The gastrointestinal tract has the largest surface area of the body and if it is subjected to continuous stress, it will activate the immune system. The intestinal barrier, the immune system, and the microbiota together form a line of defense against infection in order to maintain a healthy balance between the host and the microbiota. Nutritional strategies such as feed additives can be applied to maintain homeostasis in the gastrointestinal tract. When this equilibrium is disrupted, metabolic dysfunctions can occur. Postbiotics—the metabolic and/or structural compounds of microorganisms—can stimulate anti-inflammatory, antioxidant, immunomodulatory, and enzymatic effects, providing a safe alternative to establishing intestinal eubiosis. In addition, postbiotics can be used as an alternative to antibiotics in broiler diets by maintaining productive performance under challenging conditions. This review provides an overview of the postbiotic concept, mechanism of action and production, the evidence for the action in the gastrointestinal tract, and applications in poultry production.

Following restrictions on antibiotic growth promoters in poultry production, there is growing interest in natural feed additives that support health and productivity. Among these, black cumin (Nigella sativa) has emerged as a promising candidate due to its antioxidant, antimicrobial, and immunomodulatory properties. Most studies report that black cumin, in the form of whole seeds, seed meal, or seed oil, improves body weight gain and feed conversion ratio, enhances antioxidant and immune status, and provides additional benefits on lipid profiles, liver enzymes, and cecal microbial balance. This review provides a focused synthesis of recent studies (2014–2025) on black cumin supplementation in broiler chickens, considering its various forms (whole seeds, seed meal, seed oil, and nano-formulations) and production contexts (healthy, heat-stressed, and disease-challenged birds). Specifically, this review compares responses across different forms and doses, evaluates effects on growth performance, immune function, gut health, antioxidant status, liver metabolism, and meat and carcass quality, and highlights inconsistencies among studies. Additionally, it identifies key research gaps to guide future investigations, including optimal dosing, long-term safety, and practical applications in commercial production. Overall, black cumin shows potential as a natural alternative to antibiotics, but further standardized, large-scale studies are needed to confirm its efficacy and feasibility in sustainable poultry farming.

This study evaluated the inclusion of increasing levels of xylanase in reduced-energy diets for commercial laying hens. A total of 280 Lohmann LSL white laying hens were equally allocated one of five dietary treatments, with seven replicates of eight hens each being a positive control: a wheat and soybean meal-based diet (PC, ME 2725 kcal/kg), a negative control diet (NC, PC minus 100 kcal) and three diets with increasing xylanase levels of 50, 100 and 150 g/MT (NC + XM50, NC + XM100 and NC + XM150, respectively). The hens were monitored from 20 to 40 weeks of age to assess productive performance, egg quality and intestinal health, including histomorphometry, permeability and microbiota composition. Xylanase inclusion at 50 and 100 g/MT significantly improved egg production and egg mass, as well as shell strength and thickness, while maintaining feed intake and feed conversion efficiency, while xylanase inclusion at 150 g/MT decreased egg production and egg mass. Additionally, intestinal permeability was significantly reduced, and positive changes were observed in the gut microbiota. Higher doses of xylanase (100 and 150 g/MT) increased bacterial abundance and diversity, with a greater presence of beneficial phyla such as Bacteroidota, which play an important role in gut health. There was also a reduction in Actinobacteriota, indicating a lower presence of potential pathogens. Changes in Campylobacterota, Cyanobacteria and Proteobacteria were observed, especially with the highest xylanase dose. These findings suggest that xylanase can improve laying hen performance and promote intestinal integrity and microbial balance when included in energy-reduced diets, offering a promising strategy to enhance health and productivity in commercial egg production systems.

Mycotoxins are a worldwide hazard to animal feed and capable of deleterious effects on poultry. The present study aimed to evaluate the effects of an anti-mycotoxin feed additive on productive and reproductive parameters of breeder hens and roosters fed diets experimentally contaminated with zearalenone (ZEN). A total of 288 hens and 32 roosters (Cobb 500) were randomly distributed in one of four dietary treatments, with nine hens and a rooster per pen and eight pens per treatment: control (C); C + anti-mycotoxin (AM) additive; C + ZEN; and C + AM + ZEN. The trial lasted from 28 to 65 weeks of age. Egg production, egg quality, fertility, hatchability, and hatch rates of fertile eggs were evaluated, as were sperm morphology and abnormalities, and chick quality. ZEN inclusion did not affect egg production but had harmful effects on albumen, egg quality and weight, eggshell thickness, egg fertility and hatchability, and chick length and quality, compared to C, with this negative effect partially alleviated by AM inclusion. Both AM and ZEN, however, decreased spermatic concentration, without affecting sperm morphology or abnormality. The anti-mycotoxin additive effectively mitigated the deleterious effects of ZEN on reproductive parameters and egg quality indexes when fed to breeder hens.

This study evaluated the effects of increasing dietary inclusion levels of branched-chain volatile fatty acids, also called isoacids (ISO), on the growth performance, carcass traits, intestinal health, and breast muscle metabolomic profile of broiler chickens. A total of 700 one-day-old male Cobb 500 chicks were assigned to five corn–soybean meal-based diets with 10 replicate pens (14 birds/pen) in a completely randomized design: A Positive Control (PC) diet formulated to meet nutritional requirements was supplemented with 0.0, 0.10, 0.20, 0.40, or 0.60% of ISO (supplied as a blend of isobutyrate and 2-methylbutyrate). Data were analyzed using General Linear Models with orthogonal polynomial contrasts, PERMANOVA for microbiome beta diversity and ANOVA with FDR correction for metabolomics. Growth performance was monitored across feeding phases. At day 42, carcass traits, breast meat quality, intestinal permeability, cecal short-chain fatty acids (SCFAs), and cecal and ileal microbiota were assessed, alongside liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) metabolomics of the Pectoralis major muscle. Dietary ISO significantly improved average daily weight gain (p < 0.0001) and feed conversion ratio (p < 0.0001) during the first 21 days (early-life), with an optimal inclusion level of 0.40%. While overall carcass and breast yields were unaffected, ISO supplementation significantly and quadratically reduced abdominal fat deposition (p < 0.0001), with an optimal inclusion range between 0.10% and 0.40%. ISO did not compromise intestinal permeability or alter microbial alpha diversity, but it significantly restructured the cecal microbiota (beta diversity; Bray–Curtis p = 0.0213) and linearly increased cecal isobutyric acid accumulation in the cecal content (p = 0.0443). Breast muscle metabolomics revealed a dose-dependent, nonlinear response; the 0.40% inclusion level maximized the relative abundance of galactolipids, whereas the highest dose (0.60% ISO) upregulated sphingomyelins, lysophospholipids, and acylcarnitines. In conclusion, a specific dietary ISO supplementation dose of 0.4% serves as an effective nutritional strategy to boost early feed efficiency and reduce abdominal adiposity. Doses exceeding this optimal level, such as 0.60%, offer no further productive benefits and may trigger cellular stress.