Pre-slaughter conditions, animal stress and welfare: current status and possible future research

Abstract

The present paper describes the main procedures used to slaughter fowl, pigs, calves and adult cattle, sheep, and farmed fish, starting on the farm and ending with the death of the animal at the abattoir. It reviews the currently known causes of stress, indicated by behavioural and physiological measurements on the animal level, and by post-mortem muscle metabolism. During the pre-slaughter period, psychological stress is due to changes of environment, social disturbances and handling, and physical stress is due to food deprivation, climatic conditions, fatigue, and sometimes pain. The exact causes of stress depend, however, on the characteristics of each species, including the rearing system. For fowl, bird catching and crating, duration and climatic conditions of transport and of lairage and shackling are the main known pre-slaughter stress factors. For pigs, stress is caused by fighting during mixing of pens, loading and unloading conditions, and introduction in the restrainer. Handling and novelty of the situation contribute to the stress reactions. For veal calves and adult cattle, disruption of the social group, handling, loading and sometimes unloading conditions, fatigue, novelty of the situation and for calves mixing with unfamiliar animals are known stress factors. Gathering and yarding of extensively reared lambs and sheep causes stress, particularly when shepherd dogs are used. Subsequent transport may induce fatigue, especially if sheep are commercialised through auctions or markets. In farmed fish, stress is predominantly related to environmental aspects such as temperature, oxygen, cleanliness of the water and, to a certain extent, stocking density and removal of the fish from the water. If transport and lairage conditions are good and their durations not too long, they may allow pigs, calves and adult cattle, sheep, and fish to rest. For certain species, it was shown that genetic origin and earlier experience influence reactions to the slaughter procedure. Stunning techniques used depend on the species. Pigs and fowl are mostly electrically or gas-stunned, while most adult cattle are stunned with a captive bolt pistol. Calves and sheep may be electrically stunned or with a captive bolt pistol. Various stunning methods exist for the different farmed fish species. Potential causes of stress associated with the different stunning procedures are discussed. The paper addresses further consequences for meat quality and possible itineraries for future research. For all species, and most urgently for fish, more knowledge is needed on stunning and killing techniques, including gas-stunning techniques, to protect welfare.

Influence of production system in local and conventional pig breeds on stress indicators at slaughter, muscle and meat traits and pork eating quality

“…Thus, pigs reared in the E system fought more (higher number of pigs involved) and had a higher physical (muscular) activity during the pre-slaughtering period than pigs in the C system. This is probably explained by the differences in transport conditions of the BE pigs compared with the other experimental treatments, which were inherent to production systems (Terlouw et al, 2008). Indeed, according to Barton Gade (2008), outdoor rearing per se did not influence the number of carcasses with unacceptable skin damages or plasma CK levels at slaughter.…”

“…Global energy metabolism was evaluated by determining plasma glucose and lactate levels, which indicate the balance between mobilization and use of energy primarily for muscle activity and the intensity of anaerobic metabolism, respectively (Lebret et al, 2006). The physical activity of pigs was assessed through plasma levels of CK and LDH, which are released into the circulatory system after high muscular activity, and fighting behaviour was estimated by the number of skin lesions (Terlouw et al, 2008).…”

Factors associated with mortality of broilers during transport to slaughterhouse

“…Both DoA and carcass rejection can result from all primary production steps (Lupo et al, 2009). In an integrated 'from farm to fork' approach to food animal production, all these primary production steps should be considered as related to poultry production quality (Terlouw et al, 2008). Estimation of DoA percentage and variation is therefore of great importance in order to evaluate the current situation, set up alert criteria and establish progress targets.…”

Stress reactivity and its relationship to beef quality in Nguni steers supplemented with Acacia karroo leaves

“…Beef cattle experience several physical and/or psychological stressors during pre-slaughter periods (Gregory, 2008;Terlouw et al, 2008). The consequences of these stressors range from weight loss and death to impaired carcass and meat quality (Foury et al, 2005;Nanni Costa, 2009).…”

“…The consequences of these stressors range from weight loss and death to impaired carcass and meat quality (Foury et al, 2005;Nanni Costa, 2009). The magnitude of any negative effect is a function of the type, duration and intensity of the individual stressors, production system and susceptibility of each individual animal to stress (Ferguson and Warner, 2008;Terlouw et al, 2008). The susceptibility of the individual animal to stress is, in particular, influenced by genetics (Ndlovu et al, 2008;Muchenje et al, 2009;O' Neill et al, 2009) and nutrition (Schaefer et al, 2001;Lowe et al, 2002).…”