Measuring Sheep Tails: A Preliminary Study Using Length (Mm), Vulva Cover Assessment, and Number of Tail Joints

SIMPLE SUMMARY: It is common for sheep to have tails docked as lambs, predominantly to reduce flystrike. It is recommended that tails are docked long enough to cover the vulva in ewes and at a similar length in males. There are many ways that tail length in sheep is described and measured, but there is a lack of congruency across the different description and measurement methods. This study aimed to investigate the reliability of three common ways to measure and describe docked sheep tail length, using 99 Merino ewes, 51 yearlings (1.4-year-olds) and 48 weaners (5-month-olds). Length and vulva cover assessment were the methods with the most reliable results, joint palpation was the least reliable method of tail measurement. The tails in this sample that were of the recommended length, covering the vulva, measured 10.8–16.2 mm longer than tails not covering the vulva, at 63.7 mm for weaners and 57.6 mm for yearlings on average, and contained more than two coccygeal vertebrae. This research presents two reliable methods of sheep tail measurement for two age groups and provides a foundation for future research into method refinement and tail length monitoring. ABSTRACT: Docking sheep tails is a long-standing practice that, when done at the recommended length, reduces the risk of flystrike. The recommended length is to cover the vulva of ewes and to a similar length in males. This length is often equated to three coccygeal joints left intact, and there are many other ways the recommended length is described by researchers, industry, and government. This study compared the observer consistency and retest consistency using three different tail length measurement methods: vulva cover assessment, length (mm), and joint palpation. The tails of 51 yearling and 48 weaner Merino ewes were assessed by two observers. Length and vulva cover assessment methods provided the most reliable results, and joint palpation was the least reliable method of tail measurement. In the sample, tails that covered the vulva of yearlings and weaners measured 57.6 mm (n = 14) and 63.7 mm (n = 30) on average, respectively, and contained two coccygeal joints (more than two coccygeal vertebrae). Tails that did not cover the vulva of yearlings and weaners measured 41.3 mm (n = 36) and 52.8 mm (n = 17) on average, respectively, and had less than two coccygeal joints. The two most reliable methods enable valid comparison to the best practice recommendations.