RELATIONSHIPS BETWEEN SUBJECTIVE AND OBJECTIVE ASSESSMENTS OF STRESS AT SLAUGHTER AND MEAT QUALITY IN PIGS

A study was carried out to relate subjective and objective measures Of stress al slaughter and meat quality in pigs. Thirteen slaughter plan ts were visited. The systems used for handling the pigs pre-slaughter and the levels of stress experienced by the animals were subjectively assessed. The sound level immediately before stunning was also measure d. Generally, systems that were rated as being most stressful also pro duced higher levels of sound, probably because of the vocalisations of the pigs. As the size of plant increased, there was a tendency for th e level of stress, and the recorded sound level, to increase. This app eared to be because larger plants operated faster and were more likely to use restraining conveyors supplied by races to handle the animals before stunning. The restraint associated with these seems stressful t o pigs. Five plants were selected for further study. Two had been asse ssed as having handling systems that produced a low level of stress in the pigs, one as having a system producing a mediwn level, and two as having poor systems producing high levels of stress. Blood samples we re collected al exsanguination, and meat quality was assessed. As the level of subjectively assessed stress experienced by the pigs increase d, so did the average blood levels of lactate and creatine phosphokina se (CPK). There was also a progressive increase in the potential incid ence of pale, soft, exudative (PSE) and dark, firm, dry (DFD) meat in the plants using more stressful handling systems. Additionally, there were positive relationships between sound level and lactate and CPK, a nd sound level and indices of poorer meat quality. Cortisol concentrat ions were not different in pigs killed in the different systems and pr obably reflect events earlier in the handling process, such as in tran sport and lairage, rather than the stress experienced immediately befo re stunning. The overall conclusion was that subjective assessments of the stress suffered by pigs correlate well with objective measures an d that higher stress levels are associated with poorer meat quality.