Effects of dietary supplementation with olive cake enriched in polyphenols on growth, rumen fermentation, and metabolic status of finishing Limousine bulls

This study aimed to evaluate the effects of supplementing olive cake (OC) enriched with poly-phenols (EOC) on the performance, inflammometabolic response, and rumen metabolism ofLimousine bulls. Thirty bulls were blocked by body weight (BW) and randomly allocated to twogroups (15 per group): a 0% inclusion group (CTR) and a 13% inclusion group of EOC in theconcentrate (EOC) for 80 days. At 0, 40, and 80 days of treatment, individual BW measurementsand blood samples were collected, while rumen fluid samples were taken after slaughter. TheEOC group exhibited higher levels of rumen propionate and heptanoate, along with lower levelsof acetate, isobutyrate, and isovalerate compared to the CTR group. Additionally, the EOC groupshowed increased blood urea, c-glutamyl transferase, and alkaline phosphatase, while levels offructosamine, albumin, ferric reducing antioxidant power, calcium, and zinc were lower com-pared to the CTR group. Although performance did not differ significantly between the groups,the inclusion of OC in the concentrate may negatively impact feed efficiency, potentially leadingto reduced liver functionality due to the high content of low-degradable NDF and elevated ADFlevels in the enriched OC, along with possibly increased organic peroxides. Nonetheless, rumenfermentation data indicate a positive modulation of rumen metabolism towards volatile fattyacid (VFA) production pathways that reduce hydrogen ion availability for methane production