Lambs' tails may be docked for cleanliness and to minimize fly strike, but cosmetic, excessively short tail docking can lead to an increased incidence of rectal prolapse and is unacceptable for the welfare of the lamb. We recommend that lambs' tails be docked at the level of the distal end of the caudal tail fold and at the earliest age practicable. Because tail docking causes pain and discomfort, the AVMA recommends the use of procedures and practices that reduce or eliminate these effects, including the use of approved or AMDUCA-permissible clinically effective medications whenever possible.
Welfare Implications of Tail Docking of Lambs (PDF)
Docking of Lambs' Tails Video
2015 American Veterinary Medical Association