Histochemical characteristics in relation to meat quality properties in the Longissimus Lumborum of fast and lean growing lines of Large White pigs.

A selection experiment was carried out to study genetic and physiological factors influencing meat quality in lines of Large White pigs selected for lean (L) or fast (F) growth. Second and fourth generation pigs were used to determine effects on fibre type composition, fibre diameters and capillary density in the Longissimus Lumborum (LL). Significant differences in histochemical properties were found in the LL between L- and F-pigs, but only in the 4th generation. L-pigs had significantly less type I and more type IIB myofibres compared to F-pigs in both sexes. In both lines lower type I and higher type IIB percentages were determined in gilts compared with boars. Significant differences in meat quality properties between L- and F-pigs were found in the LL, but only in the 4th generation. The a* values were significantly higher in F- versus L-pigs and in boars versus gilts. L* values were not significantly different between lines. However, L* values were significantly lower in 4th versus 2nd generation pigs and in boars versus gilts. In conclusion, genetic selection on lean versus fast growth induces differences in fibre type composition of the LL. These differences become visible in the 4th generation, when a certain selection effect is achieved. Fibre type composition was influenced by the gender of the animal. Meat quality showed significant differences between lines in meat colour (a* value), but only in the 4th generation. Capillary density and fibre area between L- and F-lines showed minor differences, which could be explained by the differences in weight and age of the pigs of both lines.