Hazelnut skins as a new sustainable ingredient for beef cattle diets

Hazelnut skins (HS), by-products of the hazelnut industry classified as waste, are rich in polyphenols, poli-unsaturated fatty acids and fibres. This study aimed at assessing the in vivo effects of HS inclusion in beef cattle diets. Eighty beef bulls were divided in two groups (control and test; 4 replicates per group), following a two-phase dietary plan (fattening - 5 months; finishing - 2 months). Both groups received forage (hay/straw) and feed, with the test feed presenting an 8% HS inclusion. Feeds' chemical composition and total phenolic contents were assessed. Bulls' in vivo growth performances were recorded, and haematological analysis were conducted at trial start and on slaughter day. Test feeds of both phases presented higher values (p < 0.001) of polyphenols than the control ones. No differences were observed in haematological or growth parameters during the fattening phase. In the finishing, the control group exhibited a lower (p < 0.05) feed conversion ratio than the test. However, the potential health benefits linked to the HS' phenolic compounds, along with the re-valorization of an agro-industrial by-product and the resulting reduction in food waste, support the hypothesis that including HS in beef cattle diets may constitute a viable and sustainable strategy for the beef industry.