Sheep need to be sheared because it keeps them cool in the warmer months and reduces the risk of parasitic infestation and disease. If one year’s wool is not removed by shearing, the next year’s growth just adds to it, resulting in sheep that overheat in summer. They have greatly decreased mobility and are in much greater danger from fly-strike, all of which causes suffering and possible death. In other words, they don’t need to wear sweaters!
Wulff & Morgenthaler