Review: Water stress in sheep raised under arid conditions

Abstract

Sheep breeds which are indigenous to arid and semi-arid regions are known for their ability to adapt to rustic environments, to climatic variations as well as to shortages in resources. Water scarcity, often combined with heat stress, is a common challenge facing these animals, causing physiological perturbations and affecting the animal's productivity. This review reports the effect of different forms of water stress on physiological indicators, blood parameters, thermoregulation and immunological status in sheep. Although the breed effect may be significant, the following are generally observed common responses: drop in feed intake and weight loss, increase in evaporative cooling through panting, production of a small volume of highly concentrated urine, haemoconcentration, high blood osmolality, and immunosuppression. Prolonged water shortage may affect lamb birth weight and survival, and lead to a decrease in milk production, especially in non-adapted breeds, which could lead to important economic losses, as reported in heat-stressed sheep husbandries. Novel stress alleviation approaches are also presented, such as vitamin C supplementation.