Silybum marianum (L.) Gaertn. in Veterinary Medicine: Phytochemical Diversity, Hepatoprotective Mechanisms, Bioavailability, and Species-Specific Applications

Silybum marianum (L.) Gaertn. represents a phytogenic resource of growing interest in veterinary medicine and animal production because of the hepatoprotective, antioxidant, anti-inflammatory, metabolic, and antifibrotic effects attributed to silymarin and its major flavonolignans. This critical narrative review synthesizes literature published between 1 January 2016 and 3 September 2026 on phytochemical variability, biological and hepatoprotective mechanisms, bioavailability, safety, and veterinary applications. A targeted search was conducted in PubMed/MEDLINE, Web of Science Core Collection, and Scopus for relevant peer-reviewed publications. Experimental evidence indicates interconnected effects on redox homeostasis, inflammatory signaling, mitochondrial function, lipid metabolism, and fibrogenesis. The largest body of direct applied evidence derives from poultry studies, whereas fewer studies are available in swine and aquaculture, and evidence in ruminants, equids, and companion animals remains limited. Interpretation across studies is constrained by heterogeneity in plant material, chemotype, extraction procedures, flavonolignan composition, dose expression, and formulation. The low oral bioavailability of silybin has stimulated the development of micellar, phospholipid-based, nanocrystalline, nanoparticulate, and co-crystal delivery systems. Future research should prioritize well-characterized preparations, species-specific pharmacokinetic and dose–response studies, long-term safety assessment, residue evaluation in food-producing animals, and validation under clinically and commercially relevant conditions.