Effect of feeding lambs with a tanniferous shrub (rockrose) and a vegetable oil blend on fatty acid composition of meat lipids.

ABSTRACT

The effects of feeding Cistus ladanifer (Cistus) and a blend of soybean and linseed oil (1 2 vol/vol) on fatty acid (FA) composition of lamb meat lipids and messenger RNA (mRNA) expression of desaturase enzymes was assessed. In total, 54 male lambs were randomly assigned to 18 pens and to nine diets, resulting from the combination of three inclusion levels of Cistus (50 v. 100 v. 200 g/kg of dry matter (DM)) and three inclusion levels of oil (0 v. 40 v. 80 g/kg of DM). The forage-to-concentrate ratio of the diets was 1 1. Longissimus muscle lipids were extracted, fractionated into neutral (NL) and polar lipid (PL) and FA methyl esters obtained and analyzed by GLC. The expression of genes encoding Δ5, Δ6 and Δ9 desaturases (fatty acid desaturase 1 (FADS1), fatty acid desaturase 2 (FADS2) and stearoyl CoA desaturase (SCD)) was determined. Intramuscular fat, NL and PL contents were not affected by oil or Cistus. Oil supplementation reduced (P<0.05) 160, c9-161, 170, c9-171 and c9-181 FA and increased (P<0.05) 182n-6, 183n-3 and the majority of biohydrogenation intermediates in NL. Cistus alone had few effects on FA of NL but interacted with oil (P<0.05) by increasing t10-181,t10,t12-182,t10,c12-182 and t7,c9-182. The t10-/t11-181 ratio increased with both Cistus and oil levels. The c9, t11-182 did not increase (P<0.05) with both oil and Cistus dietary inclusion. Oil reduced c9-161, 170, c9-171,c9-181, 204n-6, 224n-6 and 203n-9 proportions in PL, and increased 182n-6, 183n-3, 203n-3 and of most of the biohydrogenation intermediates. The Cistus had only minor effects on FA composition of PL. Cistus resulted in a reduction (P<0.05) of 205n-3 and 226n-3 in the meat PL. The expression level of SCD mRNA increased (P=0.015) with Cistus level, although a linear relationship with condensed tannins intake (P=0.11) could not be established. FADS1 mRNA expressed levels increased linearly (P=0.019) with condensed tannins intake. In summary, the inclusion of Cistus and oil in 1 1 forage-to-concentrate ratio diets resulted in a large increase in t10-181 and no increase in c9,t11-182 or n-3 long chain poor in polyunsaturated fatty acids in lamb meat.