Fatigue of three skeletal muscles in domestic and wild pigs. A comparative study in situ

The semitendinosus, the gastrocnemius and the soleus muscle were stimulated in situ in young, female domestic pigs (Sus scrofa domestica, German Landrace) and in European wild pigs (Sus scrofa scrofa), by supramaximal impulses via the sciatic nerve. Fatigue indices of the whole muscles were registered during a continuous supramaximal stimulation with square wave impulses (0.3 ms) that were given for 10 s with a frequency of 100 Hz. In domestic pigs, fatigue indices of all three muscles were significantly (p less than 0.001) lower than in wild pigs. The extremely rapid fatigue of domestic pig muscles was remarkably different from that measured in wild pigs, comparing either pigs of nearly the same body weight (FI: 22.7/58.6 for the semitendinosus muscle; 28.5/63.7 for the gastrocnemius muscle; 37.7/81.2 for the soleus muscle), or pigs of nearly the same age (FI: 23.1/58.8 for the semitendinosus muscle; 25.9/65.1 for the gastrocnemius muscle; 33.6/81.4 for the soleus muscle). Doses of anaesthetics needed for appropriate general anaesthesia of young wild pigs were two to three times higher than doses used for domestic pigs. Differences in fiber type composition of the muscles, and alterations in signal transmission characteristics at neuromuscular junctions are discussed as to be associated with the extremely low fatigue resistance of the domestic pig muscles.