Abstract
High climatic temperature is the most important factor hampering livestock productivity in tropical and arid regions. Therefore, the current study aimed to investigate the interaction between coat color and heat tolerance in two principal Saudi sheep breeds; Najdi (black colored coat) and Naemi (white colored coat). Najdi and Naemi adult sheep of different age groups and both sexes, raised under direct solar radiation in different parts of the Riyadh region were used. The thermo-physiological measurements were taken from sheep flocks raised under a similar production system in different parts of Riyadh region during the summer season. The recorded rectal temperature (Tre) was significantly (P < 0.05) higher in the white coat colored breed compared to the black coat colored breed. Consequently, the calculated heat tolerance coefficient (HTC) was significantly (P 0.05) higher in the black coat colored breed compared to the white coat colored one. No significant (P 0.05) differences were observed concerning skin temperature (Tsk), packed cell volume (PCV) and plasma albumin levels between the two breeds. The obtained results indicate that white coat color of sheep grazing under a hot arid climate is not a crucial trait of heat tolerance and adaptation. Other hair coat characteristics and evaporative cooling traits might play important role in the adaptation of the black coat colored sheep breed grazing under hot arid conditions.