I. ALEXIEV1, D. GUDEV1, S. RALCHEVA1, P. MONEVA1 and P. ZUNEV2
1Institute of Animal Science, BG - 2230 Kostinbrod, Bulgaria
2Institute 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. III. Diurnal dynamics of rectal temperature, respiration rate and heart rate in Anglo Nubian kids, exposed to sun or kept in shade. Bulg. J. Agric. Sci., 10: 745-751
Five six month old, male (Anglo Nubian x Bulgarian white - grading) kids were used in the present experiment. The kids were either exposed to sun or kept in shade during warmer summer days when the ambient temperature was over 30 °C. The kids in shade were housed either in solid barn with half opened front side (SB) or kept in the shade of a canvas. The experiment was undertaken to investigate the effect of heat stress endured by the kids during warmer summer days on the dynamics of rectal temperature (RT), respiratory rate (RR) and heart rate (HR). 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 calculated indices of heat load were 7.69; 3.17 and 2.64 for the kids kept in sun, in SB and in canvas shade respectively. Rectal temperature of the exposed to direct solar radiation kids peaked at 1 p.m. whereas the highest RT value in the SB kids was observed at 9 p.m. However the enhanced RT in SB kids was not accompanied with a significant elevation of RR. It is suggested that in addition to thermal stimuli melatonin stimuli also play a certain role in the control of RR at 9 p.m. in SB kids. Anglo Nubian kids (AN) exposed to sun had around 60% less RR in comparison with those of Bulgarian white and Toggenburg kids. The calculated index of heat load was lowest in AN kids. When the exposed to sun AN kids were transferred into canvas shade for 30 min. they demonstrated once again lower magnitude of RR compared to those of the other two breeds. Heart rate increased insignificantly during the day and peaked at 9 p.m. both in kids kept in sun or in shade. Taken as a whole our results showed that AN kids excel Bulgarian white and Toggenburg kids in their ability to tolerate higher ambient temperature.