Welfare consequences of mulesing of sheep.

Mulesing is traditionally performed on approximately 80% of Merino wool-producing sheep in Australia. Mulesing produces a stress response that persists for 24 to 48 hours. Behavioural changes indicative of pain and discomfort resolve within 24 and 48 hours, respectively. Reductions in weight gain may persist for 14 days. The acute stress response to mulesing has been shown to be similar to that produced by shearing, castration and mild flystrike, but mulesing has a longer duration of response (24 to 48 hours) than shearing (1 hour) or knife castration (8 to 24 hours), whereas flystrike response persists for the duration of infection. Theoretically, if mulesing were not used, with Merino sheep of existing genetics, increased chemical use and flock inspections could keep flystrike rates to approximately equivalent to present levels in some production systems. Increased handling events for chemical preventative application would represent a mild stressor for sheep, but cumulatively not more than that of mulesing. If producers were able and prepared to sufficiently increase resources into alternative anti-flystrike methods, then the welfare of Merino sheep would probably be equivalent or better to that of today. If constraints such as property size or finances dictate a sub-optimal level of flystrike prevention and treatment, then animal welfare will unquestionably be worse. The result of that equation would depend on individual flock managers, the physical characteristics of their production system, the profitability of their business, and seasonal variations in flystrike risk. It is likely that there would be some occasions when flystrike would increase. This highlights the need for alternative strategies, such as genetic selection, to reduce the susceptibility of Australian Merino sheep to flystrike.