Effects of dehydration on thermoregulation in cats exposed to high ambient temperatures

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Abstract
Measurements of evaporative water loss (EWL), metabolic rate (MR), body core temperature (Tc) and respiratory rate (RR) were made in 9 hydrated cats exposed to several high ambient temperatures. Measurements were made in animals hydrated ad lib and during progressive dehydration. At 43 and 40.degree. C, no significant change in EWL occurred during dehydration. At 38 and 35.degree. C, EWL in animals dehydrated for 4 days was reduced to .apprx. 50% of hydrated levels. Reductions in RR correlated highly with reduced EWL, suggesting that control of evaporation in dehydrated cats depended largely on control of RR. Significant elevations in Tc occurred in dehydrated animals at 43, 40 and 38.degree. C and an insignificant upward trend was observed at 35.degree. C. Multiple linear regression analysis of data for EWL, Tc and level of dehydration indicated that dehydration reduced the evaporative response to elevations in Tc and suggested that a change in the sensitivity of the thermoregulatory system occurred. A similar analysis for MR, Tc and level of dehydration showed that dehydration lowered MR at a given Tc. Changes in MR corrected for body temperature during dehydration were principally related to altered ventilatory energy expenditure. A model was formed for estimating the metabolic cost of ventilation in the cat.

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