Published on August 13, 2013
Nordic Poultry Conference, Reykjavik, Nov 17th 20th 2009 On farm killing of poultry for disease control and other emergencies C. Berg Department of Animal Environment and Health, Swedish University of Agricultural Sciences, PO Box 234, SE 532 23 Skara, Sweden Introduction Poultry producers are generally well accustomed to killing a limited number of sick, underweight or injured birds on the farm during each production period. Furthermore, in some Nordic countries the killing of spent hens on farm is seen as an alternative to sending the birds off for slaughter. This is the case especially if the farm is located far away from the nearest slaughterhouse, if birds are unfit for consumption or if it is otherwise considered beneficial from an animal welfare point of view to avoid crating and transporting the birds. In such cases, birds are often killed in house using carbon dioxide. Flocks can also be killed using carbon dioxide in so called flow containers placed right outside the building. These situations, however, are for many reasons quite different from the situation that arises when a flock is diagnosed with a contagious zoonotic or epizootic disease causing a request for immediate destruction of the flock in question and possibly also other flocks on the premises, depending on the nature of the disease. Descriptions of various methods for on farm killing can be found in the literature (Berg, 2007; Berg et al., 2007, Gerritzen et al., 2006, Raj, 2008; Raj et al., 2006; 2008). For small flocks at hobby level, methods such as a blow to the head, electrical stunning or captive bolt stunning, all followed by neck dislocation or bleeding (the latter usually discouraged for biosecurity reasons) or injection of barbiturates are often recommended. For commercial flocks, however, these methods would be extremely time consuming and also result in closer contact between infected birds and humans than desired from an occupational hazards point of view. Although the capacity of some versions of containerized gassing systems using carbon dioxide and/or argon gas would be reasonable, there would still remain a need to manually catch and handle the birds. In order to avoid this, the method of choice during a disease outbreak is whenever possible instead to kill the birds inside the house. In house killing of laying hens, broilers and turkeys As mentioned above, whole house killing of spent hens using carbon dioxide gas is a method which has been used for several years, especially in Sweden where approximately 50 flocks of end of lay hens are killed this way every year. This means that the method is listed with detailed provisions in the legislation (Anon., 2007) and that both the gas supplying company and the practicing veterinarians are now reasonably experienced in handling the method. Furthermore, Swedish legislation requires all recently constructed laying hen, broiler and turkey barns to have a gas inlet pipe mounted already during construction, in case of a disease outbreak occurring later.
Practical evidence from these killings show that calculating for 80 % CO2 to be used will result in final in house levels of CO2 high enough to safely kill all birds within reasonable time and also allowing for some gas leakage (Berg, in prep.). Buildings are sealed properly, but some openings are left in or near the ceiling, to allow for air to escape thereby avoiding over pressurizing the building. A relatively narrow pipe inlet is used, fitting a hose of approx 4 cm diameter. The cold gas will then enter the building at high pressure and immediately evaporate and spread in the building. To avoid problems with birds becoming hit by the cold high pressure gas jet, correct positioning of the inlet and the use of proper barriers is crucial (Berg and Yngvesson, 2007). The same method can of course be used when killing flocks for disease control purposes. It has been shown to work well for both loose housed layers, caged layers (three tier systems), broiler and turkeys in disease control situations. It should be acknowledged that carbon dioxide is considered moderately aversive for poultry and will cause respiratory discomfort (Coenen et al., 2009), but this disadvantage has to be evaluated in the perspective of the advantages related to process speed, availability, biosecurity, workers’ safety and so on. Furthermore, carbon dioxide is currently used for stunning broilers and turkeys at a considerable number of slaughterhouses throughout Europe (Coenen et al., 2009, Hänsch et al., 2009). Recent research indicates that using inert gases, such as argon or nitrogen, may not be as beneficial from a bird welfare perspective as previously thought (Coenen et al., 2009; McKeegan et al, 2007). In Denmark, nitrogen gas has been used in trials for in house killing of laying hens, with satisfactory results. Nitrogen can be used also for turkeys. There are on going trials in other European countries looking at developing systems of distributing a lethal gas by using gas filled foam (Gerritzen and Sparrey, 2008). However, no such method is currently commercially available. In the US, standard fire fighting foam is used to suffocate the birds when killing broiler and turkey flocks for disease control purposes (Benson et al., 2007). In Europe, this method is not considered acceptable from an animal welfare point of view. In house killing of ducks and geese As stated above, using carbon dioxide works well not only for killing hens but also for turkeys. In theory, carbon dioxide is lethal also to ducks and geese, and this effect has been demonstrated under experimental conditions, at least for ducks (Gerritzen et al., 2006; 2007). However, practical experience from countries having killed large numbers of geese and also ducks due to AI infection indicates that due to the commonly used design of buildings for these species it is very difficult to arrange such whole house killings in practice. Furthermore, also when killing these birds in containers using CO2, there are reports indicating that the process is too slow to be acceptable from an animal welfare point of view, even if all birds will eventually die. Hence, there has been an interest in developing suitable methods for killing ducks and geese on farm. For small numbers of birds, a swift blow to the head followed by neck dislocation is one possibility; injection of barbiturates another. For large flocks, however, these methods are slow and require large numbers of staff. In any case there are situations where in house killing is definitely to be preferred, for
biosecurity reasons. In the Scandinavian countries, duck and goose sheds are often reasonably stable buildings, where sealing should not be impossible. To evaluate if using nitrogen would be suitable for these species, a number of trials have been carried out. The nitrogen project trials The project, which was founded by the Nordic Council and coordinated by the Danish Ministry of Food, Agriculture and Fisheries (Fødevarestyrelsen), covered on farm killing of turkeys, ducks and geese. During the experimental phase, a number of birds were placed in Perspex test boxes, which were then gradually filled with nitrogen until the level of residual oxygen was equal to or below 2 %. The gas concentration, temperature and the behavioural reactions of the birds were continuously recorded. During the on farm phase, empty commercial houses for ducks, geese and turkeys were used. A number of birds were placed in the respective houses, which had been meticulously sealed, and nitrogen was brought into the buildings via a number of hoses and left to evaporate. Afterwards, birds killed using nitrogen and a number of control birds killed using barbiturates underwent postmortem examinations. The project is now in the finishing phase, results are being analyzed and video footage is being processed. One thing learned from these studies is the importance of developing practical methods for guiding and controlling the nitrogen infusion and vaporization also in very large buildings, to ensure that the oxygen level is rapidly and evenly decreased to desired levels. Furthermore, proper sealing is crucial. Summary There is substantial practical evidence showing that carbon dioxide gas can be used for killing hens, broilers and turkeys in house on farm, in a way that can be considered acceptable from an animal welfare point of view. Also nitrogen gas has been used for killing laying hens in house. The results from the trials described above indicate that nitrogen gas can also be used for killing geese, ducks and turkeys in house, provided that sealing is carefully carried out and that the gas can be evenly distributed in the building. References Anonymous, 2007. Statens jordbruksverks föreskrifter och allmänna råd (SJVFS 2007:77) om slakt och annan avlivning av djur, Saknr L22, 8 kap 19 § (legal text). Benson, E., Malone, G.W., Alphin, R.L., Dawson, M.D., Pope, C.R. & van Wicklen, G.L., 2007. Foam based mass emergency depopulation of floor reared meat type poultry operations. Poultry Science 86:219 224.
Berg, C., 2007. Emergency killing of poultry during disease outbreaks in the Nordic countries. Proceedings XIII International Congress in Animal Hygiene, Tartu, Estonia, ISBN 978 9949 426 32 4, pp 1053 1059. Berg, C., Yngvesson, J., 2007. Avlivning av värphöns i stallet med koldioxid. Fjäderfä nr 7/07, 18 20. Berg, C., Algers, B., Atkinson, S., Dzieciolowski, T., Björnerot, L., 2007. Akut avlivning av fjäderfäflockar vid sjukdomsutbrott. Svensk Veterinärtidning, vol 59, 7:11 19. Coenen, AML., Lankhaar, J., Lowe, JC., McKeegan, DEF., 2009. Remote monitoring of electroencephalogram, electrocardiogram, and behaviour during controllled atmosphere stunning in broilers: implications for welfare. Poult. Sci. 88: 10 19. Gerritzen, MA, Lambooij, E., Stegeman, JA., Spruijt, BM., 2006. Slaughter of poultry during the epidemic of avian influenza in the Netherlands in 2003. Vet. Rec, 159: 39 42. Gerritzen, M., Lambooij, B., Reimert, H., Stegeman, A., Spruijt, B., 2007. A note on behaviour of poultry exposed to increasing carbon dioxide concentrations. Appl. Anim. Behav. Sci., 108: 179 185. Gerritzen, MA and Sparrey, J., 2008. A pilot study to assess whether high expansion CO2 enriched foam is acceptable for on farm emergency killing of poultry. Anim Welfare, 17: 285 288. Hänsch, F., Nowak, B., Hartung, J., 2009. Evaluation of a gas stunning equipment used for turkeys under slaughterhouse conditions. Livest. Sci. 124: 248 254. McKeegan, DEF., Abeyesinghe, SM., MLeman, MA., Lowe, JC., Demmers, TGM, White, RP., Kranen, RW., van Bemmel, H., Lankhaar, JAC., Wathes, C., 2007. Controlled atmosphere stunning of broiler chickens. II. Effects on behaviour, physiology and meat quality in a commercial processing plant. Bri. Poult. Sci., 48 (4): 430 442. Raj, M., 2008. Humane killing of nonhuman animals for disease control purposes. Journal of Applied Animal Welfare Science, 11:112 124. Raj, A.M.M., Sandilands, V. & Sparks, N.H., 2006. Review of gaseous methods of killing poultry for disease control purposes. Veterinary Record, 159: 229 235. Raj, M., O’Callaghan, M., Thompson, K., Beckett, D., Morrish, I., Love, A., Hickman, G. & Howson, S., 2008. Large scale killing of poultry species on farm during outbreaks of disease: evaluation and development of a humane containerized gas killing system. World’s Poultry Science Journal, 64: 227 243.
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