Traceability of lamb production systems: carotenoids in plasma and adiposetissue

This study was conducted to determine whether carotenoid pigments can act a s biomarkers of grass feeding to trace lamb production systems. Three produ ction systems were compared: G = grazing (72 lambs), S = stall-feeding (26 lambs), and GS = grazing period followed by a stall-feeding period (27 lamb s), Presence of carotenoids in tissues was evaluated by plasma concentratio n and reflectance spectrum of subcutaneous caudal adipose tissue. Plasma ca rotenoid content was measured during the grazing period for G and GS lambs, at the end of the grazing period for GS lambs and at slaughter for G, S an d GS lambs. Reflectance spectrum of adipose tissue was measured at slaughte r for 38 G and 26 S lambs. We collected 135 G and 26 S blood samples. Carot enoids were detected in 97% of the G blood samples, whereas they were not d etected in 93% of the S blood samples. Plasma carotenoid content of all the GS lambs decreased during the stall-feeding period. Mean reflectance spect ra of adipose tissue of G and S lambs differed between 450 and 510 nm, whic h corresponds to light absorption by carotenoids. We performed a mathematic al analysis of the spectrum in order to quantify absorbance in this zone an d to propose an index that can be used in the meat industry to trace animal production systems. This method was less discriminating than plasma carote noid analysis, as there was some overlapping in the frequency distribution of the traceability index for G and S lambs that concerned 19% of the lambs . Sensitivity of the two methods to bias and applicability to cattle are di scussed.