Selection for reduced muscle glycolytic potential in Large White pigs.: II.: Correlated responses in meat quality and muscle compositional traits

A selection experiment was conducted over six generations in a purebred French Large White population presumably free of the HAL(n) and RN- alleles. Two lines were taken from the same base population and were contemporarily bred: one control line (C) and one line (S) selected for reduced in vivo glycolytic potential (IVGP) of the longissimus muscle. Throughout the experiment, second-parity animals were slaughtered at 100 kg body weight in order to evaluate the correlated effects of selection on meat quality and muscle compositional traits. Heritability values, genetic correlations with the selection criterion and average genetic trends ptr generation were estimated for all traits. Heritability values for the traits measured on several muscles depended on the muscle. Within muscle heritability. estimates for ultimate PII and lightness L* value were of the same order. For enzyme activities, estimates of heritability were from 0.12 to 0.44 for lactate dehydrogenase (LDH), front 0.22 to 0.44 for citrate synthase (CS) and from 0.06 to 0.26 for the LDR/CS ratio. Heritability values for longissimus muscle compositional traits were of medium range (from 0.33 to 0.59), except for nitrogen content. The heritability estimate for the technological yield of cured-cook ham processing was 0.32 +/- 0.09. Most physiological and chemical characteristics of the longissimus muscle were not significantly affected by selection. No genetic change was found for technological yield, though the genetic correlation of this trait with IVGP was in the medium range (-0.42 +/- 0.12). The S line showed significant genetic trends for longissimus muscle enzyme activities and fibre characteristics, indicating that it had a more glycolytic muscle metabolism than the C line, with a lower proportion of oxido-glycolytic fibres, a higher proportion of glycolytic fibres, a higher LDH/CS ratio and a lower haem pigment content. (C) Inra/Elsevier, Paris.