Long-term changes in performance and meat quality of Danish Landrace pigs: a study on a current compared with an unimproved genotype

An experiment was conducted in 1995 in order to examine muscle growth, muscle histochemical properties, muscle metabolism and meat quality of two types of Danish Landrace pigs representing the growth potential of years 1976 and 1995, respectively. Danish Landrace pigs representing 1976 (slow-growing, SG) originated from a breeding station where the population was maintained without being selected for production traits such as daily gain, food conversion ratio and meat content. Pigs representing Danish Landrace of 1995 (fast-growing, FG) were bought from certified Danish pig breeders. The pigs were simultaneously tested for performance from 40 to 95 kg live weight. The daily gain, food conversion ratio and meat content of the carcass were improved proportionately by 0.43, 0.24 and 0.03 in FG pigs compared with SG pigs. In m. longissimus dorsi (LD), the cross-sectional area of muscle fibres was smaller in FG pigs compared with SG pigs indicating increased muscle fibre number. Data further suggest increased satellite cell proliferation in muscles of FG pigs. Serum from FG pigs stimulated the proliferation of C2C12 muscle cells to a greater extent than serum from SG pigs, although the serum level of insulin-like growth factor 1 did not differ between pig types. The effect of serum on protein turn-over of C2C12 myotubes did not depend on pig type. The glycogen concentration in the LD did not differ significantly between pig types, while the activity of citrate synthase, 3-OH-acyl-CoA-dehydrogenase, and lactate dehydrogenase were higher in the LD of SG pigs compared with FG pigs. Pork chop colour of FG pigs was proportionately 0.09 fighter (L star) and 0.13 less red (a star) than pork chops of SG pigs. The total muscle pigment concentration in the LD, m. biceps femoris and m. vastus intermedius was proportionately reduced by 0.17, 0.19 and 0.11, respectively, in FG pigs compared with SG pigs. In the LD, the concentration of myoglobin was proportionately reduced by 0.17 in FG pigs. The chemical composition of the LD differed between pig types such that the water content was higher and protein content lower in LD from FG pigs compared with SG pigs. The pH of the LD measured 45 min and 24 h post mortem, drip loss and thawing loss were similar for both pig types. Meat tenderness of conditioned pork chops of FG pigs was slightly reduced in accordance with a decreased intensity of the 31 kDa peptide band and increased cooking loss. The present study suggests that increased muscle fibre number and rate of muscle DNA deposition (satellite cell proliferation) have contributed to the increased muscle growth as a result of selection for performance in pigs under Danish conditions. However the increase in growth performance was accompanied by deterioration in muscle colour and slightly reduced tenderness.