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Under most modified atmosphere killing methods, euthanasia occurs close to where birds have been kept, cutting down on handling and reducing the stress associated with transport.
on July 23, 2015

The advantages of on-farm spent hen disposal using MAK

Modified atmosphere killing can offer a cost-effective method for the disposal of spent layer hens, but rules must be followed to gain maximum, long-term benefit.

The use of modified atmosphere killing to dispose of spent layer hens on farm could offer significant advantages for egg producers, a research project supported by Australia’s Poultry CRC has found.

The study compared the practical options for, and advantages and disadvantages of, on-farm killing, and modified atmosphere killing was found to be the most feasible and acceptable method to be used by the Australian layer industry.

Some 25 percent of Australia’s egg farmers are already using the method. However, to date, there have been no standardized procedures available for the practice, with farmers following their own protocols. 

The Poultry CRC commissioned the Australian Egg Corporation (AECL) to manage the project, called Development and Extension of Industry Best Practice for On-Farm Euthanasia of Spent Layer Hens, and work was conducted by the animal and avian health consultancy Scolexia.

A literature review was conducted, and modified atmosphere killing was then evaluated by observing field operations.

While many positives to the current use of modified atmosphere killing on farm were noted, problems in its implementation were found. Among these were that there was often inadequate pre-planning with regard to people resources and uncertainly about the CO2 required. Inadequate pre-training of staff and a lack of familiarization with procedures, in particular welfare requirements and obligations, was also noted.

Based on the findings, modified atmosphere killing field trials were then undertaken and, from these, improvements in methodology were developed, involving container design, the objective recording of CO2 concentrations, and the improved delivery of gaseous CO2.

The resultant case study should assist the egg industry to undertake efficient and welfare sensitive mass destruction of spent layer hens. By following this case study, consistency and best practice could be ensured across the egg sector, and the wider community could have confidence that the procedures are humane, Scolexia argues.

Time and cost benefits

Commenting on their findings, Scolexia’s Peter Scott said: “What was immediately identified by producers was that the actual operation costs of on-farm depopulation using CO2 were not only less than using traditional methods and collection from farm for processing, but significantly more flexible.

“Using pre-planned crews and dead bird collection vehicles, entire sheds could be depopulated in a morning, rather than dispersed over two to three days when picking up for processing.

“This resulted in a significant saving in labor costs, and improved strategic use of labor. More importantly, the depopulation could be done at a time selected and logistically preferred by the layer producer.” 

Australian egg industry situation

Any disruption to the timing of depopulation is costly, and can create operational difficulties for the producer by affecting egg flows. For those farmers who use off-farm processing plants for spent hen disposal, this can be a significant issue, as these plants are limited in their capacity, and this can lead to logistical difficulties.

In the Australian context, implementing the most practical method for on-farm euthanasia has become increasingly pressing. A number of spent layer processing plants in the country have closed, in part due to the uneconomical nature of hen meat production, and the costs that processors had to charge producers in order to remain viable.

The distance from the processing plants has also become an issue in spent hen disposal, particularly with the introduction of the country’s Land Transport of Poultry code, which means that birds cannot be transported for longer than 24 hours.

Those egg farmers that are already using modified atmosphere killing to dispose of spent hens have been using portable bins and following their own protocols, however, if the method is to be more widely used by the egg industry, it must be shown to be sustainable and humane.

Findings and recommendations

Given adequate exposure time, 40 percent CO2 in air is sufficient to kill spent layers, but concentrations above 55 percent will kill birds more quickly. In all cases, it should be standard practice to assure that adequate concentrations of CO2 are available, and that all equipment is functioning properly prior to beginning procedures.

CO2 causes the swift onset of anesthesia and subsequent death. Poultry can be euthanized using CO2 gas by being placed in containers that are sufficiently airtight to maintain CO2 at desired levels. To meet the requirements for humane euthanasia, birds already in the container must be unconscious before being overlain by other bids, and unconsciousness must be maintained until death occurs.

Regarding the materials and equipment needed for successful modified atmosphere stunning, Scolexia recommends:

  • An appropriate size container with viewing windows. Capacity may vary from 200-1,500 birds.
  • Forklift/tractor to lift and mover the containers.
  • Divider pens for floor system and carts for cage system.
  • Appropriate number of CO2 cylinders.
  • Gas delivery hose, preferably made of non-freeze flexible material.
  • CO2 pre-heater to heat the gas at the regulator to avoid freezing the gas delivery system.
  • Proper monitoring device, preferably an electronic CO2 meter with or without data logging.
  • Materials for wash down and sanitation of the equipment.

It also notes that staff need to be suitably trained if some of the problems seen during its observations of how modified atmosphere killing is used for spent hen disposal are to be prevented:

  • Farm staff must be familiar with handling domestic poultry and have an awareness of good animal welfare practices.
  • Staff should wear protective clothing and footwear.
  • Proper training of personnel is essential to ensure birds are appropriately euthanized.
  • Farming senior manager acting in supervisory role.

Regarding the container in which birds are to be euthanized, there are basic design criteria that need to adhered to. The container must:

  • Be easy to load 
  • Ensure fast and effective euthanasia 
  • Permit easy carcass removal and disposal 
  • Be simple to wash down and sanitize inside and out 

The Poultry CRC has recently been running workshops on modified atmosphere killing for spent hen disposal and published the manual Modified Atmosphere Killing, and the AECL will review the integration of the standard operating procedures that have come from the study into its own quality assurance program. 

CO2 causes the swift onset of anesthesia and subsequent death. Poultry can be euthanized using CO2 gas by being placed in containers that are sufficiently airtight to maintain CO2 at desired levels.
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