Effect of pasture and concentrate diets on concentrations of carotenoids, vitamin A and vitamin E in plasma and adipose tissue of lambs

• Retinol and tocopherol were detected in milk from sheep fed on pasture.
• Lutein and β-carotene in plasma are useful to discriminate lambs fed on pasture.
• Products from sheep fed on pasture have higher amounts of retinol and tocopherol.
• Fat retinol, tocopherol, AVI of translated spectra (450–510 nm) used to classify lambs.
• Fat retinol, tocopherol and AVI classified 100% of lambs according to their diet.

The effect of different diets on the content of carotenoids, fat-soluble vitamins (retinol and tocopherol) and color measurements in sheep tissues was assessed, to study the possible links with the livestock production system for both nutrition and traceability. Three groups of animals were considered: 15 lambs fed on pasture (G1), 15 lambs fed on concentrate (G2) and 15 suckling lambs (G3) whose mothers were grass-fed. Lutein and β-carotene appeared only in plasma from grazing lambs, so they appear useful to differentiate lambs fed on pasture. Furthermore, retinol and α-tocopherol content in fat were significantly higher (p < 0.01) in the animals fed on an extensive system (1.48 ± 0.08 and 42.4 ± 1.76 μg/g fat, respectively) than those fed on an intensive one (1.03 ± 0.08 and 34.8 ± 0.23 μg/g fat, respectively). When fat-soluble vitamin (retinol and tocopherol) levels and the absolute value of the integral from the reflectance spectrum, between 450 and 510 nm, from fat samples were used in a discriminant model, 100% of the lambs were correctly classified according to their feeding system (pasture vs. concentrate).