Responses to Dehydration in Native Fat-Tailed Awassi and Imported German Mutton Merino Sheep

Abstract

Responses to dehydration were measured in three native fat-tailed Awassi sheep, a breed well adapted to arid and semiarid regions, and in three imported German Mutton Merino (GMM) sheep, a breed that evolved in a temperate climate. Measurements were taken outdoors during the summer in a semiarid area. The sheep were offered water ad libitum, 4.5, 3.0, 2.5, 2.0, and 1.0 liter of water—each water level for 9-12 days. They were also offered 1.8 kg of a balanced concentrated diet and 0.2 kg straw. During this period in which the water allotted was gradually reduced, the Awassi lost 21.0% body weight, 25.8% tritiated water (TOH) space, 15.6% sodium thiocyanate space, and 15.7% T-1824 space while the GMM lost 27.5%, 35.4%, 20.3%, and 25.4% for these same measurements. Except for the sodium thiocyanate space, all losses were significantly higher in the GMM. TOH space reduction amounted to 88.0% of the body weight loss in the Awassi and 90.6% in the GMM. Both breeds reduced their fecal water content from 65% when offered water ad libitum to 45% when offered 1.0 liters of water. The Awassi were able to concentrate their urine to 3,230 mOsm/liter H₂O and the GMM to 2,896 mOsm/liter H₂O (P < .01). Both breeds had an elevated body temperature when dehydrated and remained thermostable. Also both breeds decreased their panting rate with a reduction in water intake. Following the dehydration period, in one drinking the Awassi were able to consume water amounting to 97% of their TOH space loss, whereas the GMM consumed water amounting to 64% of their TOH space loss. It was concluded that the GMM can cope with water shortage almost as well as the Awassi and that both breeds are suitable to semiarid areas. However, the Awassi can maintain its body weight and body fluids to a greater degree during dehydration and is able to replace its loss of body fluids more quickly.