The growing period is called anagen and the resting period is called telogen. Small secondary hairs of goats are nonmedullated. Guard hairs are undesirable in wool-bearing breeds, because the medulla makes the hair brittle and this hair type does not take up dye well. Hair fibers are somewhere in between wool and Kemp fibers in their morphologic characteristics. Kemp fibers are coarse, relatively short, and poorly crimped. True wool fibers are fine and tightly crimped. In Angora goats and sheep, three types of wool are recognized: true wool, Kemp fibers, and hair fibers. Secondary hairs make up a greater proportion of the hair coat compared with primary or guard hairs in goats and sheep. Likewise, failure to complete shearing by the time hot weather arrives may predispose the animals to heat exhaustion. Thus shearing sheep when environmental temperatures are still low is not without risk. A short, thick hair coat is best for regulating body temperature during high environmental temperatures, whereas long, fine hair coats are most efficient at low environmental temperatures. 1 Hair is important for thermoregulation. 1, 2 Both sheep and goats have relatively thin skin, with an average thickness of 2.6 mm in sheep and 2.9 mm in goats. It also aids in thermoregulation, acts as a sensory organ, and communicates through the secretion of chemicals. The skin functions as a protective barrier to the environment. This section reviews the unique anatomy and relevant physiology that is pertinent to veterinary management of small ruminant diseases and conditions. A complete discussion of the anatomy and physiology of the skin is beyond the scope of this chapter.
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