FATTY-ACID CONTENT AND COMPOSITION OF UK BEEF AND LAMB MUSCLE IN RELATION TO PRODUCTION SYSTEM AND IMPLICATIONS FOR HUMAN-NUTRITION

Although ruminant meats normally have a low ratio of polyunsaturated f atty acids (PUFA) to saturated fatty acids (P:S ratio), the muscle con tains a range of C-20 and C-22 PUFA of both the n-6 and n-3 series of potential significance in human nutrition. However, information on the amounts of these fatty acids in muscle and how they are modified by p roduction system is limited In this study, the content and composition of fatty acids was determined in several muscles from beef steers fed grass (grazed) and bulls fed cereal concentrates. These are the two m ain types of beef production in the UK and Europe. Muscle fatty acids were also determined in lambs fed grass (grazed on pasture). The total fatty acid content of all muscles studied was less than 35 g kg(-1). The percentages in total fatty acids of all n-3 P UFA were higher in m uscles from steers fed grass than from bulls fed concentrates whereas all n-6 PUFA were higher in the latter. The gluteobiceps muscle contai ned the largest amounts of fatty acids including PUFA and the m. longi ssimus dorsi the least amounts of PUFA in beef and lamb, and m. longis simus contained the lowest percentages of PUFA. Arachidonic acid was t he major fatty acid in the C-20 + C-22 PUFA in beef from both producti on systems with twice as much in muscles from bulls fed concentrates. The P:S ratios were higher in the latter animals, range 0.21-0.34 comp ared with 0.08-0.13 in the steers fed grass. However, the nd.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. These effects of production system in rumina nts are larger than previously reported. Lamb muscle P:S ratios resemb led those in grass-fed beef but the n-6:n-3 ratios were lower. The per centage of trans unsaturated 18:1 fatty acids was similar in both catt le production systems but lamb muscles contained twice as much as beef . Although the concentrations of the C-20 and C-22 PUFA are much lower than in fish, maintaining high n-3 levels in ruminant meats through g rass feeding may be advantageous in human nutrition since meat is more widely consumed. (C) 1998 Elsevier Science Ltd. All rights reserved.