EEG changes in 4-week-old lambs in response to castration, tail docking and mulesing

Objective To interpret changes in EEG in relation to perceived pain of cast ration, mulesing and docking in lambs. Design Analysis of covariance (randomised block design) to determine the ef fects of treatment on eight bandwidths of the EEG frequency spectrum. Procedure Ninety-eight, 3- to 4-week-old lambs were subjected to one of sev en treatments: castration, tail docking, mulesing, ear tagging, sham sheari ng, formalin injection (to induce lameness) and handling. EEG was recorded for 15 min before treatment, during treatment, and for 15 min after treatme nt. Results Consistently lower mean power values across all bandwidths of the E EG were found at the time of mulesing and docking than at handling and shea ring (P < 0.01). Formalin injection resulted in lower power values than han dling and shearing (P < 0.01). Castration had lower power values than handl ing and shearing. Similarly, for 15 min after treatment, mulesing and forma lin injection had significantly lower power values than handling, shearing, ear tagging and castration (P < 0.05). Conclusion The consistent effects associated with mulesing, docking and cas tration compared to handling, shearing and ear tagging suggest that mulesin g at both the time of treatment and during 15 min after treatment results i n a response that is similar to that of induced lameness. Docking and castr ation result in a response at the time of treatment that is similar to indu ced lameness and mulesing, but during 15 min after treatment is similar to the non-noxious control treatments. However, the depressing effects on the mean power values are the reverse of that anticipated from a previously dev eloped pain model, highlighting the need for further research to develop th is technology to evaluate pain associated with husbandry procedures.