Docking and Cropping

Docking

Traditionally docking tails originated in the Roman empire where worms in the tail of the dog were thought to cause rabies. This belief led to the tradition of cutting off the tail as a preventive measure. More recently hunting dogs had tails docked to prevent them from becoming tangled in undergrowth. Some hunting and fighting dogs ears were cropped and tails were docked to make them less available as targets for other animals that they might fight with.
Docking is usually performed within a few days after birth to ensure that the wound heals properly, it is thought that newly born puppies hardly feel the surgery. Reputable breeders have docking performed by a licensed vet. Today, many countries consider docking to be cruel or mutilation and ban it entirely.

From 6 April 2007 in England, and 28 March 2007 in Wales, the docking of dogs tails has been banned except for certain working dogs or where the procedure is required for the purposes of medical treatment. The docking of dogs tails has been banned in Scotland, without any exception for working dogs, under the Animal Health and Welfare (Scotland) Act 2006 with effect from 30 April 2007. There has been no change in the law in Northern Ireland.

Full details are on the Royal College of Veterinary Surgeons website here.

Cropping

Cropping is the surgical removal of part of the ear. After surgery the ear stands up rather than lying in its natural hanging position. Cropping ears is illegal in the UK but is widely practiced in the USA.
Cropping is often performed on breeds used for guarding as the dog appears more ferocious with cropped ears than it does with naturally hanging ears.