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Evaluation of euthanasia of sheep with intravenous saturated salt solutions to enable the collection of whole, intact brains

Published online by Cambridge University Press:  01 January 2023

KJ Stanger ,
NJ Kells ,
AD Fisher ,
T Jubb ,
J-L Rault  and
C Johnson
KJ Stanger*
Affiliation:
University of Melbourne, Faculty of Veterinary and Agricultural Sciences, 250 Princes Highway, Werribee, VIC 3030, Australia
NJ Kells
Affiliation:
Animal Welfare Science and Bioethics Centre, Massey University, New Zealand
AD Fisher
Affiliation:
Animal Welfare Science Centre, University of Melbourne, Australia
T Jubb
Affiliation:
Livestock Health Systems Australia, Bendigo, Australia
J-L Rault
Affiliation:
Institute of Animal Welfare Science, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Austria
C Johnson
Affiliation:
Institute of Veterinary, Animal and Biomedical Science, Massey University, New Zealand
*
* Contact for correspondence: [email protected]
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Abstract

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Captive bolts or firearms are unsuitable for euthanasia of livestock when an intact brain is required for diagnostics. Injectable barbiturates can be used, but this method carries risk of poisoning animals eating the carcase. Intravenous saturated salt solutions have been used to euthanase heavily sedated ruminants and are cheap, readily available and not a risk to scavenging animals. However, there is concern that they may be painful or cause distress to animals that are not unconscious. This study aimed to determine the suitability of saturated salt solutions, in combination with xylazine, as a method of euthanasia of ruminants using a sheep model. Thirty-two sheep were sedated with xylazine (0.4 mg kg-1 IM) and euthanased with an intravenous overdose of pentobarbitone (PENT; n = 10), saturated potassium chloride (KCL; n = 11) or saturated magnesium sulphate (MGS; n = 10). Time until end of rhythmic breathing and cardiac arrest, and movement events were recorded. Conscious perception of pain was evaluated by measuring cortical brain activity by electroencephalography (EEG). There was no evidence of perceived pain or unpleasant sensory experience for any treatment as indicated by P50, P95 and Ptot and so all methods were deemed humane. Time until transient EEG was comparable for all treatments. Time until onset of isoelectric EEG was prolonged for KCL. Animals euthanased with KCL consistently exhibited severe reflex movements during infusion (eg kicking, convulsion). No severe movement events were observed in animals euthanased with MGS, hence, physiological and movement data support the preferential use of MGS over KCL.

Keywords

animal welfareelectroencephalogramintravenous euthanasiamagnesium sulphatepotassium chlorideruminant
Type
Articles
Information
Animal Welfare , Volume 28 , Issue 4 , November 2019 , pp. 397 - 406
Copyright
© 2019 Universities Federation for Animal Welfare

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