Effects of vegetation type and breed on n-3 and n-6 fatty acid proportions in heart, lung and brain phospholipids of lambs

Abstract

The known influence of forage composition on fatty acid (FA) profiles in ruminants’ meat and milk may be different for other organs. Therefore, in the present study FA profiles of phospholipids in lung tissue, heart muscle and brain (medulla oblongata) were examined in growing Engadine and Valaisian Blacknose sheep grazing 4 pastures of different botanical composition, whereof three were extensively managed natural mountain swards. An intensively managed lowland pasture represented the control. On each pasture type, 6–7 lambs of each breed (54 in total) grazed for 9 weeks and were subsequently slaughtered. Tissue samples were taken at slaughter, homogenized and analyzed for FA profiles after phospholipid extraction. Response to the diets was tissue specific, with the weakest effects being found in brain tissue. Despite for a strong site effect on linoleic acid (P < 0.001), brain lipids were rather resistant to influences of diet. Proportions of linoleic acid in phospholipids were increased by 15–25%, 35–76%, and 31–37% in heart, lung and brain, respectively, in lambs grazing mountain pastures (P < 0.05). Alpha-linolenic acid was increased in heart (18–33%; P < 0.05) and lung lipids (5–36%; P < 0.05) of lambs from the highland sites. Proportions of n-3 and n-6 FA acids in the organs were not unequivocally associated to the concentrations of bioactive plant constituents. Further, the significance of these associations was limited by confounding between phenolic compounds and other plant constituents within the respective sward samples. Some long-chain PUFA were affected by vegetation type, but effects were less clearly related to the pasture location. Most prominently, the proportion of 22:5n-3 in the heart muscle was higher for lambs from the lowland pasture compared to the mountain site with the highest phenol concentrations. Breed effects were fewer than vegetation influences, but concerned feed-derived (e.g. α-linolenic acid), rumen-derived (e.g. CLA) as well as endogenously synthesized FA (e.g. 16:0). Also for the breed effects a strong tissue specificity was found, with the most and strongest effects in lung tissue. In conclusion, even though the direct applicability of the results is limited to the vegetation types investigated, the study demonstrated that FA profiles in functional tissues of ruminants depend on dietary and genetic factors in a differentiated way. This implies that forage composition matters, not only for efficiency and product quality but also for the composition of functional lipids in organs that may influence endogenous processes and health status of the animal itself.