Relationships between intramuscular fat percentage and fatty acid composition in M. longissimus lumborum of pasture-finished lambs in New Zealand.

ABSTRACT

This paper reports relationships between fatty acids (FAs) and intramuscular fat (IMF)% in M. longissimus lumborum samples from 108 pasture-fed ewe lambs. Samples ranged in IMF from 1 to 6%. Relationships between %FA with total IMF% were mainly linear with percentages of saturated and monounsaturated FAs (MUFA), including trans-FAs, increasing and polyunsaturated FAs decreasing as IMF% increased. Normalized FA content data at 5.5% relative to 1.5% IMF, showed the highest relative increase for C140 as rates of endogenous synthesis increase with higher IMF deposition. This can be related to enhanced C120 elongation and lower rates of C140 desaturation, supported by a preferential desaturation of C181 trans-11 and C180 compared with C140 and C160 as IMF increased. The greatest normalized increase after C140 was anteisoC170 followed by other branched chain FAs and then trans-MUFA and C182 cis-9,trans-11. Finally, C226 and C225 showed higher relative increase than C205 indicating greater rates of elongation and desaturation past C205 at higher levels of fatness.