EFFECTS OF SEASON, HOUSING ENVIRONMENT AND WATER DEPRIVATION ON RECTAL AND SKIN TEMPERATURE REGULATION IN BARKI DESERT SHEEP

Abstract

This study was conducted at Maryout Experiment Station near Alexandria, 32° latitude, affiliated to the DesertResearchCenter in Cairo. In this study, the effect of heat stress resulting from the combined effects 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 adult 4-5 years old Barki ewes fed at the maintenance energy level. Half the animals were watered daily whereas the other half was watered intermittently, once every 3 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. Ambient temperature (Ta), relative humidity (RH%) and animal data, rectal (RT) and skin (ST) temperatures were recorded twice daily at 7:00 AM and 2:00 PM for three consecutive days representing a complete water deprivation cycle. It was noticeable that the housing environment was a significant source of variation affecting RT, ST and their amplitude, as well as core, skin, and ambient temperature gradients. RT and ST were always lower outdoors than indoors in the morning. Conversely, in the afternoon they were higher outdoors than indoors. Therefore, outdoor RT and ST differences (PM-AM) and gradients were greater than those indoors. On the other hand, time of the year (spring, early summer, and late summer) was a statistically significant source of variation affecting ST and rectal-skin gradient in the afternoon and rectal-air and skin-air in the morning and in the afternoon. The effect of water deprivation was not significant on RT, ST, their amplitude or gradients. Evident was the capacity of sheep 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 sheep. In further studies gradual and long term adaptation experiments, longer cycles of water deprivation and measurement of body fluid changes and stress telated hormones would be needed.