(Updated July 2021)
Handling during the last five to ten minutes before stunning will have a significant effect on lactate in the blood. Previous research has shown that high lactate levels are associated with high stress handling where pigs have been shocked multiple times with electric prods (Hambrecht et al 2004-2005 and Benjamin et al 2001). Careful, quiet handling in the stunning race reduced lactate levels and improved pork quality. Lactate levels on the bleed rail at commercial slaughter plants ranged form 4.4 mM in the plants with the best handling to 31 mM when pigs were handled in a high stress manner (Hemsworth et al 2002, Warnss et all 1994, Hambrecht et al 2004, 2005, Edwards et al 2009).
Research conducted by Lily Edwards and her colleagues at Colorado State University has demonstrated that lactate measurements on the bleed rail could be used to assess the quality of pig handling in the stunning race. They used a lactate meter that was originally developed for atheletes. It works in a similar manner as a diabetic's glucose meter and is very easy to use. It is the Lactate Scout, EKF Diagnostic GmbH made in Magdeburg, Germany. Their study was conducted in a large, commerial slaughter plant that ran at a speed of approximately 600 pigs per hour. The plant had a single file race that led to a V conveyor restrainer with an electric stunner. This plant had really good handling of a high speed line. The plant had a single file race that led to a V conveyor restrner with an electric sunner. This plant had really good handling for a high speed line. The electric prod was only used on pigs that refused to move. The average lactate level was only 7.4 mM. This was also the first study that was able to relate specific stressful handling events to higher lactate levels in individual pigs. Pigs that reared, jammed or backed up during immediate pre-slaughter handling had significantly higher lactate levels. Pigs that squealed when they were poked with an electric prod also had higher lactate levels. The lactate levels in pigs that experienced a stressful handling event had lactate levels that varied form 7.3 MM to 9.0 mM. Since this plant had very good handling, lactate levels remained relatively low. This study clearly shows that lactate could be used as an easy objective measure of handling in the stunning race shortly prior to slaughter. High lactate levels at bleeding are associated with increased drip loss and poorer meat quality.
Edwards, L. N. 2009. Understanding the relationships between swine behavior, physiology, meat quality and management to improve animal welfare and reduce transit losses within the swine industry. Dissertation. Colorado State University, Fort Collins, CO, USA.
Hambrecht, E. J., J. Eissen, D. J. Newman, C. H. M. Smits, L. A. den Hartog, and M. W. A. Verstegen. 2005. Negative effects of stress immediately before slaughter on pork quality are aggravated by suboptimal transport and lairage conditions. J. Anim. Sci. 83: 440-448.
Hambrecht, E. J., J. Eissen, R. I. J. Nooijen, B. J. Ducro, C. H. M. Smits, L. A. den Hartog, and M. W. A Verstegen. 2004. Preslaughter stress and muscle energy largely determine pork quality at two commercial processing plant. J. Anim. Sci. 82: 1401-1409.
Hemsworth, P. H., J. L. Barnett, C. Hofmyer, G. J. Coleman, S. Dowling, and J. Boyce. 2002. The effects of fear of humans and pre-slaughter handling on the meat quality of pigs. Aust. J. Agric. Res. 53: 493-501.
Schaeperkoetter, M., et al. 2021. Impact of group stunning on the behavioral and pysiological paratmeters of pigs and sheep in a small abattoir. Meat Science, 179:108538.