Phenolic Compounds and Derivatives in Ruminant Meat and Milk: A Systematic Review

This review synthesizes evidence on phenolic concentrations and diversity in ruminant meat and milk, considering animal species, management, forage, seasonality, and analytical methods. From 39 studies, 356 distinct phenolics were identified in meat and milk, including several from medicinal and non-staple-forage plants. Goat milk showed the highest concentrations as measured by total phenolic content assays (1390 μg GAE/mL) and targeted mass spectrometry (26.79 μg/mL). Beef had the greatest diversity (164 metabolites), followed by sheep milk (110 metabolites); however, beef is also most studied. Organic/agroecological versus conventional systems, fresh versus preserved forages, and younger versus mature pastures were generally associated with a higher phenolic content. Among forages, red clover supported greater diversity than chicory, lucerne, or white clover, while maize silage yielded a higher phenolic content than ryegrass silage. Ruminants can act as biological mediators linking soils, plants, and human diets, often resulting in upcycling of phenolic-derived metabolites from plants not consumed by humans. Future research should integrate soil, plant, animal, and food sciences to fully reveal this role and its potential significance to human health.