Influence of caffeine on blood creatine phosphokinase levels in swine.

Eight stress-susceptible and eight normal pigs weighing 35 to 50 kg were studied to determine if caffeine administration would trigger the stress syndrome and affect blood CPK levels. The pigs were littermates of Yorkshire descent. One gram of caffeine (dissolved in 10 ml of saline-sodium benzoate solution) was infused into the pigs through a jugular catheter at a rate of 1.0 ml/min. Blood samples were collected through the catheter before caffeine administration and at specific intervals up to 8 hr after the caffeine administration for the determination of blood creatine phosphokinase levels. The pigs were sacrificed approximately 48 hr after caffeine administration, and M. longissimus pH and reflectance values were obtained 45 min and 24 hr postmortem. Caffeine administration stimulated the development of the signs associated with the porcine stress syndrome in seven of the eight pigs genetically classified as stress-susceptible, and only one control pig exhibited an early sign of the stress syndrome, muscle tremors. Blood CPK levels did not differ significantly between the normal and stress-susceptible groups until visual signs of the stress syndrome were no longer observed (approximately 45 min after caffeine administration). Stress-susceptible pigs had significantly higher blood CPK levels than controls 45 min after the initial caffeine administration. Physical stress received by the pigs during transport and the stress from being held in a new environment resulted in a greater elevation of blood CPK than did the stress administered through the caffeine infusion.