Assessment of on-farm euthanasia methods for pigs weighing 2 to 25 kg

On-farm euthanasia of piglets is an essential practice to alleviate the suffering of animals that are sick, injured, or in severe distress. This study evaluated four euthanasia methods for piglets weighing between 2 and 25 kg (22 piglets weighing between 2 and 8 kg and eighteen piglets weighing between 8 and 25 kg), focusing on physiological responses and behavioral observations to identify humane and effective practices. Percussive blow to the head, penetrating captive bolt, and electrical stunning are currently authorized under European Union regulations, while the fourth method, nitrogen-filled high-expansion foam, is only authorized for piglets weighing between 15 and 41 kg and requires confirmation on its effectiveness in piglets weighing less than 15 kg. Results showed that current methods have limitations, particularly for piglets under 5 kg. The percussive blow to the head resulted in prolonged time to cardiac arrest (mean ± standard deviation: 596 ± 193 s), with no sign of return to consciousness, highlighting the need for a secondary method such as bleeding. Electrical stunning and killing showed inconsistent outcomes during the killing phase due to the small size of the heart, with effectiveness heavily dependent on electrode placement. For piglets over 8 kg, the penetrating captive bolt and electrical stunning provided satisfactory results with mean times to cardiac arrest of 433 ± 60 s and 326 ± 115 s, respectively. Nitrogen-filled high-expansion foam, an emerging method, demonstrated potential as a humane method by inducing anoxia, with a mean time to loss of posture of 17 ± 5 s. Initial behavioral observations highlighted discomfort related to foam exposure and not necessarily linked to nitrogen. Further research is required to confirm its physiological impact and validate its suitability for on-farm use. This study underscores the need to refine existing methods and explore innovative solutions to meet animal welfare standards, societal expectations, and regulatory requirements. Findings contribute to the development of humane, practical, and effective euthanasia protocols, paving the way for improved practices in pig farming.