In oreler to evaluate the amount of the diameter's variations and its relation with resistance of the fibers, samples of Corriedale sheep wool, maintained in natural pastures. from Isla Tierra del Fuego, MagaIIanes, were studied.
Measurements of the diameter of fibers were made in the middle portian of the fiber. corresponding to the summer, faII, winter and spring grows. The samples were taken in SpringhilI, Onaisín and Porvenir, three places with different ecological conditions and with natural pastures. A notable seasonal variation is observed in the diameter of fibers. The smaIIest diameter of fiber of the fIock, were obtained in winter and the largest in summer. In the case of ram-hoggets and ewe-hoggets and rams, the largest diameters were noted in spring-summer and the smallest tiber diameter in falI-winter. This variation in fiber diameter is attributed to 1) seasonal changes in the feed value of the natural pasture, 2) the increased nutritional requirements of the 10w winter temperatures, and 3) the pregnancy in the ewes. The seasonal variation of fiber diameter, ranged from a minimum of 19.29% (34.61 to 27.94 μ) to a maximum of 42.80% (28.41 to 16,33 μ ) in ewe-hoggets and rams, respectively. The obsened variation represents a decrease in the resistance which varies between 19.65 and 51.10%. Other posibilities in obtaining a wool production with minimum defects are discussed.