Physiological Response of Pigs to Treadmill Exercise Used as a Standardised Stress

Abstract

To investigate physiological reactions in slaughter pigs following stress, as for example in transportation to the slaughter plant, groups of animals were exercised on a treadmill for 5 min each at a speed of 1 m/sec. One animal in each of 6 groups was cannulated and at fixed time intervals thereafter for a total period of 5 h blood samples were taken from the cannulated pig. At each of these sampling points, another pig of the group was slaughtered. Samples of exsanguinated blood were taken as well as muscle samples and analysed.

The results indicate significant effects of treadmill treatment on the acid-base status, LDH activity, cortisol concentration and Lactate in blood. During the recovery period most of the parameters returned to the original level within 60–120 min with the exception of LDH.

Changes mentioned above due to stress were similar in catheterised and in slaughtered pigs. In the latter, however, the reactions were more pronounced.

Meat quality and substrates in the muscle were not affected significantly by the treatment, but there were tendencies apparent shortly after stress towards quality deficiencies. In the liver, however, glucose and glycogen were decreased and did not recover within the experimental period of 5 h. Despite the fact that many of the experimental animals were exhausted after treadmill treatment, the glycogen content in the muscle remained unchanged and the exhaustion must have been due to excitement rather than to physical stress.

It can be concluded that pigs should not be slaughtered directly after arrival at the slaughter plant, but should be rested for at least 1–2 h, if they are stressed only by transport. In case of real physical exhaustion associated with glycogen depletion, even more time should be allowed for recovery.