TRANSPORT AND OTHER POTENTIAL STRESS FACTORS AT SLAUGHTER: EFFECTS OF GENETIC AND REARING BACKGROUND. Studies on pigs

Introduction The slaughter practice involves several potentially stressful procedures, such as mixing of pigs, transport, manipulation and food restriction. Stress reactions at slaughter may be due to physical (food restriction; fatigue; pain due to slaps, shocks or fights) and psychological discomfort (disruption of the social group; fear, due to novelty and human presence). Behavioural stress reactions involve running or on the contrary immobilisation of the animals, making moving them more difficult. Physiological reactions involve increase in heart rate and secretion of stress hormones such as cortisol and catecholamines (adrenaline and noradrenaline). Meat quality is influenced by behavioural and physiological status of the animals before slaughter. Meat quality depends on speed and amplitude of post-mortem muscle pH decline. Amplitude depends mainly on muscle glycogen reserves, speed on muscle metabolic activity, mainly ATPase activity, at slaughter (4). Physical effort increases muscle metabolism, leading to net glycogen loss. Physical effort and psychological stress increase secretion of hormones that exacerbate effects of muscular activity on muscular glycogen depletion (1,2). The way the pig responds to mixing, transport and slaughter stress in terms of physiology and behaviour, is influenced by its genetic background and earlier experience. Various experiments have been conducted to assess responses of pigs of different background to different stages of the slaughter procedure.