NR AUFS
AU Riesemann,M.E.
TI [Study on hematogenic dissemination of CNS tissue depending on stunning method]
OT Untersuchung zur hämatogenen Streuung von ZNS-Material bei Schlachtrindern in Abhängigkeit der Betäubungsart
QU Inaugural-Dissertation zur Erlangung der tiermedizinischen Doktorwürde der Tierärztlichen Fakultät der Ludwig-Maximilians-Universität München von Maria Elisabeth Riesemann aus Steingaden, München, 15. Juli 2005
IA http://edoc.ub.uni-muenchen.de/archive/00004220/
PT Dissertation
AB
With respect to Bovine Spongiform Encephalopathy (BSE) and the possible transmission of this disease to humans preventive measures to ensure consumer protection have to be taken. Especially contamination with tissue of the central nervous system (CNS) resulting from cattle stunning is associated with a definite risk. In this context, the commonly used conventional method of captive bolt stunning has been subject to criticism whereas electrical stunning is considered a possible alternative. The aim of the present study was the examination of CNS dissemination via blood circulation into inner organs of slaughter animlas after application of these two stunning methods currently approved for stunning cattle in Germany.
In order to be able to directly compare captive bolt and electrical stunning both of the methods were examined in two slaughterhouses. In each of the four slaughterhouses 60 female cows were included in the investigation. Of each animal eight samples were taken, resulting in a total of 1920 individual samples. The following consecutive heart structures were sampled by swabbing: right atrium and ventricle, pulmonary trunk, left atrium and ventricle and aorta. In addition, lung and myocardium tissue samples were taken. The CNS contamination of the samples was analysed using an immunological method based on the detection of a CNS specific marker protein.
Positive results and therefore CNS contamination could be shown in all of the six heart structures sampled by swabbing and also in lung tissue. Therefore, in the case of neural embolism due to stunning a continuous dissemination of CNS tissue along the bloodstream was observed irrespective of the stunning method used. In each positive animal an average of 3.2 individual samples was positive. The number of positive swabs taken from the structures of the left heart, the anatomical location of which is subsequent to blood passage of the lung, was only slightly lower than that of the positive samples originating from the right heart situated prior to pulmonary circulation. Therefore, proof for filtration and resulting dilution of CNS tissue circulating in the blood by passage through the pulmonary capillary system could not be established. The samples taken from the origin of the aorta even showed the second highest contamination rate, which implies that a further dissemination of CNS material via the arterial blood stream is to be expected.
The comparison of the stunning methods showed that in cattle stunned with a captive bolt 29.7% of the individual samples were positive. This large number of samples in which CNS was detected indicates that the risk for the consumer associated with consumption of the by-products heart and lung is not to be neglected. After electrical stunning positive results were also obtained, yet in only 3.6% of the individual mples examined. Therefore, captive bolt stunning was associated with CNS dissemination to a considerably higher extent and also in higher concentrations in comparison to electrical stunning. An animal was considered positive when at least one of the eight individual samples taken from that animal showed a positive result. While in 70.8% of the animals stunned with a captive bolt CNS was detected, only 14.2% of the animals were positive after electrical stunning. In addition, the results were shown to be influenced by external factors as clear variations between slaughterhouses using the same stunning technique occurred, depending e.g. on the method of bleeding and the day of sampling. From this, the necessity of further minimizing the risk of CNS contamination by optimizing stunning technology arises.
In summary, it has to be emphasized that electrical stunning is the only method currently available for stunning cattle with the potential to effectively prevent CNS dissemination. Therefore, the efforts to optimize the use of this technique in routine slaughter should be intensified.
AD Maria Elisabeth Riesemann aus dem Institut Hygiene und Technologie der Lebensmittel tierischen Ursprungs der Tierärztlichen Fakultät der Ludwig-Maximilian-Universität München (Lehrstuhl: Prof. Dr. A. Stolle)
SP deutsch
PO Deutschland