A comparison of some muscle metabolites in stress susceptible and resistant Landrace gilts after halothane exposure or exercise stress

Abstract

Sixty-six South African Landrace gilts were used in the experiments. At the age of 21 weeks, 47 of the pigs were challenged with halothane exposure. As a result 17 of the pigs died, and were classified stress susceptible (SS), whereas the 30 survivors were classified stress resistant (SR). The other 19 pigs were subjected to treadmill exercise. Four of the exercised pigs died. The pigs that survived the treadmill exercise were later exposed to halothane. The pigs that died as a result of the halothane exposure ( n = 5) or the treadmill exercise ( n = 4), were classified SS ( n = 9) and the survivors as SR ( n = 10). A biopsy of the M. semitendinosus was used for measurement of difference in muscle lactate, ATP, glucose 6-phosphate, phosphocreatine, glucose and glycogen concentrations. The results show that in all pigs exercise resulted in the higher stimulation of glycogenolysis than did halothane exposure. However, SS pigs overall showed a greater stimulation of glycogenolysis and glycolysis and general anaerobic metabolism, compared to SR pigs. Under halothane exposure, glycogenolysis and anaerobic metabolism were stimulated in the SS pigs to a much greater extent than in SR pigs, with significant differences between all the muscle metabolites determined. However, treadmill exercise, although sufficient to cause death in some pigs, resulted only in significantly higher lactate and glucose 6-phosphate concentrations. SR pigs exposed to halothane had significantly higher ATP, phosphocreatine and glycogen concentrations, but a lower glucose concentration than exercised SR pigs, indicating less severe stimulation of glycogenolysis by halothane than exercise. No significant differences were found in the determined muscle metabolites in SS pigs exposed to halothane compared to exercised SS pigs. In conclusion, these differences suggest that different mechanisms of stimulation of metabolism on exposure to halothane and exercise may exist, although both types of stress cause stimulation of glycogenolysis.