Some Aspects of Thermo-Regulation in Water Deprived Camels Under the Semi-Arid Conditions of the North-Western Coastal Desert in Egypt

Abstract

This study was conducted at Maryout Experimental Station near Alexandria, 32° latitude affiliated to the Desert Research Center in Cairo. In this study, the effect of heat stress resulting from the combined effect of water deprivation, the housing environment and season of the year on the changes of rectal (RT) and skin temperature (ST) and their amplitude (differences between morning and afternoon values), as well as gradients between core and surface temperatures and the ambient temperature were investigated in eight non-pregnant and non lactating female dromedary camels fed at the maintenance level. Half the animals were watered daily whereas the other half was intermittently watered, once every 7 days. Moreover, half the animals were kept outdoors and not sheltered whereas the other half was housed indoors. The experimental treatments were repeated three times between April and August to represent spring, early summer and late summer seasons. Climatic (ambient temperature (Ta), relative humidity (RH%) and temperature humidity index (THI) and animal data (RT and ST) were recorded twice daily at 7:00 am and 2:00 pm for seven consecutive days representing a complete water deprivation cycle.It was evident that the housing environment in the morning was a significant source of variation affecting both RT and ST and their amplitude, as well as core, skin and ambient temperature gradients. Water deprivation also represented another significant source of variation that affected (RT), both in the morning and in the afternoon. However, (ST) was significantly affected by season only in the morning. All the above parameters were significantly affected by days of the water deprivation cycle.It was noticeable that the RT of the water deprived camels kept outdoors was consistently lower than their control mates. Largest average RT amplitude was observed in the water deprived camels housed outdoors which was 4 folds of their water deprived mates housed indoors. On the other hand, ST behaved differently in such a way that in the water deprived camels it was frequently higher than in the daily watered controls. Evident was the capacity of camels to maintain constant, the overall rectal-air temperature gradient through varying rectal-skin and skin-air gradients, and invariably in opposite direction. This was aided by the fact that (Ta) were constantly lower than the (RT) and (ST). Hence, the temperature of the skin and its regulation determines to a large extent the core temperature of camels.