A pilot study to assess whether high expansion CO₂-enriched foam is acceptable for on-farm emergency killing of poultry

Abstract

This pilot experiment was conducted to ascertain whether CO₂-enriched high expansion foam could be an acceptable and efficient alternative in emergency killing of poultry. This method could have wide-ranging applications but with particular emphasis on small (backyard) flocks, free-range sheds or open (naturally-ventilated) housings. The objectives of the study were as follows: 1) to determine whether the injection of foam and being covered with foam leads to fear or panic reactions in birds; 2) to determine the time taken to render birds unconscious and dead and 3) to determine whether any pathological abnormalities are observed post mortem. Six laying hens were individually exposed to increasing levels of CO₂ foam with an expansion rate of 300:1. The test box containing individual birds filled with foam within 30 s. During foaming, two out of six birds tried to escape from the test box (1–2 attempts per bird). Apart from displaying greater alertness, birds showed no aversive reactions to the CO₂ foam. Twenty-to-thirty seconds after being covered with foam, five of the six birds demonstrated one or two forcable or convulsive movements. Movement patterns and muscle jerks immediately following this convulsive movement led us to believe that birds lost consciousness at this moment and, within approximately three minutes, all birds had ceased to have a heartbeat. Macroscopic post mortem examination of the birds revealed no abnormalities and microscopic examination showed moderate bronchiolar bleeding and a small amount of alveolar bleeding. After assessing behavioural parameters, measurements of heart rate and pathological data, it is our conclusion that CO₂ foam has the potential to be an acceptable method of killing poultry. It is advisable for this method to be examined on a larger scale in order to assess the implications of physiological (EEG and ECG) measurements on welfare.