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

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 C14:0 as rates of endogenous synthesis increase with higher IMF deposition. This can be related to enhanced C12:0 elongation and lower rates of C14:0 desaturation, supported by a preferential desaturation of C18:1 trans-11 and C18:0 compared with C14:0 and C16:0 as IMF increased. The greatest normalized increase after C14:0 was anteisoC17:0 followed by other branched chain FAs and then trans-MUFA and C18:2 cis-9,trans-11. Finally, C22:6 and C22:5 showed higher relative increase than C20:5 indicating greater rates of elongation and desaturation past C20:5 at higher levels of fatness.

Automated summary

This study investigated the relationship between long-chain fatty acids and intramuscular fat, revealing that saturated and monounsaturated fatty acids increased while polyunsaturated fatty acids decreased with higher IMF content. Furthermore, it was found that rates of endogenous synthesis for specific fatty acids increased with higher levels of IMF deposition.