sugar concentration in food is increased. This feeding response can be explained by two alternative hypotheses: compensatory feeding and physiological constraint. The compensatory feeding hypothesis predicts that if birds vary intake to maintain a constant energy intake to match energy expenditures, then they should increase intake when expenditures are increased. Broad-tailed hummingbirds were presented with sucrose solutions at four concentrations (292, 584, 876, and 1,168 mmol L(-1)) and exposed to two environmental temperatures (10 degrees and 22 degrees C). Birds decreased volumetric food intake in response to sugar concentration. However, when they were exposed to a relatively sudden drop in environmental temperature and, hence, to an acute increase in thermoregulatory energy expenditures, they did not increase their rate of energy consumption and lost mass. These results support the existence of a physiological constraint on feeding intake. A simple chemical reactor model based on intestinal morphology and in vitro measurements of sucrose hydrolysis predicted observed intake rates closely. This model suggests that intestinal sucrose hydrolysis rates were near maximal and, thus, may have imposed limits to sugar assimilation. Although sugar assimilation was high (95%), the proportions of excreted sucrose, glucose, and fructose found in excreta differed significantly. The monosaccharides glucose and fructose were about eight and three times more abundant than sucrose, respectively. Broad-tailed hummingbirds are small high-altitude endotherms that face unpredictable weather and the energetic expense of premigratory fattening. Digestive processes have the potential to impose severe challenges to their energy budgets.
Publisher: The Company of Biologists
Date: 2017
DOI: 10.1242/JEB.161653
Abstract: Birds in the order Caprimulgiformes (nightjars and allies) have a remarkable capacity for thermoregulation over a wide range of environmental temperatures, exhibiting pronounced heterothermy in cool conditions and extreme heat tolerance at high environmental temperatures. We measured thermoregulatory responses to acute heat stress in three species of caprimulgiforms that nest in areas of extreme heat and aridity, the common poorwill (Phalaenoptilus nuttallii: Caprimulgidae) and lesser nighthawk (Chordeiles acutipennis: Caprimulgidae) in the Sonoran Desert of Arizona, and the Australian owlet-nightjar (Aegotheles cristatus: Aegothelidae) in the mallee woodlands of South Australia. We exposed wild-caught birds to progressively increasing air temperatures (Ta) and measured resting metabolic rates (RMR), evaporative water loss (EWL), body temperature (Tb) and heat tolerance limits (HTL the maximum Ta reached). Comparatively low RMR values were observed in all species (0.35 W, 0.36 W and 0.40 W for the poorwill, nighthawk and owlet-nightjar, respectively), with Tb approximating Ta at 40°C and mild hyperthermia occurring as Ta reached the HTL. Nighthawks and poorwills reached HTLs of 60 and 62°C, respectively, whereas the owlet-nightjar had an HTL of 52°C. RMR increased gradually above minima at Tas of 42, 42 and 35°C, and reached 1.7, 1.9, and 2.0 X minimum resting values at HTLs in the poorwill, nighthawk, and owlet-nightjar, respectively. EWL increased rapidly and linearly as Ta exceeded Tb and resulted in maximum rates of evaporative heat dissipation equivalent to 237-424% of metabolic heat production. Bouts of gular flutter resulted in large transient increases in evaporative heat loss (50-123 %) accompanied by only small increments in RMR (& %). The cavity-nesting/roosting owlet-nightjar had lower HTL and less efficient evaporative cooling compared to the species that nest and/or roost on open desert surfaces. The high efficiency of gular flutter for evaporative cooling, combined with mild hyperthermia, provide the physiological basis for defending Tb well below Ta in extreme heat and is comparable to the efficient cooling observed in arid-zone columbids in which cutaneous EWL is the predominant cooling pathway.
Publisher: The Company of Biologists
Date: 2016
DOI: 10.1242/JEB.138776
Abstract: Birds show phylogenetic variation in the relative importance of respiratory versus cutaneous evaporation, but the consequences for heat tolerance and evaporative cooling capacity remain unclear. We measured evaporative water loss (EWL), resting metabolic rate (RMR) and body temperature (Tb) in four arid-zone columbids from southern African [Namaqua dove (Oena capensis, ∼37 g), laughing dove (Spilopelia senegalensis, ∼89 g) and Cape turtle dove (Streptopelia capicola, ∼148 g)] and Australia [crested pigeon (Ocyphaps lophotes), ∼186 g] at air temperatures (Ta) of up to 62°C. There was no clear relationship between body mass and maximum Ta tolerated during acute heat exposure. Maximum Tb at very highest Ta was 43.1±1.0°C, 43.7±0.8°C, 44.7±0.3°C and 44.3±0.8°C in Namaqua doves, laughing doves, Cape turtle doves and crested pigeons, respectively. In all four species, RMR increased significantly at Ta above thermoneutrality, but the increases were relatively modest with RMR at Ta=56°C, 32%, 60%, 99% and 11% higher, respectively, than at Ta=35°C. At the highest Ta values reached, evaporative heat loss was equivalent to 466%, 227%, 230% and 275% of metabolic heat production. The maximum ratio of evaporative heat loss to metabolic production observed in Namaqua doves, 4.66, exceeds by a substantial margin previous values reported for birds. Our results support the notion that cutaneous evaporation provides a highly efficient mechanism of heat dissipation and an enhanced ability to tolerate extremely high Ta.
Publisher: Informa UK Limited
Date: 03-2014
DOI: 10.1071/MU12098
Publisher: The Company of Biologists
Date: 15-02-2003
DOI: 10.1242/JEB.00147
Abstract: Nectarivorous birds feed on dilute sugar solutions containing trace amounts of amino acids and electrolytes. To meet their high mass-specific energy demands they must often deal with exceptionally high proportionate water fluxes. Despite nectar intake rates that may reach more than five times body mass per day, hummingbirds appear to absorb all ingested water. Here, we report the results of experiments designed to examine the relationship between nectar intake and water turnover in nectar-feeding Palestine sunbirds(Nectarinia osea). Like hummingbirds, sunbirds ingested large amounts of water. At the lowest sucrose concentration (292 mmol l-1), food intake rates reached 2.2 times body mass. Fractional and total water turnover increased linearly with water ingestion, but the fraction of ingested water absorbed by sunbirds decreased from 100% to 36% with increasing water intake rate. Palestine sunbirds may therefore avoid absorbing, and thus having to eliminate, up to 64% of their ingested water load when feeding on dilute nectars. To our knowledge, this is the first documentation of regulation of water flux across the gastrointestinal tract to the body. Our data suggest that sunbirds regulate transepithelial water flux independently of sugar absorption. These intriguing results open the door to many questions about how water transport is regulated in the vertebrate gastrointestinal tract. We suggest that intestinal water and body water form two separate but interacting pools in nectar-feeding birds. Convergence in diet has led to the evolution of many similar traits in hummingbirds and sunbirds. The physiological traits of these two groups that allow the processing of a water and sugar diet, however,may be very different.
Publisher: Frontiers Media SA
Date: 26-08-2021
DOI: 10.3389/FPHYS.2021.708737
Abstract: Establishing proper policies regarding the recognition and prevention of equine heat stress becomes increasingly important, especially in the face of global warming. To assist this, a detailed view of the variability of equine thermoregulation during field exercise and recovery is essential. 13 endurance horses and 12 trotter horses were equipped with continuous monitoring devices [gastrointestinal (GI) pill, heartrate (HR) monitor, and global positioning system] and monitored under cool weather conditions during four endurance rides over a total of 80 km (40 km loops) and intense trotter track-based exercise over 1,540 m. Recordings included GI temperature (T c ), speed, HR and pre- and post-exercise blood values. A temperature time profile curve of T c was constructed, and a net area under the curve was calculated using the trapezoidal method. Metabolic heat production and oxygen cost of transport were also calculated in endurance horses. Maximum T c was compared using an independent s les t -test. Endurance horses (mean speed 14.1 ± 1.7 km h –1 ) reached mean maximum T c (39.0 ± 0.4°C 2 × 40 km in 8 horses) during exercise at 75% of completion of T c exercise and T c returned to baseline within 60 min into recovery. However, the mean T c was still 38.8 ± 0.4°C at a HR of 60 bpm which currently governs “fit to continue” competition decisions. Trotters (40.0 ± 2.9 km h –1 ) reached a comparable mean max T c (38.8 ± 0.5°C 12 horses) always during recovery. In 30% of trotters, T c was still & °C at the end of recovery (40 ± 32 min). The study shows that horses are in iduals and thermoregulation monitoring should reflect this, no matter what type of exercise is performed. Caution is advised when using HR cut-off values to monitor thermal welfare in horses since we have demonstrated how T c can peak quite some time after finishing exercise. These findings have implications for training and management of performance horses to safeguard equine welfare and to maximize performance.
Publisher: University of Chicago Press
Date: 09-2013
DOI: 10.1086/672013
Abstract: Nectar-feeding birds generally demonstrate preference for hexose solutions at low sugar concentrations, switching to sucrose/no preference at higher concentrations. Species vary in the concentration at which the switch from hexose preference occurs this could reflect physiological constraints that would also influence nectar selection when foraging. We recorded concentration-dependent sugar type preferences in three opportunistic/generalist Australian nectarivorous species: Dicaeum hirundinaceum, Zosterops lateralis, and Lichenostomus virescens. All three preferred hexoses up to sugar concentrations of 0.25 mol L(-1) and switched to sucrose/no preference for higher concentrations. Using these and literature records, we investigated physiological mechanisms that may explain the concentration dependence of sugar type preferences and compared diet preference data with foraging records. We measured sucrase activity in Z. lateralis and L. virescens as well as three specialized nectarivorous species (Anthochaera carunculata, Phylidonyris novaehollandiae, and Trichoglossus haematodus) for comparison with published concentration-dependent sugar preference data. Sucrase activity varied between these species ([Formula: see text]). The minimum diet concentration at which birds show no sugar preference was significantly correlated with sucrase activity for the 11 species analyzed ([Formula: see text]). Birds with the lowest sucrase activity showed hexose preference at higher diet concentrations, and birds with the greatest sucrase activity showed either no hexose preference or hexose preference on only the most dilute diets. Foraging data compiled from the literature also support the laboratory analyses for ex le, T. haematodus (preference for hexose over a wide range of diet concentrations, low sucrase activity) also feed primarily on hexose nectars in the wild. Intestinal sucrase activity is likely to contribute to diet selectivity in nectarivorous bird species.
Publisher: Wiley
Date: 22-10-2009
Publisher: The Company of Biologists
Date: 08-2007
DOI: 10.1242/JEB.006114
Abstract: Increasing evidence indicates that small birds have more extensive non-mediated, paracellular intestinal absorption of hydrosoluble compounds than do mammals, although studies have not employed uniform methodologies or demonstrated differences at the tissue level. The mechanistic bases behind apparent species differences are poorly understood. We show using uniform methodology at the whole-animal level that intact, unanesthetized pigeons had significantly higher absorption of l-arabinose and l-rhamnose, two water-soluble compounds used to measure paracellular absorption, than similarly sized laboratory rats. The species differences were also evident using perfused isolated loops of duodenum,showing that the difference in paracellular absorption occurred at the tissue level, even when d-glucose absorption rates(transcellular+paracellular) were similar between the two species. The greater absorption of these probes in pigeons could not be explained by mediated uptake of the putative paracellular probes, or by increased nominal surface area, increased villus area or increased number of tight junctions. Rats and pigeons had comparable absorption of larger probes, which is consistent with similar effective pore size of the tight junction between enterocytes. The elimination of these mechanistic explanations might suggest that pigeon intestine has relatively higher paracellular solvent drag, but pigeon duodenal segments did not have higher net water absorption than rat duodenal segments. Whatever the exact mechanism(s), the paracellular pathway of both species limits substantial (& %) fractional absorption to molecules smaller than about 4.8 Å (Mr ca. 350), and permeability to smaller molecules at the tissue level is higher in pigeons than in rats.
Publisher: Springer Science and Business Media LLC
Date: 14-12-2021
Publisher: The Company of Biologists
Date: 2017
DOI: 10.1242/JEB.155507
Abstract: Evaporative heat loss pathways vary among avian orders, but the extent to which evaporative cooling capacity and heat tolerance varies within orders remains unclear. We quantified the upper limits to thermoregulation under extremely hot conditions in five Australian passerines: yellow-plumed honeyeater (Lichenostomus ornatus ∼17 g), spiny-cheeked honeyeater (Acanthagenys rufogularis ∼42 g), chestnut-crowned babbler (Pomatostomus ruficeps ∼52 g), grey butcherbird (Cracticus torquatus ∼86 g) and apostlebird (Struthidea cinerea ∼118 g). At air temperatures (Ta) exceeding body temperature (Tb), all five species showed increases in Tb to maximum values around 44 – 45 °C, accompanied by rapid increases in resting metabolic rate above clearly defined upper critical limits of thermoneutrality and increases in evaporative water loss (EWL) to levels equivalent to 670 – 860 % of baseline rates at thermoneutral Ta. Maximum cooling capacity, quantified as the fraction of metabolic heat production dissipated evaporatively, ranged from 1.20 to 2.17, consistent with the known range for passerines, and well below the corresponding ranges for columbids and caprimulgids. Heat tolerance limits (HTL, the maximum Ta tolerated) scaled positively with body mass, varying from 48 °C in yellow-plumed honeyeaters to 52 °C in apostlebirds, but were lower than those of three southern African ploceid passerines investigated previously. We argue this difference is functionally linked to a smaller scope for increases in EWL above baseline levels. Our data reiterate the reliance of passerines in general on respiratory evaporative heat loss via panting, but also reveal substantial within-order variation in heat tolerance and evaporative cooling capacity.
Publisher: University of Chicago Press
Date: 03-2012
DOI: 10.1086/664669
Abstract: Two pharmacokinetic methods are used primarily to assess systematic bioavailability of orally dosed water-soluble compounds in vivo, but there have been no direct comparisons of the estimates obtained. The "area under the curve" (AUC) method employs a single oral dose of probe compound(s) followed by multiple blood s ling to obtain plasma concentration time curves. Separate injection of probe(s) followed by multiple blood s ling is used to calculate fractional elimination rate (K(el)) and distribution pool space (S). The "steady state feeding" method relies on ad lib. feeding of a marked diet, with a single blood s le taken to measure steady state feeding concentration of probe(s) K(el) is estimated from the decline in probe concentration in excreta after injection, with a single blood s le taken to estimate S. We compared these methods directly in the Australian red wattlebird (Anthochaera carnunculata), measuring absorption of (3)H-L-glucose. The K(el) values estimated using the steady state feeding protocol were significantly higher, and estimates of S and bioavailability consequently lower, compared with the AUC protocol. The AUC method relies on fewer assumptions and allows simultaneous comparisons of absorption by mediated and nonmediated (i.e., paracellular) mechanisms but cannot be easily applied to freely feeding animals. The steady state feeding method allows work with smaller species and exploration of the effects of feeding on nutrient uptake but requires careful attention to the validity of assumptions that increase error in the calculations.
Publisher: MDPI AG
Date: 10-02-2023
Abstract: Efforts to mitigate the effects of feral cats through the management of remnant or reintroduced populations of threatened species, are often unsuccessful due to predation by control-averse feral cats, or ‘problem in iduals’. In order to target these animals, we have developed the Population Protecting Implant (PPI). PPIs are designed to be implanted subcutaneously in a native animal. If the animal is preyed upon, and the implant ingested by a feral cat, release of a toxic payload is triggered in the acidic stomach environment and the problem in idual is eliminated. We introduce the first toxic implant incorporating the poison sodium fluoroacetate. Manufactured via fluidised-bed spray coating, toxic implants exhibited uniform reverse enteric coatings and low intra-batch variation. Toxic implants were found to exhibit favourable stability at subcutaneous pH in vitro, and rapidly release their toxic payload in vitro at gastric pH. However, limited stability was demonstrated in rats in vivo (~39–230 d), due to the use of a filament scaffold to enable coating and was likely exacerbated by metachromatic interactions caused by 1080. This work highlights that future development of the PPIs should primarily focus on removal of the filament scaffold, to afford implants with increased in vivo stability.
Publisher: Oxford University Press (OUP)
Date: 09-06-2015
DOI: 10.1093/ICB/ICV060
Abstract: Much of what is known about crocodilian nutrition and growth has come from animals propagated in captivity, but captive animals from the families Crocodilidae and Alligatoridae respond differently to similar diets. Since there are few comparative studies of crocodilian digestive physiology to help explain these differences, we investigated young Alligator mississippiensis and Crocodylus porosus in terms of (1) gross and microscopic morphology of the intestine, (2) activity of the membrane-bound digestive enzymes aminopeptidase-N, maltase, and sucrase, and (3) nutrient absorption by carrier-mediated and paracellular pathways. We also measured gut morphology of animals over a larger range of body sizes. The two species showed different allometry of length and mass of the gut, with A. mississippiensis having a steeper increase in intestinal mass with body size, and C. porosus having a steeper increase in intestinal length with body size. Both species showed similar patterns of magnification of the intestinal surface area, with decreasing magnification from the proximal to distal ends of the intestine. Although A. mississippiensis had significantly greater surface-area magnification overall, a compensating significant difference in gut length between species meant that total surface area of the intestine was not significantly different from that of C. porosus. The species differed in enzyme activities, with A. mississippiensis having significantly greater ability to digest carbohydrates relative to protein than did C. porosus. These differences in enzyme activity may help explain the differences in performance between the crocodilian families when on artificial diets. Both A. mississippiensis and C. porosus showed high absorption of 3-O methyl d-glucose (absorbed via both carrier-mediated and paracellular transport), as expected. Both species also showed surprisingly high levels of l-glucose-uptake (absorbed paracellularly), with fractional absorptions as high as those previously seen only in small birds and bats. Analyses of absorption rates suggested a relatively high proportional contribution of paracellular (i.e., non-mediated) uptake to total uptake of nutrients in both species. Because we measured juveniles, and most paracellular studies to date have been on adults, it is unclear whether high paracellular absorption is generally high within crocodilians or whether these high values are specific to juveniles.
Publisher: Wiley
Date: 12-2007
DOI: 10.1002/AJP.20443
Abstract: The common marmoset is one of the few callitrichid species that is not threatened or endangered in the wild, and is widely used in biomedical research, yet relatively little is understood about its digestive physiology. Dietary specialization on plant exudates has lead to relatively reduced small intestines, yet the common marmoset has exceptional dietary breadth, allowing it to successfully utilize a variety of habitats. We predicted that passive, paracellular nutrient absorption would be used by the common marmoset to a greater extent than in other non-flying mammals. We measured the bioavailability and rates of absorption of two metabolically inert carbohydrates not transported by mediated pathways (L-rhamnose and cellobiose, molecular masses of 164 and 342, respectively) to measure paracellular uptake, and of a non-metabolized D-glucose analog (3-O-methyl-D-glucose) to measure total uptake by both mediated and paracellular pathways. We found high bioavailability of 3-O-methyl-D-glucose (83+/-5%), and much higher bioavailability of the paracellular probes than in similarly sized non-flying mammals (30+/-3% and 19+/-2% for L-rhamnose and cellobiose, respectively). Passive, paracellular nutrient absorption accounts for around 30% of total glucose absorption in common marmosets and intestinal permeability is significantly higher than in humans, the only other species of primate measured to date. This may allow the common marmoset to maintain high digestive efficiency when feeding on higher quality foods (fruit, arthropods, gums with higher proportions of simple sugars), in spite of relatively reduced small intestines correlated with adaptations for fermentative digestion of plant gums. We find no evidence to support, in primates, the hypothesis that reliance on paracellular nutrient absorption should increase with body size in mammals, but suggest instead that it may be associated with small body size and/or taxon-specific adaptations to diet.
Publisher: Informa UK Limited
Date: 09-2011
DOI: 10.1071/MU10032
Publisher: Association of Avian Veterinarians (AAV)
Date: 29-03-2020
Publisher: University of Chicago Press
Date: 09-2003
DOI: 10.1086/376917
Publisher: Springer Science and Business Media LLC
Date: 30-12-2022
Publisher: Wiley
Date: 18-12-2018
DOI: 10.1111/DDI.12699
Publisher: Wiley
Date: 11-07-2008
Publisher: Wiley
Date: 10-04-2023
DOI: 10.1002/ZOO.21766
Abstract: Many zoos favor the use of signage to encourage learning and positive visitor experiences as well as discourage negative behaviors by visitors because of its simplicity, relatively low maintenance needed, and low cost. However, current literature suggests that conventional signage has limited impact on visitors in zoos. This study hypothesized that visitors would be less likely to exhibit negative behaviors (e.g., feeding and touching) in the presence of uniformed staff compared to signage. The study was conducted twice a day over 4 weeks with one condition per week (Baseline, Signage, Staff, and Signage + Staff). The total number of visitors and the frequency of negative visitor behaviors were observed. These behaviors reduced from 14.0% (Baseline no signage and no staff) and 13.1% (Signage), to 4.8% (Staff) and 6.1% (Signage + Staff). Both the Staff and Signage + Staff conditions were significantly lower than the Baseline and Signage conditions. However, signage alone did not significantly differ from the baseline condition, when no intervention was implemented, and staff and signage together did not significantly differ from staff alone. This was also observed in both negative visual behaviors and negative tactile behaviors from visitors. The results suggest that methods other than signage may be more effective at reducing undesired visitor behaviors. This study could guide the design of future signage or even potentially encourage zoos to reduce reliance on signs and employ other strategies.
Publisher: Wilson Ornithological Society
Date: 09-2010
DOI: 10.1676/09-179.1
Publisher: Springer Science and Business Media LLC
Date: 13-06-2013
DOI: 10.1038/IJO.2013.110
Abstract: Obesity affects more than half a billion people worldwide, but the underlying causes remain unresolved. It has been proposed that propensity to obesity may be associated with differences between in iduals in metabolic efficiency and in the energy used for homeothermy. It has also been suggested that obese-prone in iduals differ in their responsiveness to circadian rhythms. We investigated both these hypotheses by measuring the core body temperature at regular and frequent intervals over a diurnal cycle, using indigestible temperature loggers in two breeds of canines known to differ in propensity to obesity, but prior to ergence in fatness. Greyhounds (obesity-resistant) and Labradors (obesity-prone) were fed indigestible temperature loggers. Gastrointestinal temperature was recorded at 10-min intervals for the period of transit of the logger. Diet, body condition score, activity level and environment were similar for both groups. Energy digestibility was also measured. The mean core body temperature in obesity-resistant dogs (38.27 °C) was slightly higher (P<0.001) than in obesity-prone dogs (38.18 °C) and the former had a greater variation (P<0.001) in 24h circadian core temperature. There were no differences in diet digestibility. Canines differing in propensity to obesity, but prior to its onset, differed little in mean core temperature, supporting similar findings in already-obese and lean humans. Obese-prone dogs were less variable in daily core temperature fluctuations, suggestive of a degree of circadian decoupling.
Publisher: Wiley
Date: 25-01-2019
Publisher: American Chemical Society (ACS)
Date: 22-08-2022
Publisher: SciELO Agencia Nacional de Investigacion y Desarrollo (ANID)
Date: 09-2000
Publisher: The Company of Biologists
Date: 2018
DOI: 10.1242/JEB.168930
Abstract: Avian orders differ in their thermoregulatory capabilities and tolerance of high environmental temperatures. Evaporative heat loss, and the primary avenue whereby it occurs, differs amongst taxa. Although Australian parrots (Psittaciformes) have been impacted by mass mortality events associated with extreme weather events (heat waves), their thermoregulatory physiology has not been well-characterized. We quantified the upper limits to thermoregulation under extremely hot conditions in two Australian parrots: the mulga parrot (Psephotellus varius ∼55 g) and the galah (Eolophus roseicapilla ∼265 g). At air temperatures (Ta) exceeding body temperature (Tb), both species showed increases in Tb to maximum values around 43–44°C, accompanied by rapid increases in resting metabolic rate above clearly defined upper critical limits of thermoneutrality and increases in evaporative water loss (EWL) to levels equivalent to 700–1000% of baseline rates at thermoneutral Ta. Maximum cooling capacity, quantified as the fraction of metabolic heat production dissipated evaporatively, ranged from 1.71 to 1.79, consistent with the known range for parrots, similar to the corresponding range in passerines, and well below the corresponding ranges for columbids and caprimulgids. Heat tolerance limit (HTL, the maximum Ta tolerated) ranged from 44-55°C, similar to the range reported for passerines, but lower than reported for columbids and caprimulgids. Our data suggest that heat tolerance in parrots is similar to that of passerines. We argue that understanding how thermoregulatory capacity and heat tolerance vary across avian orders is vital for predicting how climate change and the associated increase in frequency of extreme weather events may impact avian populations in the future.
Publisher: The Royal Society
Date: 17-06-2008
Abstract: Small birds and bats face strong selection pressure to digest food rapidly in order to reduce digesta mass carried during flight. One mechanism is rapid absorption of a high proportion of glucose via the paracellular pathway (transfer between epithelial cells, not mediated by transporter proteins). Intestinal paracellular permeability to glucose was assessed for two nectarivorous passerines, the Australian New Holland honeyeater ( Phylidonyris novaehollandiae ) and African white-bellied sunbird ( Cinnyris talatala ) by measuring the bioavailability of radiolabelled, passively absorbed l -glucose. Bioavailability was high in both species and increased with diet sugar concentration (honeyeaters, 37 and 81% and sunbirds, 53 and 71% for 250 and 1000 mmol l −1 sucrose diets, respectively). We conclude that the relative contribution of paracellular to total glucose absorption increases with greater digesta retention time in the intestine, and paracellular absorption may also be modulated by factors such as intestinal lumen osmolality and interaction with mediated glucose uptake. The dynamic state of paracellular absorption should be taken into account in future studies.
Publisher: Public Library of Science (PLoS)
Date: 15-04-2013
Publisher: Wiley
Date: 24-11-2010
Publisher: The Company of Biologists
Date: 09-2004
DOI: 10.1242/JEB.01169
Abstract: Although the renal responses of birds to dehydration have received significant attention, the consequences of ingesting and processing large quantities of water have been less studied. Nectar-feeding birds must often deal with exceptionally high water intake rates in order to meet their high mass-specific energy demands. Birds that ingest large volumes of water may either eliminate excess water in the kidney or regulate the volume of water absorbed in the gastrointestinal tract. Because water absorption in the gastrointestinal tract of Palestine sunbirds (Nectarinia osea)decreases with increasing water ingestion rate, we predicted that glomerular filtration rate (GFR) in these birds would not be unusually high in spite of large ingested water loads. When feeding on dilute sucrose solutions, sunbirds ingested between 4 and 6 times their body mass in nectar per day, yet they were able to compensate for varying nectar energy density and increased thermoregulatory energy demands with no apparent difficulty. GFR was lower than predicted (1976.22±91.95 μl h-1), and was not exceptionally sensitive to water loading. Plasma glucose concentrations were high, and varied 1.8-fold between fasted (16.08± 0.75 mmol l-1) and fed (28.18±0.68 mmol l-1) sunbirds, but because GFR was low, glucose filtered load also remained relatively low. Essentially the entire glucose filtered load (98%) was recovered by the kidney. Renal fractional water reabsorption (FWR) decreased from 0.98 to 0.64 with increasing water intake. The ability of Palestine sunbirds to reduce the absorption of ingested water in the gastrointestinal tract may resolve the potential conflict between filtering a large excess of absorbed water in the kidney and simultaneously retaining filtered metabolites.
Publisher: SAGE Publications
Date: 10-2018
DOI: 10.3184/175815618X15366607700458
Abstract: Desert birds must cope with occasional and unpredictable heat waves, which are slowly becoming more frequent with climate change. Different orders of birds have different physiological and behavioural capacities that may aid survival during a heat wave. To date, the expression of genes related to heat exposure have not been studied across different bird orders. We hypothesised that acutely exposing native Australian birds whose natural habitat include arid environments to a high temperature (45 °C), similar to during a heat wave, would result in the upregulation of genes with protective effects against cell damage (BCL-2, VEGFA and heat shock proteins) and inflammation (interleukins), as well as the downregulation of genes involved in the coagulation pathway (fibrinogen). We used eight each of captive-bred Budgerigars (Melopsittacus undulatus), Zebra Finches (Taeniopygia guttata) and Diamond Doves (Geopelia cuneata). Four birds of each species were exposed to a temperature that was within the zone of thermal neutrality (35 °C), while the other four birds were exposed to a higher temperature (45 °C). The mRNA expression of selected genes were then measured using high-throughput qPCR platform (Fluidigm ® , BioMark ™ ). The results supported the hypothesis that acute exposure to a high temperature would result in the upregulation of heat shock protein (HSP) genes, but there was no significant upregulation of other genes with protective effects against cell damage nor genes associated with inflammation. The results also do not support the hypothesis that acute heat exposure would result in downregulation of the genes involved in the coagulation pathway in these birds. Among all the tissues that were analysed, the gastrointestinal tissue had the highest number of upregulated HSP genes, possibly indicating that this tissue requires the most protection to continue functioning. Diamond Dove organs also had the highest number of HSP genes upregulated, possibly a reflection of their ability to better protect their cells at high temperatures.
Publisher: The Company of Biologists
Date: 2013
DOI: 10.1242/JEB.075176
Abstract: Nectarivores face a constant challenge in terms of water balance, experiencing water loading or dehydration when switching between food plants or between feeding and fasting. To understand how whitebellied sunbirds and New Holland honeyeaters meet the challenges of varying preformed water load, we used the elimination of Intramuscular-injected [14C]-L-glucose and 3H2O to quantify intestinal and renal water handling on diets varying in sugar concentration. Both sunbirds and honeyeaters showed significant modulation of intestinal water absorption, allowing excess water to be shunted through the intestine on dilute diets. Despite reducing their fractional water absorption, both species showed linear increases in water flux and fractional body water turnover as water intake increased (both afternoon and morning), suggesting that the modulation of fractional water absorption was not sufficient to completely offset dietary water loads. In both species, glomerular filtration rate (GFR) was independent of water gain (but was higher for the afternoon), as was renal fractional water reabsorption (measured in the afternoon). During the natural overnight fast, both sunbirds and honeyeaters arrested whole kidney function. Evaporative water loss in sunbirds was variable but correlated with water gain. Both sunbirds and honeyeaters appear to modulate intestinal water absorption as an important component of water regulation to help deal with massive preformed water loads. Shutting down GFR during the overnight fast is another way of saving energy for osmoregulatory function. Birds maintain osmotic balance on diets varying markedly in preformed water load by varying both intestinal water absorption and excretion through the intestine and kidneys.
Publisher: Wiley
Date: 15-05-2017
DOI: 10.1111/COBI.12903
Publisher: Springer Science and Business Media LLC
Date: 08-11-2012
Publisher: University of Chicago Press
Date: 05-2017
DOI: 10.1086/690484
Abstract: Birds need to respond to weather changes quickly and appropriately for their own well-being and survival. The inability to respond appropriately to heat waves can be fatal to in idual birds and can translate into large-scale mortality events. We investigated corticosterone (CORT) and heterophil∶lymphocyte (H∶L) ratio responses of budgerigars (Melopsittacus undulatus), zebra finches (Taeniopygia guttata), and diamond doves (Geopelia cuneata) to heat exposures. The birds were exposed to a temperature similar to what they experience during a typical summer day (35°C) and a higher temperature (45°C) similar to that experienced during a heat wave. There were no significant increases between the CORT concentrations before and after heat exposure in zebra finches and budgerigars at 35° and 45°C, but there was a significant increase in CORT concentrations in diamond doves after exposure to 45°C. The H∶L ratios increased significantly after heat exposure in budgerigars at 35° and 45°C and in diamond doves at 35°C. No significant correlation was found between the changes in CORT and H∶L ratios. The data suggest that there are species differences in birds' stress responses to heat exposure that may reflect their ability to detect and adapt to high temperatures. There appear to be differences between the two types of stress measurements, which may reflect differences in the timescales of these responses.
Publisher: Informa UK Limited
Date: 17-12-2019
DOI: 10.1080/03079457.2018.1546824
Abstract: The pathophysiology of heat illnesses in birds has not been well characterized. In this study, we describe the changes in heart rate, respiratory rate, blood biochemistry and histopathological findings in galahs and rock doves after heat exposure under standardized conditions designed to induce heatstroke. Birds in the heat-exposed group were exposed to environmental heat stress and compared to control birds. Both groups of birds were under general anaesthesia throughout the experiment and serial blood collections were performed for biochemical analyses, while organs were collected at the end of the experiment for histopathology. No electromyography traces consistent with the onset of heat cr s were observed in any of the birds. Biochemical changes suggestive of skeletal muscle and hepatocellular injury, including hyperkalaemia and increased serum muscle and hepatic enzyme activities, were often observed in heat-exposed galahs and rock doves at the onset of heatstroke. Microscopic analyses did not reveal any significant cardiac changes, although some lungs had signs of acute congestion. Some heat-exposed rock doves had microscopic changes indicative of necrosis in the pectoral muscle. There were significant hepatic changes in some heat-exposed galahs, but not in rock doves. This suggests that there may be species differences amongst birds in the organs most affected by heatstroke. The observed species differences in the physiological, biochemical and histopathological changes indicate that bird species should be studied separately for clinical syndromes such as heatstroke. RESEARCH HIGHLIGHTS Biochemical changes suggestive of skeletal muscle and hepatocellular injury in heat-exposed galahs and rock doves at the onset of heatstroke No electromyography traces consistent with the onset of heat cr s were observed Some heat-exposed rock doves had indications of necrosis in the pectoral muscle There were significant hepatic changes in some heat-exposed galahs.
Start Date: 2006
End Date: 12-2008
Amount: $290,000.00
Funder: Australian Research Council
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