Traceability of animal feeding diet in the meat and milk of small ruminants

Abstract Supplying the consumers with guarantees concerning the feed given to animals needs reliable methods for characterizing meat and milk. Bodies operating product certification systems also require control tools, to be able to guarantee objectively that specification commitments have been fully met. This paper reviews the current state of knowledge concerning the traceability of animal feeding diets in the meat and milk of small ruminants. It presents the potential tracers and different methods that have been studied, together with recent results. Plant biomarkers such as carotenoids, terpenes and phenolic compounds, animal metabolites such as 2,3-octanedione, skatole, fatty acids and ratios of oxygen, carbon and nitrogen stable isotope, are potential tracers in meat and milk or animal tissues, of animal feeding diets. Terpenes, phenolic compounds and ratios of stable isotope are also potential tracers of the geographical origin of milk and meat. Global approaches, especially near infrared spectroscopy and functional genomics are just emerging and need further experimental evaluation. These techniques already allowed to discriminate among products obtained in contrasting feeding conditions. Intermediate situations, for example, in case of modification of animal's diet, may be less easily recognized and may require the combination of tracing methods. In particular, the persistence of tracers when animals are stall-fed a concentrate-based diet after pasture, and its implications for traceability are discussed. Further directions for research are finally highlightened.