The effect of stress during lairage and stunning on muscle metabolism and drip loss in Danish pork

The effect on meat quality of a low stress handling system (LSS) compared with a traditional handling system (TS) was investigated in Duroc×(Landrace×Yorkshire; n=117) and (Hampshire×Duroc)×(Landrace×Yorkshire) pigs (n=110) under commercial conditions. In the low-stress handling system the pigs were kept in groups of 15 during lairage and movement up to the stunner. Before the stunner the groups were divided into three groups of five pigs for the CO2-stunning in a specially designed set-up. The pH and temperature were determined in m. longissimus dorsi (LD) and m. biceps femoris (BF) at various times post mortem. Immediately after exsanguination a biopsy was taken from the LD and analysed for the concentration of glycogen, lactate and creatine phosphate. The day after slaughter the pH was determined in the LD, BF, m. semimembranosus (SM) and m. semispinalis capitis (SC). The temperature was determined in the LD and BF, the internal reflectance was determined in the LD, SM and BF, the colour was determined in LD, the drip loss was determined in LD and BF, and the amount of blood splashing/bruising was evaluated in LD. There was a tendency for a higher concentration of creatine phosphate in the LSS-group (P=0.06). The pH in both the LD and BF on the day of slaughter decreased more slowly from 5 min post mortem to 40 min post mortem in the LSS-group than in the TS-group (P<0.001). From 40 min to 6 h post mortem the rate of the pH decline was similar in the two groups producing the lowest pH-level in the TS group. The day after slaughter the pH was similar in the two groups in the LD and SC, whereas in the BF and SM it was lower in the LSS-group than in the TS-group. The drip loss was lower in the LSS-group in both LD (P<0.01) and BF (P<0.05) whereas the internal reflectance was only different in LD with the lowest value in the LSS-group (P<0.001). The lightness (L*) was higher in the LSS-group (P<0.05). There was no effect of stunning system on the amount of blood splashing/bruishing in the LD. The study showed that by using a low stress stunning system it is possible to decrease drip loss, possibly by increasing the concentration of creatine phosphate and thereby delaying the acceleration of pH fall in muscles after death.