ISSUE FOCUS FEED & ADDITIVE MAGAZINE February 2026 69 tion of BSH-producing bacteria enhances energy extraction and growth (Lin, 2014; Bourgin et al., 2021). Recent research by Zhan et al. (2025) using single-molecule real-time 16S rRNA sequencing demonstrated that therapeutic antibiotic doses (lincomycin, gentamicin, florfenicol, benzylpenicillin, ceftiofur, enrofloxacin) significantly altered chicken gut microbiota composition, with Pseudomonadota and Bacillota becoming dominant phyla after exposure. Different antibiotics produced distinct temporal effects on microbial diversity and community structure. Phytomolecules exert targeted antimicrobial effects while promoting beneficial bacteria. Dietary supplementation with 800 mg/kg Capsicum extract in Japanese quails reduced cecal counts of pathogenic bacteria (Salmonella spp., E. coli, coliforms) while modulating Lactobacilli populations (Reda et al., 2020). In pigs, 80 mg/kg natural capsicum extract increased cecal propionic acid and total volatile fatty acid concentrations, with increased butyric acid in the colon – indicating enhanced fermentation by beneficial bacteria (Long et al., 2021). Capsicum and Curcuma oleoresins altered intestinal microbiota composition in commercial broilers challenged with necrotic enteritis, reducing disease severity through microbiome modulation (Kim et al., 2015). Capsaicin demonstrates selective antimicrobial activity, inhibiting pathogenic Gram-negative bacteria while favoring development of certain Gram-positive bacteria. The antibacterial mechanism involves induction of osmotic stress and membrane structure damage (Adaszek et al., 2019; Rosca et al., 2020). 4. Intestinal barrier function and gut health AGPs have been associated with improved intestinal morphology, including increased villus height and reduced crypt depth, which enhance absorptive capacity (Gaskins et al., 2002). Phytomolecules produce similar or superior effects. Capsicum extract (80 mg/kg) in pigs increased ileal villus height and upregulated MUC-2 gene expression, indicating enhanced gut barrier function and integrity. The improved barrier function correlated with reduced diarrhea incidence (Liu et al., 2013; Long et al., 2021). Allium hookeri extract increased expression of tight junction proteins (claudins, occludins, ZO-1) in LPS-challenged broiler chickens, demonstrating direct enhancement of barrier integrity (Lee et al., 2017). 5. Oxidative stress mitigation Oxidative stress impairs growth by damaging cellular components and triggering inflammatory responses. AGPs reduce oxidative stress indirectly through anti-inflammatory effects and microbiota modulation (Bortoluzzi et al., 2021). Phytomolecules possess direct antioxidant properties. Capsicum extract (50 mg/kg) in heat-stressed quails reduced serum and ovarian malondialdehyde (MDA) while increasing superoxide dismutase (SOD) and catalase (CAT) activities. Ovarian transcription factors showed decreased NF-κB and increased Nrf2 and HO-1 expression (Sahin et al., 2016). A mixture of herbal extracts including pepper reduced thiobarbituric acid reactive substances and MDA in broiler liver and muscle, while increasing glutathione peroxidase (GSH-Px) activity and improving antioxidant enzyme expression (Saleh et al., 2018). Capsicum extract (80 mg/kg) in pigs increased total antioxidant capacity, SOD, and CAT while reducing MDA levels, demonstrating robust antioxidant effects (Long et al., 2021). STANDARDIZATION AND CONTROLLED RELEASE: CRITICAL SUCCESS FACTORS A major criticism of phytomolecules has been inconsistent efficacy across studies. However, this variability largely reflects differences in: • Active compound concentrations • Bioavailability and stability • Dosing precision • Product quality and standardization
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