New Zealand Journal of Agricultural Research abstracts
Factors affecting the variation in fatty acid concentrations in lean
beef from grass-fed cattle in New Zealand and the implications for human
health
T. W. Knight
S. Knowles
A. F. Death
AgResearch Grasslands
Private Bag 11 008
Palmerston North, New Zealand
email: terry.knight@agresearch.co.nz
J. West
M. Agnew
C. A. Morris
AgResearch Ruakura
Private Bag 3123
Hamilton, New Zealand
R. W. Purchas
IFNHH
Massey University
Private Bag 11 222
Palmerston North, New Zealand
Abstract Lean beef from grass-fed cattle was analysed
for fatty acid (FA) content to determine the between-animal variation and
the effects of various traits on FA composition, and indices and FA ratios
that have human health implications. In Experiment 1, samples were from three
muscles from five bulls, five cows, and five heifers. In Experiment 2, samples
were from the m. longissimus lumborum of 50 3/4
Jersey 1/4 Limousin and 50 3/4
Limousin 1/4 Jersey cattle, born over
2 years and sired by two bulls. The heifers and steers grazed on similar
pastures until slaughter. In both experiments, after adjusting for differences
in total FA content of the meat, there were large coefficients of variation
(CV) for trans-vaccenic, cis-9 trans-11 conjugated linoleic,
and docosahexaenoic acids and low CV for the saturated (SATFA) and monounsaturated
FA (MUFA), and intermediate CV for other FA. There were significant effects
of muscle and animal types in Experiment 1 and of breed, sire, sex, and year-born
in Experiment 2 on the composition and content of individual and groups of
FA, especially the polyunsaturated FA (PUFA). The n-6:n-3, PUFA:SATFA, and
MUFA:SATFA ratios, and the indices for atherogenicity and thrombogenicity,
traits that have human health implications, were affected by factors in both
experiments, but absolute differences were small. The conclusions were that
the FA composition of lean grass-fed beef could be changed by traditional
means to improve the human health image of beef, but the impact would be
small and progress slow. More progress was likely from selecting for beneficial
FA than against undesirable SATFA.
Keywords beef; fat; fatty acids; animal variation; human
health
A02023 Received 4 April 2002: accepted 27 September 2002; published 30
June 2003
New Zealand Journal of Agricultural Research, 2003, Vol. 46: 83-95
0028-8233/03/4602-0083 $7.00/0 © The Royal Society of New Zealand
2003
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