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The effect of ingested NACL on body temperature in two avian species : the domestic fowl and the glaucous-winged gull

University of British Columbia

The relative effects of ingested sodium chloride (NaCl) on body temperature were examined in two avian species; the domestic fowl (Gallus domesticus), a terrestrial bird which excretes NaCl renally, and the Glaucous-winged gull (Larus qlaucescens), a marine bird which excretes NaCl both renally and extrarenally. Plasma sodium ([Na⁺]pl), potassium ([K⁺]pl), chloride ([Cl⁻]pl, ionized ([Ca²⁺]pl) and total calcium ([Ca]pl) concentrations, plasma osmolality (Osmolpl), body temperature, evaporative water loss (EWL), total body water (TBW), respiratory frequency (f), minute ventilation (VE) , and panting thresholds were determined in roosters and gulls exposed to increasing dietary NaCl levels. High dietary NaCl significantly raised gull resting body temperature (40.4°C ± 0 . 4°C) to 41. 0°C ± 0 .5°C (P<0.05) but did not alter rooster body temperature (41.0°C ± 0.2°C) significantly. [Na⁺]pl increased by 5.4% (P<0.01) in gulls and by 3.7% (P<0.01) in roosters, and was correlated with body temperature in gulls (r = 0.497, n = 25) . . [Ca²⁺]pl increased (roosters, 5.5%, P<0.01; gulls, 11.8%, P<0.01) when [Na⁺]pl was high. Plasma sodium to calcium ratios were not altered and were unrelated to body temperature in both species. High dietary NaCl elevated the internal threshold for panting in roosters from 41.95 ± 0.41°C to 42.35 ±0.3 6°C (P<0.05), and the increase was associated with an increase in Osmolpl (303.6 ± 4.0 mosmol/kg to 319.5 ± 4.3 mosmol/kg, P<0.01). In gulls Osmolpl did not increase, neither did panting threshold. Under thermal stress, body temperature rose more rapidly in both roosters and gulls on high salt diets. VE, f, and weight-specific EWL at 30°C, were unaffected in both species by high salt intake. TBW was not related to resting body temperature and did not change significantly with high NaCl intake in either species. It is concluded that resting body temperature is elevated by increased [Na⁺]pl in concentration-dependent fashion rather than a raised Na : Ca ratio in birds with and without salt glands. [Ca²⁺]pl is elevated when [Na⁺]pl is high. The additional Ca²⁺ probably originate from a source other than the bound fraction in plasma; possibly from the intracellular Ca²⁺ pool. The ability of a bird to maintain a stable panting threshold is related to its ability to maintain a stable Osmolpl. EWL, VE, and f are unaffected by NaCl intake unless severe heat stress is imposed.

Text

2010-11-16

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http://hdl.handle.net/2429/29979

Zoology

University of British Columbia

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