Three ryanodine receptor 1 gene variants (AW: homozygous stress stable, Nn: heterozygous and nn: homozygous stress susceptible) served as a model for stress susceptibility with 96 pigs in each study originating from 6 breeding lines. Their age varied between 4 and 12 weeks and the body weight between 6 and 20 kg. Pig breeding programs which use only the normal genotype (NN) will need to apply supplementary selection criteria to reach further improvements in the constitution of the animals and finally in the carcass and meat quality. 13C and 3,P nuclear magnetic resonance spectroscopy were applied noninvasively in vivo and in a few pigs also post mortem to study the metabolic processes in the biceps femoris muscle after halothane exposure. In contrast to no visible effects of the halothane challenge test, the heterozygous defective allele carriers showed a reduction in the levels of glycogen (57 />), phosphocreatine (44 %), ATP (10.5 %) and muscle tissue pH (0.28) coupled with an increase in inorganic phosphate (355 %) and body temperature (1.71 °C). Overall, these changes were intermediate compared to the dramatic response in the homozygous nn genotype and to the very slow processes in NN. Results of 'H magnetic resonance imaging provided the evidence that the defective allele carriers are leaner than normal pigs already at approximately 11 kg live weight. However, fatter pigs are not necessarily more stress stable. Keywords: Swine, muscle metabolism, body composition, nuclear magnetic resonance, ryanodine receptor

A. M Scholz, A. D Mitchell, H. Song, P. C Wang

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 25: Lactation; growth and efficiency; meat quality; role of exotic breeds in the tropics; design of village breeding programmes;, , 125–128, 1998
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