Docked tail length in lambs: why the third joint or longer?
A recent survey of Merino husbandry practices in Australia indicates that almost half (44%) of producers are tail docking lambs at the second joint or shorter.
Why is this a problem?
The answer to this question can be found in research conducted by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia in the 1930s and 1940s.
In the research by the CSIRO several different tail lengths were described and tested, including:
long tails, which were about 3.75-4 inches (9.4-10 cm) long or in which the end of the tail extended half an inch (1.3 cm) below the lower border of the breech bare area
medium-long tails, in which the end of the tail extended to just below the lower tip of the vulva but did not extend beyond the lower edge of the breech bare area
medium tails, which were about 2 inches (5 cm) long or in which the end of the tail was opposite the mid-point of the vulva orifice but did not extend below the lower tip
short tails, which did not extend below the upper edge of the vulva.
Undocked tails were also investigated.
The CSIRO research included six studies that investigated the most appropriate tail length for Merino sheep. These studies included more than 10,000 sheep on five properties in eastern Australia and clearly demonstrated that docking the tails of Merino sheep either medium-long or long gave better protection against breech fly strike than docking to give a medium length or short. Leaving the tail undocked also provided better protection against breech fly strike than docking to give a medium length or short tail.
Docking the tails of unmulesed sheep at the second joint or shorter resulted in an inferior result, with these animals experiencing two to three times the rate of breech fly strike as sheep with the tails docked long or medium-long.
Short and medium length tails took longer to heal than medium-long or long tails and were more likely to be infected.