Two studies differing in facility design and season (Exp. 1 & 2) were conducted to determine effects of pre-slaughter management on pork quality by monitoring blood lactate concentration ([LAC]) and rectal temperature TEMP throughout the marketing process, from loading at the farm to exsanguination, (Exp. 1, n = 80; Exp. 2. n = 144). Blood lactate concentration and TEMP were sampled from each animal at seven points during the marketing process: (1) baseline at the farm, (2) postloading on the truck, (3) pre-unloading after transport, (4) post-unloading at the plant, (5) post-lairage at the plant, (6) post-movement to the stunning area and (7) at exsanguination. Pearson correlations were used to determine relationships between [LAC] and TEMP at the seven sampling points and meat quality. Correlations were also used to relate the changes in [LAC] and TEMP between sampling points to meat quality. Increased [LAC] during loading at the farm resulted in improved meat quality, i.e. increased 24 hr pH (P < 0.002), decreased L* (P < 0.03) and decreased drip loss (P < 0.02) (Exp. 1 & 2). Exsanguination [LAC] was not related to ultimate meat quality (Exp. 1 & 2) even though previous work has demonstrated that higher exsanguination [LAC] is related to lower 45 min pH and increased drip loss. It is hypothesized that these results are due to calm handling in the stunning chute preventing excessive [LAC] production by the skeletal muscles at exsanguination. Also there was a correlation between [LAC] at loading and [LAC] at exsanguination (P<0.002, Exp. 2) suggesting that animals with high [LAC] at loading tended to maintain a high [LAC] at exsanguination. The data suggest that high [LAC] during loading is associated with higher ultimate pH, darker color, and lower drip loss. Therefore, improving pre-slaughter handling at the farm during loading will not necessarily translate to direct improvements in fresh pork quality traits.

Additional Notes from Temple Grandin

The stressful events that were correlated with higher lactate levels at bleeding were rearing, backing up, poking with an electric prod, jamming, and squealing. This data clearly shows that specific aversive handling events were corrolated with increased lactate. Lactate was measured with an easy to use device that is used for testing lactate in atheletes. It is Lactate Scout from EKF Diagnostic GmbH, Magdeburg, Germany. This device could be used to measure the quality of preslaughter handling in pigs. The plant where we did our study had very good handling. The average lactate level for all the pigs at bleeding was only 7.4 mM. Other studies had higher lactate levels that averaged 9 mM in one study and 32 mM in another. High lactate levels at bleeding are correlated to poorer pork quality and greater drip loss.

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