Production System and Fatty Acid Content of Beef and Lamb

Background and methodology
Ruminant meats normally have low ratio of polyunsaturated fatty acids (PUFA) to saturated fatty acids, but information on the amounts of these fatty acids in muscles and how they are modified by production system is limited. In this study, the content and composition of fatty acids in several beef muscles from beef fed grass (grazed) and bulls fed cereal concentrates was determined. Muscle fatty acids in lambs fed grass (grazed on pasture) were also determined.

Results of the study showed that the total fatty acid content of all muscles was less than 35 g kg. The percentages in total fatty acids of all n-3 PUFA were higher in muscles from steers fed grass than from bulls fed concentrates, whereas all n-6 PUFA were higher in bulls fed concentrates. The polyunsaturated acid:saturated acids (P:S) ratios were higher in bulls fed concentrates, ranging from 0.21-0.34 compared with 0.08-0.13 in steers fed grass. However, the n-6:n-3 ratio was much less desirable in the bulls; 15.6-20.1 compared with 2.0-2.3 in the steers fed grass. The percentage of trans unsaturated 18:1 fatty acids was similar in both cattle production systems but lamb muscles contained twice as much as beef.

Enser, M., Hallett, K. G., Hewett, B., Fursey, A. J., Wood, J. D., & Harrington, G. (1998). Fatty acid content and composition of UK beef and lamb muscle in relation to production system and implications for human nutrition. Meat Science 49(3):329-341.