Effect of altered ambient temperature on breathing in ponies

Abstract

The objective was to determine the effect of moderate changes in ambient temperature (TA) on breathing and body temperature in ponies chronically exposed to a TA of 21 degrees C in the summer and 5 degrees C in the winter. Normal (n = 6) and chronic carotid body-denervated (n = 6, 1-2 yr) ponies were studied during 1) winter months over 3-4 days at 5 (control TA) and 23 degrees C and 2) summer months over 2-4 days at 21 (control TA), 30, and 12 degrees C. Neither rectal nor arterial temperature changed with any alteration of TA (P greater than 0.10). Skin temperature (Tsk) always changed by 2-4 degrees C in the same direction as changes in TA (P less than 0.01), and Tsk was the only variable that differed between summer and winter control TA. While breathing room air 24-48 h after TA was altered, pulmonary ventilation (VE) and breathing frequency (f) were approximately 100 and 300%, respectively, above control with elevated TA and approximately 25-50% below control with reduced TA (P less than 0.01). Changes in f were closely related to changes in Tsk. Tidal volume (VT) changed inversely with changes in TA. Generally, while breathing room air, arterial PCO2 (Paco2) did not change from control during the first 48 h of altered TA. In studies when inspired CO2 was elevated VT increased by the same amount at all TA; f increased at low and control TA but decreased at elevated TA; and VE and Paco2 both increased relatively less at elevated TA, but the VE-Paco2 slope was independent of TA.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of locomotor‐respiratory coupling on the pattern of breathing in horses.

“…Finally, it should be noted that the relative tachypnoea inherent in the exercise patterns of both ponies (Kaminski, Forster, Bisgard, Pan & Dorsey, 1985) and dogs (Saibene et al 1981) VT / VT,rest Miyamoto, 1989) and rabbits (Corio, Palisses & Viala, 1993) which indicate a graded strength of LRC in function of velocity, gait and activation of spinal locomotor generators. This study shows that the pattern of breathing is subject to different types of regulation during exercise and chemical stimulation at rest, mainly because of a substantial interaction of locomotor and respiratory rhythm.…”

Welfare issues related to transport and handling of both trained and unhandled horses and ponies

“…Avoiding heat and cold stress in transit is largely a matter of common sense, although for journeys longer than 8 h in the EU, legislation (Council Regulation (EC) 1/2005) specifies air temperatures should be within the range 5–30°C (±5°C). Thermal stress was observed in ponies exposed to ambient temperatures above 30°C, whereas 21°C was considered thermoneutral (Kaminski et al . 1985).…”

“…Avoiding heat and cold stress in transit is largely a matter of common sense, although for journeys longer than 8 h in the EU, legislation (Council Regulation (EC) 1/2005) specifies air temperatures should be within the range 5-30°C (Ϯ5°C). Thermal stress was observed in ponies exposed to ambient temperatures above 30°C, whereas 21°C was considered thermoneutral (Kaminski et al 1985). During hot, sunny weather, transport should take place overnight rather than in the middle of the day and vehicles should not be stationary in sunshine, especially if unroofed, but rather should be parked in the shade or kept moving.…”

Comparative Control of Respiration

“…Species that do not pant, but rely more on sweating than respiratory evaporative heat loss (such as man or horse), still exhibit an increased ventilation in excess of that attributable to the increased metabolic rate that may be associated with an increased body temperature (Robinson, 1949;Kaminski et al, 1985). In humans the increase in frequency is attributable to equivalent decrements in inspiratory and expiratory times (Petersen and Vejby-Christensen, 1977).…”

“…Regardless, some degree of "true" hyperventilation may exist in mammals due to the development of hypocapnia during heat exposure (Calder and SchmidteNielsen, 1966;Jennings, 1984). Kaminski et al (1985) noted that, even with no change in deep body temperature, there is still a close relationship between changes in ambient temperature and changes in skin temperature in ponies, and changes in respiratory frequency are closely related to changes in skin temperature. They pointed out that it is not the absolute value of the ambient temperature that is important in this response, but the change from the acclimatization temperature.…”