A study was conducted at Texas Tech University in 2004 and 2005 to evaluate the possible causes for rectal prolapse in lambs. One particular factor of interest is tail-docking length, so this factor was varied as an experimental treatment. Docking treatments were balanced across breeds, sex, type of birth, and callipyge genotype. The same person docked all of the lambs in the study (n=382).
A short-docked lamb was a lamb for which the elastrator band was placed as close as possible to the lamb's body. A medium-docked lamb was achieved by placing the elastrator band on the tail at a location midway between the attachment of the tail to the body and the attachment of the caudal folds to the tail. To create a long-docked lamb, the elastrator band was placed at the attachment of the caudal folds to the tail. According to the American Sheep Industry Association, American Association of Small Ruminant Practitioners, and various other organizations, the latter is the proper location for docking lambs.
The lambs were creep fed, then fed a high concentrate diet in a feed lot environment until they reached a target weight of 125 lbs. The breeds included in the study were hair sheep (St. Croix and Barbado), Rambouillet, Suffolk x Hampshire, and various crossbreds. 125 lambs either carried or expressed the callipyge gene.
The overall incidence of rectal prolapse was 2.1 percent: 8 out of the 382 lambs. Female lambs (n=6) had a greater incidence of rectal prolapses than wether lambs (n=2). Hair sheep (n=7) accounted for the majority of the prolapses. Five of the lambs that prolapsed had the same sire. Only one callipyge lamb prolapsed.
Results of this study showed NO statistically differences among the three tail docking treatments. These results differ with a recent multi-state study which implicated short tail docks as a cause of rectal prolapses in lambs finished on high concentrate diets. This researcher states "the results of this study do not eliminate dock length as a contributing factor to rectal prolapse, but rather offer other factors that are equally or more significant."
Texas Tech Study [M.S. Thesis]
Multi-state Study [Journal article]
Where to dock lambs