Different carbon dioxide concentrations and exposure times in

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					OR.11.08


    Influence of CO2 stunning on EEG, catecholamines and clinical reflexes of slaughter pigs
             JÖRG HARTUNG1, THEDA VON MÜFFLING2, BERNHARD NOWAK2
1
 Institut for Animal Hygiene, Animal Welfare and Behaviour of Farm Animals, Bünteweg 17p, 30559 Hannover
                 2
                   Institute for Food Quality and Safety, Bischofsholer Damm 15, 30173 Hannover
            University of Veterinary Medicine Hannover, Foundation, Germany, itt@tiho-hannover.de

Introduction                                            atmosphere of 90 vol. % CO2 compared to 80 vol.
Approximately 240 million pigs are slaughtered in       %.
the EU countries per year. Slaughter is bleeding of
an animal to induce death after stunning. This is a     Discussion and Conclusions
statutory requirement. The most common stunning         A concentration of at least 90 vol. % CO2 should be
methods use electricity or carbon dioxide (CO2).        applied when stunning pigs for slaughter. It seems
Since CO2 stunning requires less handling of the        necessary to look in greater detail in the effects of
animals and usually allows stunning of more             CO2 stunning on the well-being of pigs. It is to
animals per hour than electrical stunning, it has       consider whether pre-stunning using an anaesthetic
become quite popular in many countries. The EU          gas should be applied in order to avoid or reduce
directive 93/119/EC permits stunning with an            suffering of the animals in the initial phase when
atmosphere containing at least 70% CO2 by volume        exposed to the CO2 atmosphere. Proper stunning
in air for a minimum of 70 s, in Germany the law        will also improve meat quality.
requires at least 80% CO2. However, there are
observations that after stunning with 80% CO2 for       References
70 s some animals still show signs of consciousness     Anonymous (1993). Council Directive on the
before exsanguination. Therefore experiments were       protection of animals at the time of slaughter or
carried out to measure pig responses to CO2             killing.
atmospheres of both 80% and 90%.                         EFSA (2004): Report on welfare aspects of animal
                                                        stunning and killing methods.
Materials and Methods                                   Hartung, J. et al. (1997). Dtsch. Tierärztl. Wschr.
A total of 460 pigs were stunned with CO2 in a          104, 66-68.
German slaughterhouse with a one-gondola dip-lift       Hartung, J.et al. (2002). Dtsch. Tierärztl. Wschr.
system. The animals were immediately brought into       109, 135-139.
the CO2 atmosphere at maximum concentration.            Raj, M. (1999). Vet. Rec. 144, 165-168.
The floor of the gondola reached the bottom of the      Troeger, K., Woltersdorf (1991). Fleischwirtschaft
pit in 22 s and returned to the ejection level 25 s     71, 1063-1068.
later. Investigations were carried out during the       Velarde, A. et al. (2000). Vet. Rec. 146, 65-68.
normal slaughter routine. The response of the pigs
to CO2 such as catecholamines (adrenalin, AD, nor-
adrenalin, NAD) and lactate in the blood as well as     Tab. 1: Clinical reflexes
clinical reactions (nasal septum and corneal reflex,                          directly        during
heart rate) were investigated. Special EEG-                                   after tip-out   de-bleeding
electrodes were adapted on some pigs for the
                                                                             CR NR HB        CR NR HB
measurement with a mobile data logger. The CO2                                 -      -
concentrations were measured continuously close to      80 Vol. % CO2                      +   +    +     +
                                                                               -      -    -   -    -     -
the head of the pigs when transported up and down       90 Vol. % CO2
in the stunning gondola.                                CR: corneal reflex; NR: nose reflex; HB: heart beat
                                                        + = present
Results                                                 - = absent
The results show that the exposure of pigs to a CO2
atmosphere of 80 vol. % for 70 s is not sufficient
for a proper stun. A number of animals still showed
typical reactions in the EEG (delta activities).        Tab. 2: Catecholamines and lactate in blood plasma
Clinical reflexes were seen regularly during de-                of pigs before and after CO2-stunning
bleeding (Tab. 1). When 90 vol. % CO2 is applied,                 before stunning        in sticking blood
most animals seem to be already dead before de-                      Ad Nad La          Ad        Nad La
bleeding starts. This may create concerns in regard                (ng/l) (ng/l) (mmol/l) (ng/l)  (ng/l) (mmol/l)
to meat hygiene. In the sticking blood very high        80 Vol% CO2 90 320         1.4    131400 252600 10.8
concentrations of catecholamines were found after       90 Vol% CO2 146 395        1.2    112.600 228100 7.1
both applications (80 and 90 vol. % CO2) which          Ad: adrenalin; Nad: noradrenalin; La: lactate
were 1000 times higher than in the same pigs
waiting in the lairage (Tab. 2). These values are
even 10 times higher than after electrical stunning.
Lactate levels are lower after exposure to an