The effect of pre‐treatment of pigs with curare on the post‐mortem rate of pH fall and onset of rigor mortis in the musculature

A number of Large White pigs were immobilised before death with curare, and the rate of post‐mortem change in their muscles was compared with that of a group of control pigs. It is shown that the effect of curare is to give very high and constant initial pH, CP and ATP values in the excised LD muscles, and a slow and constant rate of post‐mortem biochemical and physical change, compared with the very variable rates observed in pigs killed by the normal method of stunning and sticking. Pig muscle, curarised in this way, shows the low post‐mortem rate of pH fall, characteristic of the muscles of other species, when no nervous stimuli are allowed to reach the muscles before death; for example, muscle from myanesinised rabbits, and surprisingly enough, from myanesinised Danish Landrace pigs, which otherwise often show extremely high and variable rates. Thus, there is little or no difference between breeds or species in the rate or time course of post‐mortem change, when the animals are immobilised in this way before death. The cause of the extreme variability of rate of fall in pH, observed in pig muscle in ordinary commercial practice, must therefore be sought in the excitement and struggling, produced before and during slaughter by the methods employed, that is to say in the variable intensity of the nervous stimuli reaching the muscles. It has been experimentally shown that brief electrical stimulation of the excised muscles from the curarised pigs produces not only an immediate increase in the rate of pH fall and of biochemical change, but also has a long‐term accelerating effect, lasting two or more hours, so that the overall rate of change in the stimulated muscles is increased to nearly twice that of the unstimulated muscles. This long‐term effect seems to be unique to pig muscle and does not occur in the muscles of rats, rabbits or frogs, which were the muscles of choice in the classical studies of the chemical changes during contraction. The bearing of the stimulation effect on the variability of pH fall in commercial practice, and thus on the potential occurrence of pale and watery meat on the carcass, is discussed in detail.