PLASMA AND MUSCLE CORTISOL MEASUREMENTS AS INDICATORS OF MEAT QUALITYAND STRESS IN PIGS

Post-slaughter blood samples and muscle samples were collected from pi gs slaughtered at the completion of a live-animal performance trial. T here were two lines of pigs in which the halothane allele (n) was segr egating. The lines were a lean line selected for rapid lean growth and an unselected fat line. There were homozygous normal (NN), homozygous halothane positive (nn) and heterozygous (Nn) genotypes in both lines . Cortisol was measured in the plasma of the blood samples and in musc le juice obtained by high-speed centrifugation. Meat quality was asses sed using pH, colour, fibre-optic probe, drip loss and cure yield meas urements. Plasma cortisol concentrations in the fat line were signific antly (P < 0.05) greater than those in the lean line but concentration s did not differ significantly for the three halothane genotypes. Carc asses classified as dark, firm and dry (DFD) had significantly (P < 0. 05) greater muscle cortisol concentrations than those classified as no rmal. Plasma and muscle cortisol concentrations of carcasses classifie d as pale, soft and exudative (PSE) did not differ significantly from those classified as normal.Correlations between muscle cortisol and me at quality attributes were generally highly significant (r = 0.31 to r = 0.51, P < 0.001) There was a highly significant correlation (r = 0. 73, P < 0.0001) between plasma and muscle cortisol concentrations.