BREED DIFFERENCES IN THE FATTY-ACID COMPOSITION OF SUBCUTANEOUS AND INTRAMUSCULAR LIPID OF EARLY AND LATE MATURING, GRAIN-FINISHED CATTLE

Fatty acid composition was measured in lipid extracted from adipose ti ssue and muscle collected at slaughter from 6 groups of crossbred catt le of about 2 years of age, grain-finished in a feedlot. The cattle ra nged in biological type from late to early maturing. They were progeny of the following crosses: Charolais x (Simmental.Hereford), Simmental x (Simmental.Hereford), Charolais x (Jersey.Hereford), Hereford x Her eford, Hereford x (Jersey.Hereford), Jersey x Hereford. The fat conten t of muscle from the leanest late-maturing cross was 5.2% rising to 10 .4% in the fattest early-maturing cross. There was no significant diff erence in the fatty acid composition of subcutaneous fat between the 6 crosses, but there was in the concentration of some of the fatty acid s of intramuscular lipid. The latter was due on one hand to the increa sed deposition of neutral lipid in early-maturing animals and on the o ther to a higher proportion of polyunsaturated fatty acids in membrane phospholipid in late-maturing animals. The proportions of the monouns aturated fatty acids palmitoleic (C16:1) and oleic (C18:1) were higher in the early-maturing JerseyxHereford crosses than in straight-bred H erefords or the other crosses, but only in the C16:1 values was there a significant difference between breeds. There was also a significant difference between breeds in the sum of monounsaturates and the sum of polyunsaturates in intramuscular fat. The Jersey crosses had the high est level of monounsaturates and the lowest level of polyunsaturates. Intramuscular phospholipid was examined in the 2 breeds that were the most divergent in terms of intramuscular fat content, the Charolais x (Simmental.Hereford) and the Jersey x Hereford. The latter had signifi cantly higher C16:1 values and significantly lower C18:2 and polyunsat urate fatty acid values. The experiment demonstrated that breed differ ences occurred in fatty acid composition of muscle total lipid and pho spholipid. The differences are of significance in human health and in identifying maturity breed-types of cattle.