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What is flystrike and what is the RSPCA’s view on mulesing and flystrike prevention in sheep?

Mulesing was developed in 1929 and, because it is highly effective in preventing flystrike, it has been a routine surgical husbandry procedure for the majority of sheep in Australia to this day. Sheep, especially Merinos, have woolly wrinkles and folds in their skin, particularly around the tail and breech area (back and top of hind legs under tail), which can become moist with urine and contaminated with feces. Blowflies are attracted to this moist area where they lay eggs. Eggs generally hatch into larvae (maggots) within 12-24 hours and feed off the flesh of the sheep for up to 3 days— this is called flystrike, which, if left untreated, is fatal.

Mulesing is a painful procedure that involves cutting crescent-shaped flaps of skin from around a lamb’s breech and tail using sharp shears designed specifically for this purpose. The resulting wound, when healed, creates an area of bare, stretched skin. Because the scarred skin has no folds or wrinkles to hold moisture and feces, it is less likely to attract blowflies. This makes mulesed sheep less susceptible to flystrike in the breech area.

Mulesing is usually carried out during lamb ‘marking’ when the lamb is between 6 to 10 weeks of age. Lamb marking may not only include mulesing but a series of other painful procedures that are all carried out at the same time: tail docking, castration (removing testicles in ram lambs), ear notching or ear tagging, and vaccinating. In 2016-17, an estimated 13.5 million Merino lambs were marked with the majority of these lambs being mulesed.

Mulesing is performed without anaesthesia, and pain relief is not always used. The operation is quick; however the acute pain is long lasting – at least up to 48 hours or from several days to several weeks. The resulting wound bed takes 5-7 weeks to completely heal. Mulesed lambs will socialise less, lose weight in the first two weeks post mulesing, exhibit behavioural indicators of pain including prolonged hunched standing and less time lying and feeding, and stand in a hunched position. The effect on gait and growth may be apparent for up to three weeks following the procedure. Following mulesing, lambs may avoid humans and, in particular, the person who carried out the procedure, for a period of 3 to 5 weeks. This avoidance behaviour is indicative of fear and the extent to which the animal experiences the procedure as aversive.

Both mulesing and flystrike cause substantial challenges to sheep welfare. Mulesing is a quick and effective method of controlling flystrike in Merino sheep, hence its popularity with producers. However, mulesing results in poor welfare both during and after the procedure.

The RSPCA believes that it is unacceptable to continue to breed sheep that are susceptible to flystrike and therefore require an on-going need for mulesing (or other breech modification procedure, e.g. ‘steining’ using liquid nitrogen) to manage flystrike risk.

The RSPCA urges the wool industry to continue to invest research, development and extension effort into a comprehensive flystrike-resistant sheep-breeding program. On-farm extension to facilitate the rapid adoption of breeding solutions must be a priority for the wool industry.

The RSPCA urges retailers sourcing Australian wool to indicate to suppliers their intention to purchase only non-mulesed wool within the shortest possible time frame, noting that such wool should be sourced from flystrike-resistant sheep.

In the meantime, it is important that the wool industry shows progress in relation to adoption of improved management and breeding practices i.e. a steady decline in the number of sheep being mulesed (or subjected to other breech modification) as a proportion of the total flock (Merinos versus non-Merinos).

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Updated on October 18, 2019
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