Sheep were originally self-shedding so kept enough wool to protect themselves from temperature extremes. The fleece provides effective insulation against both cold and heat. Due to breeding and genetic manipulation, however, sheep raised by the wool industry produce excessive amounts of wool so now have to be shorn. Shearers are usually paid by volume, not by the hour, which encourages fast work without regard for the welfare of the sheep. This often results in horrendous injuries to the sheep with open wounds being sewn up without anaesthetic. Sheep are known to be beaten into submission should they not stay still and drug use has been proven to be prevalent in the shearing industry. Despite the fact that shearing causes sheep a high degree of stress, they are usually shorn twice a year with one of those times being late autumn – a time when they are leading into the time of year when they are most in need of their fleece to protect them from the cold. This is to enable farmers to make a greater amount of profit from their wool.