European Journal of Nutrition & Food Safety

Tannins are naturally occurring polyphenolic compounds increasingly recognized for their potential benefits to ruminants. Tannins can be extracted from plants' roots, bark, leaves, and seed husks. Management of plant communities to produce a diverse array of secondary compounds, particularly tannins, is a promising strategy for holistically enhancing agroecosystems on rangelands and benefiting free grazing ruminant animals. Deterioration of rangelands constrains plant diversity, reducing tanniferous forage plants and limiting tannin availability to free-grazing ruminants. Ruminants supplemented with tannin extracts in confined feeding operations have gained several reported benefits. Commercial industries are also expanding to extract and process tannin extracts. The beneficial effects of tannins depend on many factors, including plant species, plant part, tannin type (condensed tannins (CTs) or hydrolyzable tannins (HTs), and dose. Tannin binds with proteins, enhances the diversity and abundance of amino acids in the small intestine, and improves overall protein absorption and utilization. Compiled with other mechanisms, tannins can improve the quality, quantity, shelf life, and consumer preference of meat and milk products. Tannins also possess antimicrobial, anti-parasitic, antioxidant, immunomodulatory, and anti-inflammatory properties. CTs also impact rumen microbial populations, decreasing methane production, improving ruminal microbiota diversity, and lowering ammonia nitrogen production. Therefore, the use of tannin from tannin extracts and tanniferous forage plants presents a promising avenue for enhancing confined and free-grazing ruminant animals' health, productivity, and environmental sustainability.