Double-muscling character influences the trans-18:1 and conjugated linoleic acid profiles in concentrate-fed yearling bulls.

Seventy-five yearling bulls of the "Asturiana de los Valles" northern-Spanish beef breed (double-muscled, mh/mh, n=24; heterozygous, mh/+, n=26; normal, +/+, n=25) were produced under intensive conditions and the effects of double-muscling genotype on trans-18:1 and CLA isomer profiles were examined. Total trans-18:1 contents, measured as percentages of total fatty acid methyl esters, were 10.98-15.07% in backfat and 8.64-9.46% in muscle, and the major isomer was 10t-18:1 in all animals. In mh/+ animals, 11t-18:1 was the second most abundant trans isomer in muscle whereas in mh/mh and +/+ animals 11t-18:1 and 13t/14t-18:1 were relatively similar. Total CLA percentages were 0.71-0.85% in backfat and 0.32-0.40% in muscle. The highest total CLA percentage found was in mh/+, intermediate in +/+ and lowest in mh/mh animals (P<0.05). Heterozygous animals had significantly higher percentages of 9c,11t- (P<0.01), 11t,13c- (P<0.01) and 9c,11c-18:2 (P<0.05) and also significantly higher percentages of the sum of 9c,11t-/11t,13c-/11t,13t-18:2. Overall, mh/+ animals produced meat with a slightly better trans and CLA profile (i.e., less 10t-18:1 and more 11t-18:1 and 9c,11t-18:2) than other genotypes, however, further improvements would still be necessary to achieve a profile with a positive health image.