I. ALEXIEV1, D. GUDEV1, S. RALCHEVA1, P. MONEVA1 and P. ZUNEV2
1 Institute of Animal Science, BG-2230 Kostinbrod, Bulgaria
2 Institute of Mountainous Animal Breeding and Agriculture, BG-5600 Troyan, Bulgaria
ALEXIEV, I., D. GUDEV, S. RALCHEVA, P. MONEVA and P. ZUNEV, 2004. Thermoregulation in kids. II. Diurnal dynamics of rectal temperature, respiration rate and heart rate in Toggenburg kids kept in sun or in shade. Bulg. J. Agric. Sci., 10: 617-622
Five, 6-month old kids (Toggenburg x Bulgarian white-grading) were used to study the effect of high ambient temperature on the dynamics of rectal temperature (RT), respiration rate (RR) and heart rate (HR) in kids kept in sun or in shade. The kids in shade were housed either in solid barn with half opened front side (SB) or kept in canvas shade. All measurement were carried out when ambient temperature was more than 30°C.
The physiological parameters were registered from 7 a.m. to 9 p.m. at 120-min intervals. The meteorological parameters were controlled at the same intervals immediately before the measurement of the physiological parameters. The heat load, as indicated by RT and RR, was higher in the exposed to sun kids. The highest value of RT in SB kids (at 9 p.m.) was accompanied with lower magnitude of RR in comparison with the RR in the exposed to sun kids having the same rectal temperature (around 10 a.m.). It is suggested that diurnal rhythm of pineal activity play a role in the control of RR during the late afternoon hours. Rectal temperature and RR in Toggenburg kids, exposed to sun were higher than those in Bulgarian white kids. It is suggested that both the rate of the temperature rise and the closeness of rectal temperature value to the critical temperature threshold control the magnitude of RR. Rectal temperature and RR of the exposed to sun kids fell abruptly 30 min after their placement into a canvas shade by 12 a.m. Heart rate showed a steady increase (P>0.01) during the day and peaked at 9 p.m. both in kids kept in sun or in shade.