EFFECT OF BREED TYPE AND SEX ON THE FATTY-ACID COMPOSITION OF SUBCUTANEOUS AND INTRAMUSCULAR LIPIDS OF FINISHING STEERS AND HEIFERS

Effects of breed type and sex on the fatty acid composition of subcuta neous neutral lipid and intramuscular neutral and phospholipids of lon gissimus lumborum muscle were investigated using 145 steers and 82 hei fers that consisted of pure Japanese Black and Holstein and crossbreds among Japanese Black, Holstein, Japanese Brown, and Charolais. Steers and heifers were reared on a high plane of nutrition and were fed the same concentrate diet and rice straw. All animals were slaughtered se rially and carcass composition was determined by dissection of the lef t side of the carcass. Breed type and sex differences of fatty acid pe rcentages of carcass Lipids were compared by adjusting the percentages to mean carcass fat percentages. Heifers had higher contents of 18:1 and total monounsaturated fatty acids in subcutaneous and intramuscula r neutral lipids than steers (P < .05). The fatty acid composition of intramuscular phospholipids differed between sexes for 16:0, 20:1, and 20:5, but the differences were small. Breed differences were signific ant (P < .05) in steers for 16:0, 16:1, 18:1, and total saturated and monounsaturated fatty acids in both subcutaneous and intramuscular neu tral Lipids, and iso-16:0, 16:0, and total saturated fatty acids in ph ospholipids, respectively. However, in heifers, fewer fatty acids diff ered (P < .05) among breed types in the neutral lipids. It is suggeste d that the Japanese Black has a genetic predisposition for producing c arcass lipids containing higher concentrations of monounsaturated fatt y acids than Holstein, Japanese Brown, or Charolais.