A wide variety of substances have been used to anaesthetise invertebrates, but many are not anaesthetics and merely incapacitate animals, rather than preventing pain. Much is now known about the mode of action of modern clinical and veterinary anaesthetics because of their use on human beings and other vertebrates. In essence, the role of an ideal general anaesthetic is to act as a muscle relaxant, an analgesic, an anaesthetic and an amnesic. To achieve all these properties with a single substance is difficult and various adjuvants usually need to be administered, resulting in a cocktail of drugs. In a clinical setting, the vast majority of patients are unaware of surgery being carried out and have no memory of it, so they can claim to have felt no pain, but this is much more difficult to demonstrate in invertebrates. Here we show that 1% MgCl2, a muscle relaxant, is a useful adjuvant for the clinical anaesthetic isoflurane on Octopus vulgaris when applied for 10 minutes before the clinical anaesthetic. After this, full anaesthesia can be achieved in 5 minutes using only 1% isoflurane and from which full recovery takes place rapidly in about 10 to 15 minutes. This reduces stress on the animal and minimises the quantity of anaesthetic used.

The use of pain relief during castration and dehorning of calves on commercial beef operations can be limited by constraints associated with the delivery of analgesic agents. As topical anaesthetic (TA) and buccal meloxicam (MEL) are now available in Australia, offering practical analgesic treatments for concurrent castration and dehorning of beef calves, a study was conducted to determine their efficacy in providing pain relief when applied alone or in combination. Weaner calves were randomly allocated to; (1) no castration and dehorning / positive control (CONP); (2) castration and dehorning / negative control (CONN); (3) castration and dehorning with buccal meloxicam (BM); (4) castration and dehorning with topical anaesthetic (TA); and (5) castration and dehorning with buccal meloxicam and topical anaesthetic (BMTA). Weight gain, paddock utilisation, lying activity and behaviour following treatment were measured. CONP and BMTA calves had significantly greater weight gain than CONN calves (P < 0.001). CONN calves spent less time lying compared to BMTA calves on all days (P < 0.001). All dehorned and castrated calves spent more time walking (P = 0.024) and less time eating (P < 0.001) compared to CONP calves. There was a trend for CONP calves to spend the most time standing and CONN calves to spend the least time standing (P = 0.059). There were also trends for the frequency of head turns to be lowest in CONP and BMTA calves (P = 0.098) and tail flicks to be highest in CONN and BM calves (P = 0.061). The findings of this study suggest that TA and MEL can improve welfare and production of calves following surgical castration and amputation dehorning.