Humane killing of nonhuman animals for disease control purposes

Reports and guidelines produced by international institutions such as the World Organization for Animal Health (OIE, 2005) describe various methods of killing nonhuman animals. Selection and implementation of a killing method may involve several factors. Preventing or minimizing risk to human health and safety may override animal welfare concerns if the disease has the potential to cause high mortality, for example, highly pathogenic avian influenza. Owing to the public health significance of this disease, the scope of this article presents only an overview of the welfare and practical aspects of large-scale killing of poultry on farms. Killing poultry in houses using a gas mixture eliminates the need for human contact with infective materials and birds. Several protocols for administering gas mixtures into poultry houses have been evaluated, mainly in Europe and North America. Overdose of anesthetics in feed and water has sedated birds kept under free-range or semi-intensive rearing systems. Containerized gas killing systems have proved successful on small-to-medium-size poultry farms. However, using nitrogen, a nonaversive gas, could greatly improve bird welfare.