The effects of dock length on the incidence of rectal prolapse in lambs
A study was conducted at the Texas Tech University Sheep Center during the spring of 2004 and 2005. The purpose of the study was to investigate the effects of tail docking length, as well as other major contributing factors, on the incidence of rectal prolapses in lambs. The study was prompted because of the controversy associated with rules and regulations concerning dock length at local, county, state, and national livestock shows. There was a total of 382 (212 in 2004 and 170 in 2005) lambs in the study all of which were conceived and born at the Texas Tech University Sheep Center. Lambs received one of three docking treatments: 1) short-tail was removed as close to the body as possible; 2) medium-tail was removed at a location midway between the attachment of the tail to the body and the attachment of the caudal folds to the tail; and 3) long-tail was removed at the attachment of the caudal folds to the tail. An effort was made to evenly distribute treatments among breeds, gender, and birth types. The lambs were fed a high-concentrate diet in a feedlot environment. The overall incidence of rectal prolapse was 2.1%. Statistical significance was not observed among the three docking treatments; however twice as many lambs with a medium docking treatment experienced a rectal prolapse compared to long- or short-docked lambs. Female lambs had a greater (P < 0.05) incidence of rectal prolapse than male lambs. Additionally, the hair sheep in the study experienced 87% of the rectal prolapses observed. Sire differences were evaluated, and one sire was responsible for 62.5% of the prolapses in the study. The high percentage of hair sheep lambs prolapsing in the study suggests that genetics may be a contributing factor to predisposing lambs to rectal prolapse. Although the results of the study did not find statistical significance as had previous studies concerning dock length and the incidence of rectal prolapse, it does not eliminate dock length as a potential contributing factor to rectal prolapse in lambs. The results of this study suggest that there are equal to or more significant than tail dock length that rectal prolapse in lambs. More research needs to be conducted with reference to the given issue before additional rules and regulations are implemented at livestock shows.