Beschreibung
In Germany, electrical stunning and stunning using carbon dioxide are the approved stunning methods for pig slaughter. However, the latter method is discussed controversially due to the stressful initiation phase for the pigs. In Germany, Council Regulation (EC) No 1099/2009 and the national German regulation on the protection of animals at the time of slaughter (TierSchlV) apply to the electrical stunning of fattening pigs. When applied correctly, electrical stunning immediately leads to a loss of perception and insensibility. Nevertheless, high backup stunning rates (BSR) can still be observed in electrically stunned pigs. The legal standards of electrical stunning were determined under laboratory conditions in 1978. However, the technical conditions in the abattoirs have been further developed since then. In addition, the slaughtered pigs have also changed, because today different crossbreeds and genetic lines with different carcass traits are used. With the present study, key parameters of electrical stunning should be identified that reduce BSR more effectively than the legally prescribed parameters of electrical stunning. In addition, other influencing factors on stunning effectiveness and carcass traits were examined. The focus was on the genetic background of the pigs, which was previously assumed to have an effect on stunning effectiveness.
For this purpose, 12,028 pigs of different genetic lines, divided into the slaughter groups of organic pigs (Bio), Swabian-Hall pigs and crossbreed pigs (SHV, German: Schwäbisch-Hällisches Schwein) and white fattening pigs (WS) were slaughtered in a southern German abattoir over a period of more than 14 months with different key parameters of electrical stunning. Stunning settings with a current flow time of 1 s were summarized as stunning program (SP) A, those with a current flow time of at least 4 s under SP-B.
As a result, a BSR of 2.71 % was determined for SP-A, which met the requirements of the Council Regulation (EC) No 1099/2009 and the recommendations of European Food Safety Authority (EFSA). For SP-B, which corresponded to the national German regulation on the protection of animals at the time of slaughter (TierSchlV) and the Handbuch Tierschutzüberwachung bei der Schlachtung und Tötung (Status March 2017) by the AG Tierschutz der Länderarbeitsgemeinschaft Verbraucherschutz (LAV) the BSR was 5.79 %. According to the recommendations of the Training and Consultancy Institute for animal welfare at transport and slaughter (bsi) Schwarzenbek, the BSR should not exceed 1 %. Although SP-A needs improvement, the BSR was around half and highly significantly (p < 0.0001) lower than BSR with SP-B. In addition, the stunning electrode position had a highly significant (p = 0.0001) and slaughter group a significant (p = 0.0021) effect on the stunning effectiveness. However, the stunning effectiveness was not significantly influenced by the arrival time at abattoir (p = 0.2452) or by the distance from farm to abattoir (p = 0.2480). Regarding the slaughter groups, BSR for the Bio-pigs was 5.36 %, 3.69 % for the SHV-pigs and 3.16 % for the WS-pigs respectively. BSR of the Pig Improvement Company Deutschland GmbH (PIC) x Pietrain (Pi) genetic line were significantly lower compared to those of the German Landrace (DL) x Pi, Large White (LW) x DL x Pi and white Swabian breed (SH; Swabian-Hall pig, German: Schwäbisch-Hällisches Schwein) x Pi. The results demonstrate the influence of the genetic background of the pigs on the stunning effectiveness, since pigs of the genetic line PIC x Pi were represented in the slaughter group of Bio-pigs and WS-pigs, were stunned with SP-A and SP-B and derived from different farms. The pH40 in the semimembranosus muscle (pH-SM40) was also highly significant (p < 0.0001) influenced by the slaughter group, the genetic background of the pigs, their farm of origin, the SP A/B used, the outside temperature on the day of slaughter and the interaction slaughter group / SP-A/B and significantly (p = 0.0025) influenced by the period of delivery of the pigs to the abattoir. For instance, the pH-SM40 in SHV-pigs was significantly higher than in Bio-pigs (6.58 vs. 6.40; p = 0.0343) or WS-pigs (6.58 vs. 6.50; p < 0.0001) as well as for pigs stunned with SP-A compared to pigs stunned with SP-B (6.53 vs. 6.46, p < 0.0001).
Therefore, the investigations show when choosing the key parameters of electrical stunning, the circumstances of slaughtering at abattoir and the genetic background of the pigs slaughtered should be taken into account in order to ensure animal welfare during stunning. Also meat quality parameters as the pH-SM40 can be optimized by adjusting the SP. This means that the key parameters of electrical stunning must be individually adapted to the abattoir and the animals slaughtered there.
The presented results demonstrate the necessity of further studies, to develop individual SP for genetic lines or pig breeds to adapt national and international recommendations for the key parameters of electrical stunning. In addition to the improvement of animal welfare, an adequate electrical stunning is also of great importance to ensure meat quality.
