Evaluation of Two Compressed Air Foam Systems for Culling Caged Layer Hens

Reliability of water-based medium-expansion foam as a depopulation method for nursery pigs and cull sows

Animal disease preparedness plans including depopulation guidelines are paramount to prevent the spread of emerging infectious diseases but difficult to implement for swine under field conditions. However, water-based foam (WBF) is currently an approved and successfully deployed depopulation methodology in poultry. Therefore, the reliability of WBF as a depopulation method and the effectiveness and irreversibility of consciousness and consequential mortality in pigs of different ages was assessed across two trials. Trial 1 investigated the time to loss of consciousness and cessation of cardiac activity in nursery pigs (n = 72) at six different foam immersion time points (2.5, 5, 7.5, 10, 12.5 and 15 min) when placed in a 1.47 m³ (1.2 × 1.2 × 1.02 m, length × width × height) plastic bulk container. One pig per replicate was implanted with an ECG bio-logger. Irreversible loss of consciousness was observed after a 5-min immersion. The average (SD) time to development of a fatal arrhythmia from the initiation of the foam application was 7.3 min (1.82 s). Trial 2 aimed to validate the findings from Trial 1 in 75 larger cull sows across three replicates (n = 25). Sows were loaded into a 41-m³ sealed trailer (12.2 × 1.5 × 2.24 m), immersed in WBF and left undisturbed for 5 min post foam-filling completion. Six pigs in each replicate were implanted with an ECG bio-logger. A 5-min dwell time resulted in irreversible loss of consciousness and subsequent mortality in all cull sows. The average time (SD) to cessation of movement and fatal arrhythmia post foam-filling completion was 2.2 min (34.8 s) and 8.7 min (138.0 s), respectively. While a 5-min immersion in WBF induced irreversible loss of consciousness and death in both trials, a 7.5-min dwell time followed by observation for confirmation of death post WBF removal would be advisable for pigs of all sizes.

Evaluation of a Water-Based Medium-Expansion Foam Depopulation Method in Suckling and Finisher Pigs

Simple Summary

The need for effective and efficient means of mass depopulation of swine is critical, given foreign animal diseases, natural disasters, and other hazards that threaten swine production. Mass depopulation methods that can be applied to swine at all ages under field conditions are important due to the varying sizes and differing handling methods across the stages of swine development. The American Veterinary Medical Association Guidelines for Mass Depopulation contain limited options for procedures under constrained circumstances that can be applied rapidly across all sizes of pigs. Previous work has shown that water-based foam can be as effective as carbon dioxide for adult swine depopulation, but without CO₂ supply, expensive equipment, and potential human health hazards. The present study demonstrates that water-based foam is also effective for depopulating, in suckling (18 to 24 days) and finisher (63 to 100 days) pigs. When combined with previous findings, water-based foam is a depopulation method that can be applied rapidly and effectively to all ages in the swine production cycle.

Abstract

The threat of foreign animal disease introduction through contaminated animal products, feed ingredients, and wildlife vectors have highlighted the need for additional approved methods for mass depopulation of swine under emergency scenarios, especially methods that can be applied to pigs across all production phases. The market disruption within the swine industry due to the SARS-CoV-2 pandemic has demonstrated this lack of preparation. The objective of this study was to validate water-based foam as a mass depopulation method for suckling (18 to 24 days of age) and finisher stage (63 to 100 days of age) pigs. Finisher pigs (n = 31, originally 32 but one finisher pig died prior to foaming), allocated as 9 triads and 1 set of 4 pigs, in 10 total replicates, and suckling pigs (n = 32), randomly allocated to two replicates, were completely covered in water-based medium-expansion foam for a 15-min dwell time in a bulk container. Container fill time for the trials were 6.5 ± 0.68 s and 5.3 ± 0.03 s for finisher and suckling pig replicates, respectively. Average (± SD) time for cessation of movement was 105 ± 39.1 s (s) for finisher pigs and 79.5 ± 10.5 s for suckling pigs. After completion of the 15-min dwell time in the foam, all pigs were confirmed dead upon removal from the container. The results from the present study suggest that the use of water-based foam can be an effective means of mass depopulation for suckling and finisher stage pigs, supporting previous research on the application to adult swine.

Comparison of Gaseous and Water-Based Medium-Expansion Foam Depopulation Methods in Cull Sows

Simple Summary

In the face of a swine health crisis, emerging zoonotic diseases or environmental catastrophe, the mass depopulation of swine may be required to prevent the additional spread of disease and to minimize animal pain or suffering. Due to the increasing risk of global disease outbreaks, the U.S. swine industry needs feasible guidelines in place in preparation for such events. Current American Veterinary Medical Association (AVMA) approved swine depopulation methods can be difficult to implement under field conditions. Emergency depopulation using inhalants such as carbon dioxide (CO₂) and nitrogen gas (N₂) or the use of aspirated foam agents have been approved and conducted in poultry in the US, but are not approved for use in other livestock. Our findings, using cull sows, demonstrate that although CO₂, N₂ and aspirated foam combinations successfully killed all the animals, CO₂ and aspirated foam did so in the shortest timeframe. In addition, the use of aspirated foam was as effective as CO₂ for sow depopulation while having potential operational advantages, such as no use of lethal gases and reduced risk of associated equipment failure.

Abstract

The U.S. swine industry is currently inadequately prepared to counteract the increasing threat of high-consequence diseases. Although approved and preferred depopulation guidelines exist, ventilation shutdown (VSD+) is currently the only method being deployed during a state of emergency to depopulate large swine populations. However, the permitted use of VSD+ during constrained circumstances has been criticized due to raised swine welfare concerns. The objective of this study was to investigate the effectiveness of carbon dioxide gas (CO₂), nitrogen gas (N₂), compressed air foam (CAF), compressed nitrogen foam (CAF-N₂) and aspirated foam (AF) during a 15-min dwell time on adult swine in an emergency depopulation situation. A small-scale trial using 12 sows per depopulation method showed the highest efficiency to induce cessation of movement for AF and CO₂ (186.0 ± 48 vs. 202.0 ± 41, s ± SD). The ease of implementation and safety favored AF for further investigation. A large-scale field study using AF to depopulate 134 sows in modified rendering trailers showed a mean fill time of 103.8 s (SD: 5.0 s) and cessation of movement of 128.0 s (SD: 18.6 s) post filling. All sows were confirmed dead post-treatment for both trials. The implementation of AF in modified rendering trailers may allow for a safe and reliable method that allows for the expedient and mobile depopulation of both small and large numbers of sows during an emergency.

Euthanasia of laying hens: an overview

Euthanasia of an animal requires that its death occurs in as humane a manner as possible. There are three key scenarios for euthanasia in the egg industry: the humane destruction of day-old male chicks, euthanasia of individual birds, and the depopulation of flocks for disease control or because conventional transport and slaughter is uneconomic. For day-old chicks, instant mechanical maceration, although conditionally humane, presents a public perception problem. Submerging in CO2 gas is less confronting but is thought to be aversive to animals unless more expensive and harder to manage inert gases are incorporated. Future technologies involving pre-hatching sex determination or sex selection may largely solve the problem when fully developed. For the euthanasia of individual birds within the flock, manual cervical dislocation has been shown to be humane when performed by trained personnel who are willing to perform the procedure. Penetrating and non-penetrating mechanical devices that cause irreversible brain trauma are becoming more available and represent a humane alternative to cervical dislocation when properly placed and maintained. These devices may be less confronting for some staff to use than is cervical dislocation. For whole-flock euthanasia, the overwhelming requirements of disease control and public safety may override considerations of euthanasia. Whole-shed CO2 (or other gas combinations) and foam-based alternatives can be used, but have challenges in commercial settings. Modified atmosphere killing units or low atmospheric stunning systems are alternatives that overcome some of these practical problems, but do require birds to be handled.

Electroencephalographic, physiologic and behavioural responses during cervical dislocation euthanasia in turkeys

Background

There is a critical need to develop appropriate on-farm euthanasia methods for poultry species. Euthanasia methods should affect the brain first causing insensibility, followed by cardiorespiratory arrest. Neck or cervical dislocation methods, either manual (CD) or mechanical (MCD), are reported to cause a prolonged time to loss of sensibility and death with inconsistent results upon application, especially MCD methods. However, there is limited information on cervical dislocation in turkeys. The overall objective of this study was to assess the welfare implications of CD and a newly developed MCD device for euthanasia of cull turkeys in comparison with intravenous (IV) pentobarbital sodium (1 mL/4.5 kg), the gold standard euthanasia method. Time to death using electroencephalographic (EEG) and behavioural responses were monitored in eight and eighteen week-old turkeys for five minutes after each euthanasia method application. Spectral analyses of EEG responses and onset of isoelectric EEGs were compared to baseline EEG recordings of birds under anesthesia and behavioural responses were studied among euthanasia treatments. A significant decrease in brain activity frequencies analysis and isoelectric EEG were recorded as time of brain death.

Results

All turkeys euthanized with IV pentobarbital sodium presented a rapid and irreversible decrease in the EEG activity at approximately 30s post-injection with minimal behavioural responses. CD and MCD methods caused EEG responses consistent with brain death at approximately 120 s and 300 s, respectively. Additionally, isoelectric EEGs resulted in all pentobarbital sodium and CD groups, but only in 54 and 88% of the eight and eighteen week-old turkeys in the MCD groups, respectively. There were few clear patterns of behavioural responses after CD and MCD application. However, cessation of body movement and time to isoelectric EEG after CD application were positively correlated.

Conclusions

Use of CD and MCD resulted in a prolonged time to death in both age groups of turkeys. MCD application presents a number of welfare risks based on electroencephalographic and behavioural findings. Intravenous pentobarbital sodium induced rapid brain death, but possesses several on-farm limitations. To develop improvements in cervical dislocation methods, further investigations into combined or alternative methods are required to reduce the prolonged time to insensibility and death.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-1885-x) contains supplementary material, which is available to authorized users.