Isotope ratio mass spectrometry to detect differences in four compartments of Simmental cows fed on C3 and C4 diets

Fatty acids (FAs) can be found in adipose tissues and muscles of bovines. They may derive from the diet only, as for the essential FAs, and/or from de novo endogenous synthesis [1]. The FAs metabolic pathway starts in the rumen with the hydrolysation of dietary complex fats into long chain FAs [2]. Then, the FAs released during this process are converted into saturated ones through biohydrogenation [3]. The FAs reach the liver carried by the blood, whose flow, together with the FAs concentration, influences their supply to this organ [4]. The deposition of the FAs into the animal tissue represents the final step of their metabolism. The aim of this study was to discriminate between two groups (nTOT=13) of cows fed on different diets and to widen the knowledge about the FAs metabolic path in the bovine organism. The first group was fed on a C3 products-based diet (δ 13CC3_BULK_DIET = -32.55‰) while the second one was fed on a C4 products-based one (δ 13CC4_BULK_DIET = -18.74‰). Beside the diet, three compartments of the animals were considered: rumen, liver and meat. The fat extracted from the four matrices was both analysed through EA-IRMS, as a bulk sample, and through GC-CIRMS, after a derivatization process which made it possible to measure the δ 13C of five FAs (C16:0, C18:0, C18:1n-9, C18:2n-6 and C18:3n-3). A good discrimination between C3 and C4 groups was achieved. Moreover, different trend of δ 13C passing from the diet to the loin were found as for C3 and C4 group