Disease control measures require poultry to be killed on farms to minimise the risk of disease being transmitted to other poultry and, in some cases, to protect public health.

In a paper published in Poultry Science, Dorothy McKeegan of the University of Glasgow in the UK and co-authors there and at Wageningen UR in the Netherlands as well as Livetec Systems Ltd. and the Royal Veterinary College in the UK report their assessment of the welfare implications for poultry of the use of high-expansion gas-filled foam as a potentially humane, emergency killing method.

They explain that, in laboratory trials, broiler chickens, adult laying hens, ducks and turkeys were exposed to air-, nitrogen- or carbon dioxide-filled high expansion foam (expansion ratio 300:1) under standardised conditions. Birds were equipped with sensors to measure cardiac and brain activity, and measurements of oxygen concentration in the foam were carried out.

Initial behavioural responses to foam were not pronounced but included head-shakes and brief bouts of wing-flapping. Both nitrogen- and carbon dioxide-filled foam rapidly induced ataxia/loss of posture and vigorous wing-flapping in all species, characteristic of anoxic death.

Immersion in air-filled, high expansion foam had little effect on physiology or behaviour, the researchers report.

Physiological responses to both nitrogen- and carbon dioxide-filled foam were characterised by a pronounced bradyarrythymia and a series of consistent changes in the appearance of the electroencephalogram.

These were used to determine an unequivocal time to loss of consciousness in relation to submersion. Mean time to loss of consciousness was 30 seconds in hens and 18 seconds in broilers exposed to nitrogen-filled foam, and 16 seconds in broilers, one second in ducks, and 15 seconds in turkeys exposed to carbon dioxide-filled foam.

Euthanasia achieved with anoxic foam was particularly rapid, which is explained by the very low oxygen concentrations (below one per cent) inside the foam.

Physiological observations and postmortem examination showed that the mode of action of high expansion, gas-filled foam is anoxia, not occlusion of the airway.

McKeegan and co-authors conclude their work provides proof-of-principle that submersion in gas-filled, high expansion foam provides a rapid and highly effective method of euthanasia, which may have potential to provide humane emergency killing or routine depopulation.

Reference

^{McKeegan D.R.F., H.G.M. Reimert, V.A. Hindle, P. Boulcott, J.M. Sparrey, C.M. Wathes, T.G.M. Demmers and M.A. Gerritzen. 2013. Physiological and behavioral responses of poultry exposed to gas-filled high expansion foam. Poult. Sci. 92(5):1145-1154. doi: 10.3382/ps.2012-02587}

June 2013