MUSCLE-FIBER CHARACTERISTICS AND METABOLIC RESPONSE AT SLAUGHTER IN PIGS OF DIFFERENT HALOTHANE GENOTYPES AND THEIR RELATION TO MEAT QUALITY

Muscle samples for histochemical and biochemical analyses were taken immediately at slaughter from M. longissimus dorsi of pigs with different halothane genotypes (NN and nn). Fiber type composition was similar between groups but the nn-genotype had larger mean fiber areas and lower capillary density than the NN-genotype. At exsanguination the nn-genotype had lower muscle pH (pH(e)), higher lactate and ammonia and lower glycogen and phosphagen (ATP and CP) concentrations and twice as many glycogen-depleted type IIA and IIB fibres as compared with the NN-genotype. Muscle pH(e) was correlated positively to capillary density, glycogen and phosphagen concentrations and negatively to mean fibre area, ammonia and lactate concentrations. Ammonia concentrations were correlated negatively to ATP concentrations and positively to the percentage of glycogen-depleted IIB fibres. The highest reflectance and drip loss values were seen in the nn-genotype. The reflectance values were correlated positively to the percentage of glycogen-depleted type IIB fibres in muscle and the values for drip loss were correlated negatively to pH(e). These data show that fibre size and capillary density in muscle seem to be important factors that influence the metabolic response at slaughter and thus meat quality.