Short and middle-term consequences
Studies on the consequences of mulesing of the lamb’s behavior and physiology concord to conclude that is results in a substantial welfare insult (review by Fisher, 2011). The stress response, mainly measured through active pain behavior, alteration of the normal behavior and cortisol concentration, is not dissimilar to that of surgical castration but persists longer. In the early studies on the subject, most behavioral changes indicative of pain appear to be resolved by 24h, although discomfort may persist for approximately 48h. Those behavior are mainly increased standing, particulary in a hunched position, reduce lying and grazing, cessation of play and other social interactions. A more recent study has suggested longer-term consequences to mulesing with behavior and physiological indicators modified up to 2 weeks post operation.
It can be also noted that mulesed lamb show a greater avoidance of human beings than non-mulesed lamb until 5 weeks after the operation. This avoidance resumed before 17 weeks after mulesing. This can be associated with an apparent hypersensitivity to other stressors (Lee & Fisher, 2007; Philips, 2009).
The use of anesthetics and analgesics
The use of short-term analgesic or local anesthetics during or immediately after the operation has been shown to have a relatively low efficiency in controlling the pain of the lamb. Providing effective pain relief for sheep following mulesing require the combined use of long and short-acting analgesic (Fisher 2011). The use of pain relief for sheep during mulesing did not seem to be widespread in 2006/2007 (Sneddon & Rollin, 2010). The company Bayer, an anaesthetics and analgesics seller, indicated in 2011 that more than 60% of the mulesed lamb were provided in pain relieves (Bayer Australia Limited, 2011). However, the explanation of this feature is not available (proportion of of long-term/short-term pain relief, duration of the treatment, effectiveness of the doses provided,…).
Long-term consequences
At really long term, mulesing seems to have a positive impact on the welfare of the animal by decreasing its susceptibility to be struck, the time to be shorn and the accidental cuts associated to it and the general handling that is required for its management.