The Welfare of Slaughter Pigs During Transport
The welfare of transported pigs can be compromised both by physical and psychological stresses. The animals' responses can be assessed using records of mortality and trauma, physiological and behavioural observations and, to some degree, by measurements of meat quality since this can
reflect the animals' physiological state at death. These assessments may, therefore, be used as measures of animal welfare. During transport pigs show weight loss, increased circulating concentrations of catecholamines, cortisol and creatine phosphokinase (CPK), and an increase in heart rate
and packed cell volume; sometimes there is evidence of dehydration. Increased levels of dark, firm, dry (DFD)meat after long transport reflect muscle glycogen depletion and possibly indicate some element of fatigue. There is experimental evidence that transport is aversive to pigs, which may
be partially due to the fact that they become travel sick. Mortality in transport has ranged from < 0.1 to > 1.0 per cent in different European countries. Mortality is higher in more stress-susceptible breeds and at higher ambient temperatures. It is increased in pigs fed within 4h of
transport, at higher stocking densities and after longer journeys at ambient temperatures greater than 10°C. Pigs may be fasted long enough before slaughter to prejudice their welfare through hunger. Long fasts may also reduce muscle glycogen levels and cause fatigue. Fighting between
unfamiliar animals which have been mixed during the marketing procedure is also stressful, however, longer transport may actually reduce this problem by allowing animals to get used to one another under conditions in which it is difficult to fight.