The use of carbon dioxide (CO2) as an alternative euthanasia method for goat kids

Abstract

<p>The dairy industry is faced with the challenge of euthanizing unwanted male offspring in addition to other sick or injured neonates. Carbon dioxide (CO2) may be a potential alternative to current methods. The goat kid served as a model in approach-avoidance and conditioned place aversion paradigms. A preference test box was custom-made with two connected chambers; one chamber held an ambient atmosphere (control) and one maintained a static CO2 concentration (treatment). Kids were allotted 5-minutes in the control chamber before a sliding door was opened, after which kids were given 10-minutes access to the treatment chamber. The objective of the first study was to determine the ability of kids to move from the control to the treatment chamber to access a milk reward, and the effect of an olfactory or visual stimulus on learning. All kids (n=24) exhibited learning, and latencies to enter, touch the milk bottle, and suckle decreased over day (P<0.0001). Milk consumption increased over days (P<0.0001), and startle, bottle engagement, and lying behavior did not differ between days (P>0.05). The presence of an olfactory stimulus (peppermint oil) did not affect learning, and the visual stimulus (plastic curtain) did not prevent learning. The second study examined kids’ tolerance of 10%, 20%, and 30% CO2. Kids (n=12) were randomly assigned 10% or 20% as the first treatment, and were systematically tested with all kids receiving 30% as the last treatment. A 2-day washout (ambient CO2) period occurred between each gas treatment. 10 kids tolerated 10% CO2, while one kid exited the treatment chamber after consuming his full ration, and 1 kid lost posture at 289s. At 20% and 30%, posture loss ranged from 83s to 271s. One kid exited before losing posture at 20%, then re-entered the chamber and became recumbent. Kids did not show avoidance behavior to any CO2 concentration, and did not appear to develop a conditioned aversion. The results of this study show promising results for CO2 as a euthanasia method in goat kids. Further research is required to confirm its suitability, and determine its potential for other ruminant species.</p>