Stable isotopes to discriminate lambs fed herbage or concentrate both obtained from C3 plants

This study was aimed at determining whether isotopic ratio mass spectrometry (IRMS) enables us to discriminate between lambs fed herbage or concentrate, both obtained from C3 plants, and those fed a concentrate obtained from C4 plants. Thirty‐four Comisana male lambs (age 45 days) were assigned to three feeding treatments. Fourteen lambs were fed vetch (Vicia sativa) ad libitum. Another fourteen lambs received a barley‐based concentrate. The remaining six lambs were fed a maize‐based concentrate. After 60 days of experimental treatment the animals were slaughtered and the wool, perirenal fat and muscle longissimus dorsi were sampled. The δ13C and δ15N values of the muscle, wool and feed were measured by continuous flow elemental analysis (CF‐EA)‐IRMS. The δ13C of the fat was determined likewise. The isotopic composition of the tissues reflected that of the three diets. For the lambs which were fed herbage the muscle δ13C values were higher (P