Thermoregulation in Fat-Tailed Awassi, a Desert Sheep, and in German Mutton Merino, a Mesic Sheep

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Abstract
Rectal temperature, metabolic rate and total evaporative water loss were measured and thermal conductance was calculated in five desert fat-tailed Awassi and in five mesic German Mutton Merino (GMM) ewe lambs. Measurements were made under laboratory conditions between 20 and 40 C and at a relative humidity of 30%. Both breeds remained thermostable. The mean daily basal metabolic rate of the Awassi was 57.4 , which is 18% below the predicted, and of the GMM was 60.2 , which is 14% below the predicted. None of the Awassi sheep increased their metabolic rate above the basal level at of 40 C; two of the GMM did and panted vigorously. Both breeds increased their total evaporative water loss as the increased; the GMM at a faster rate. Thermal conductance was similar in the two breeds between 20 and 30 C . At 35 C there was a sharp increase in conductance in the Awassi, whereas conductance in the GMM remained stable. It appears that the Awassi lost more heat than the GMM through means other than the evaporation of water, whereas the GMM used more evaporative water. It may be concluded that both breeds responded similarly to moderate ; however the Awassi showed better ability to withstand high .