ISSUE FOCUS 68 FEED & ADDITIVE MAGAZINE February 2026 1. Immunometabolic regulation Phytomolecules demonstrate remarkably similar anti-inflammatory effects to what Niewold (2007) suggested was a primary mechanism of AGPs: non-antibiotic anti-inflammatory activity, reducing the energetic costs of chronic low-grade inflammation. Inflammation diverts nutrients from growth toward immune responses, with cytokine production (particularly IL-1β, IL-6, and TNF-α) suppressing anabolic pathways (Kogut et al., 2018). AGPs appear to selectively inhibit pro-inflammatory cytokine production without completely suppressing immune function. A similar effect can be observed with various types of phytomolecules, which significantly reduced pro-inflammatory and/ or increased anti-inflammatory cytokine expression in animals challenged with several pathogens. The anti-inflammatory mechanism appears to involve inhibition of NF-κB activation and modulation of MAPK signaling pathways (Kim et al., 2010; Long et al., 2021). 2. Mitochondrial hormesis and energy metabolism Fernández Miyakawa et al. (2024, see above) proposed that AGPs exert growth-promoting effects through mitochondrial hormesis – subtherapeutic antibiotic doses induce mild mitochondrial stress, triggering adaptive responses that enhance mitochondrial function, energy metabolism, and cellular resilience. This mechanism, while requiring further validation, explains why different antibiotics with diverse targets produce similar growth outcomes. The mitochondrial stress response involves activation of the IL-6 receptor family signaling cascade, which regulates metabolism, growth, regeneration, and homeostasis in liver and other tissues (Perry et al., 2024). Subtherapeutic antibiotic exposure activates proteins involved in growth and proliferation through IL-6R gp130 subunit signaling, including JAK, STAT, mTOR, and MAPK pathways. Phytomolecules demonstrate similar mitochondrial effects. Perry et al. (2024) showed that increased activity of AMPK, mTOR, PGC-1α, PTEN, HIF, and S6K can also be available via phytomolecule activity, suggesting enhanced anabolic metabolism. Capsicum oleoresin supplementation in broilers increased jejunal lipase and trypsin activity, enhanced ileal amylase activity, improved jejunal morphology, and modulated immune organ development, indicating enhanced digestive efficiency and nutrient utilization (Li et al., 2022). Compounds such as vanillin, thymol, eugenol have been shown to improve glucose and lipid metabolism through TRPV1 activation and mitochondrial function enhancement (Gupta et al., 2022; Zhang et al., 2017). 3. Gut microbiota modulation AGPs selectively reduce specific microbial populations, particularly Lactobacillus species that produce bile salt hydrolase (BSH). Since BSH reduces fat digestibility and thus weight gain, AGP-mediated reducPhoto: Freepik.com
RkJQdWJsaXNoZXIy MTUxNjkxNQ==