A thorough review of phytogenic feed additives in non-ruminant nutrition: production, gut health, and environmental concerns.

The increasing demand for sustainable livestock production has intensified interest in phytogenic feed additives (PFAs) as viable alternatives to conventional growth promoters and antibiotics. Derived from plant-based sources such as herbs, spices, and essential oils, PFAs have demonstrated significant potential to enhance production performance, improve gut health, and mitigate environmental impact in non-ruminant systems. Bioactive compounds such as thymol, carvacrol, menthol, and anethole play a crucial role in modulating gut microbiota, strengthening immune responses, and reducing gastrointestinal disorders. Their antimicrobial and antioxidant properties further support animal health while reducing antibiotic dependence, addressing growing concerns over antimicrobial resistance. Additionally, they contribute to improved nutrient digestibility and feed efficiency, leading to enhanced growth performance. From an environmental perspective, their use is associated with lower greenhouse gas emissions and reduced waste contamination, aligning with sustainability goals in modern livestock systems. PFAs improve feed efficiency, leading to reduced feed waste and lower resource input, which in turn decreases the environmental burden of livestock production. Additionally, their antimicrobial properties may reduce the need for synthetic chemicals in animal health management, further minimizing the release of harmful substances into the environment. Despite these promising benefits, inconsistencies in research findings highlight the need for further studies to determine optimal inclusion levels and clarify their mechanisms of action. Future research should focus on developing standardized formulations, improving bioavailability, and assessing long-term effects on animal health and performance. Additionally, advancements in delivery technologies and synergistic combinations with other feed additives could enhance their efficacy. By synthesizing the latest developments, this review underscores the potential of PFAs as a strategic tool for optimizing non-ruminant productivity, ensuring animal welfare, and promoting environmentally sustainable livestock production.