Inclusion of Polyphenol-Rich Olive Cake in Beef Cattle Diets: Effects on Meat Quality and Nutritional Traits

This study involved 45 finishing Limousin young bulls (initial BW 350 ± 15 kg; aged 250 ± 20 days) reared under commercial conditions and randomly assigned for 250 days to three dietary treatments: a control diet without olive cake (CTR), and diets including partially destoned dried olive cake at 10% (OC10) or 15% (OC15) of dry matter. The effects of the dietary inclusion of partially destoned dried olive cake (DOC) on the physicochemical properties, intramuscular fatty acid composition, nutritional lipid indices, and antioxidant profile of the <i>Longissimus dorsi</i> muscle were evaluated. Meat pH was measured at 45 min, 24 h, and 7 days of aging. Instrumental color, proximate composition, fatty acid profile, lipid nutritional indices, total phenolic content (TPC), individual polyphenols, and antioxidant capacity were determined. Data were analyzed by ANOVA using PROC GLIMMIX in SAS, with orthogonal contrasts to evaluate linear and quadratic responses to olive cake inclusion. Treatments did not affect post mortem pH, and color differences observed at 24 h were not present after 7 days of aging. Crude protein content was lower in OC-fed groups, while total lipid content tended to increase; sodium chloride concentration was higher in OC15 meat. Olive cake supplementation reduced hypercholesterolemic saturated fatty acids and increased stearic, oleic, and polyunsaturated fatty acids, including α-linolenic acid, EPA, and DPA, improving PUFA/SFA and UFA/SFA ratios and reducing atherogenic and thrombogenic indices. Despite a higher peroxidability index, OC groups showed greater muscle TPC and antioxidant capacity, the presence of detectable hydroxytyrosol and tyrosol suggests a possible contribution of dietary olive phenolics or their metabolites, although the exact mechanisms underlying their appearance in muscle tissue remain to be fully elucidated. Overall, partially destoned DOC can be included up to 15% of the finishing diet to improve beef nutritional and functional quality within sustainable circular systems.