Stable isotope ratios of blood components and muscle to trace dietary changes in lambs

Multielemental stable isotope ratio (SIR) analysis was used in lamb plasma, erythrocytes and muscle to detect the switch from a pasture- to a concentrate-based diet, with the aim of verifying the possibility to trace the change of feeding in animal tissues. During 89 days of experimental feeding, lambs were subjected to four dietary treatments: pasture (P), pasture followed by concentrate in the stall for either 14 days (P-S14) or 37 days (P-S37) or concentrate in the stall (5). Pasture and concentrate diets comprised C-3 plants only and had different values of C-13/C-12, O-18/O-16, H-2/H-1 and S-34/S-32 ratios. Muscle C-13/C-12 and S-34/S-32 and plasma C-13/C-12 and O-18/O-16 ratios in P, P-S14 and P-S37 lambs were significantly different. A multivariate analytical approach revealed that C-13/C-12 and O-18/O-16 ratios in plasma were the most powerful variables for the discrimination among the dietary treatments.