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

Alexiev, I.; Gudev, D.; Ralcheva, S.; Moneva, P.; Zunev, P.

Bulgarian Journal of Agricultural Science 10(6): 745-751


ISSN/ISBN: 1310-0351
Accession: 012934022

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Five six-month-old male (Anglo Nubian x Bulgarian white-grading) kids were used in the present experiment. The kids were either exposed to the sun or kept in shade during warmer summer days when the ambient temperature was over 30 degrees 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 07.00 to 21.00 h 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, SB and canvas shade, respectively. The rectal temperature of the kids exposed to direct solar radiation peaked at 13.00 h whereas the highest RT value in the SB kids was observed at 21.00 h. 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 played a certain role in the control of RR at 21.00 h in SB kids. Anglo Nubian (AN) kids exposed to sun showed 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 AN kids exposed to the sun were transferred into canvas shade for 30 min, they demonstrated lower magnitude of RR compared to those of the other two breeds. The heart rate was increased insignificantly during the day and peaked at 21.00 h both in kids kept under the sun or in shade. Taken as a whole, our results showed that AN kids exceeded Bulgarian white and Toggenburg kids in their ability to tolerate higher ambient temperature.