Globally, there is increasing demand for safe poultry food products free from antibiotic residues. There is thus a need to develop alternatives to antibiotics with safe nutritional feed derivatives that maximize performance, promote the intestinal immune status, enrich beneficial microbiota, promote health, and reduce the adverse effects of pathogenic infectious microorganisms. With the move away from including antibiotics in poultry diets, botanicals are among the most important alternatives to antibiotics. Some botanicals such as fennel, garlic, oregano, mint, and rosemary have been reported to increase the poultry’s growth rate and/or feed to gain ratio. Botanicals’ role is assumed to be mediated by improved immune responses and/or shifts in the microbial population in the intestine, with the elimination of pathogenic species. In addition, modulation of the gut microbiota resulted in various physiological and immunological responses and promoted beneficial bacterial strains that led to a healthy gut. There is thus a need to understand the relationship between poultry diets supplemented with botanicals and good health of the entire gastrointestinal tract if we intend to use these natural products to promote general health status and production. This current review provides an overview of current knowledge about certain botanicals that improve poultry productivity by modulating intestinal health and reducing the negative impacts of numerous pathogenic bacteria. This review also describes the efficacy, negative effects, and modes of action of some common herbal plants applied in poultry as alternatives to reduce the use of antibiotics.

This study evaluated the effects of Bacillus subtilis, Saccharomyces boulardii, oregano, and calcium montmorillonite on the physical growth, intestinal histomorphology, and blood metabolites in Salmonella-challenged birds during the finisher phase. In this study, a total of 600 chicks (Ross 308) were randomly distributed into the following dietary treatments: basal diet with no treatment; infected with Salmonella; T1, infected + avilamycin; T2, infected + Bacillus subtilis; T3, Saccharomyces boulardii; T4, infected + oregano; T5, infected + calcium montmorillonite. Our results indicated that feed consumption, body weight gain, total body weight, and feed conversion ratio increased significantly (P < 0.01) in T1 and T2. Villus width increased significantly (P < 0.01) in T1 while the total area was significantly (P < 0.01) higher in T1 and T2 among the treatment groups. Blood protein was significantly (P < 0.01) high in T3 and T4; however, the glucose concentration was significantly (P < 0.01) high in T2, T3, and T4. The treatments increased significantly (P< 0.01) in the treatment groups compared to the negative control. Aspirate aminotransferase (AST) was significantly (P < 0.05) low in T3 compared to the positive control. In conclusion, the results indicated that supplementation of Bacillus subtilis and calcium montmorillonite improved the production performance compared to other feed additives in broiler chicks infected with Salmonella during the finisher phase.

The antifungal activity of seven essential oils (eucalyptus, clove, mint, oregano, savory, tea tree, and thyme) was studied on Venturia inaequalis, the fungus responsible for apple scab. The composition of the essential oils was checked by gas chromatography-mass spectrometry. Each essential oil had its main compound. Liquid tests were performed to calculate the IC₅₀ of essential oils as well as their majority compounds. The tests were made on two strains with different sensitivities to tebuconazole: S755, the sensitive strain, and rs552, the strain with reduced sensitivity. Copper sulfate was selected as the reference mineral fungicidal substance. IC₅₀ with confidence intervals were calculated after three independent experiments. The results showed that all essential oils and all major compounds had in vitro antifungal activities. Moreover, it was highlighted that the effectiveness of four essential oils (clove, eucalyptus, mint, and savory) was higher than copper sulfate on both strains. For each strain, the best activity was obtained using clove and eucalyptus essential oils. For clove, the IC₅₀ obtained on the sensitive strain (5.2 mg/L [4.0–6.7 mg/L]) was statistically lower than the IC₅₀ of reduced sensitivity strain (14 mg/L [11.1–17.5 mg/L]). In contrast, for eucalyptus essential oil, the IC₅₀ were not different with respectively 9.4–13.0 and 12.2–17.9 mg/L for S755 and rs552 strains. For mint, origano, savory, tea tree, and thyme, IC₅₀ were always the best on rs552 strain. The majority compounds were not necessarily more efficient than their corresponding oils; only eugenol (for clove) and carvacrol (for oregano and savory) seemed to be more effective on S755 strain. On the other hand, rs552 strain seemed to be more sensitive to essential oils than S755 strain. In overall, it was shown that essential oils have different antifungal activities but do not have the same antifungal activities depending on the fungus strain used.

Varying concentrations of soil Cr(VI) were used in order to explore the tolerance thresholds and phytoremediation potential of Greek oregano (Origanum vulgare), in a pot experiment conducted outdoors. Oregano exhibited a rather exceptional capacity to bioaccumulate Cr in both the aerial part (up to 1200 mg of total Cr kg⁻¹ DM) and the root—reaching 4300 mg kg⁻¹ DM when grown in soil [Cr(VI)] of 150–200 mg kg⁻¹. Plant responses indicated that there was a threshold set at 100 mg Cr(VI) kg⁻¹ in the soil, above which the following results were recorded: (i) a restriction of Cr translocation from below- to above-ground plant part, (ii) a raise of the soil-to-root Cr transfer, and (iii) the Cr(III) evolution from the reduction of Cr(VI) was significantly decelerated in the root and accelerated in the aerial part. Soil [Cr] that surpassed this threshold challenged plant tolerance, resulting in a dose-dependent reduction of growth and antioxidant phenolics pool. Nonetheless, the significant Cr uptake capacity at plant level accounted for the considerably short remediation time (i.e., 29 years at soil [Cr(VI)] of 150 mg kg⁻¹) calculated according to these results. The overall performance of oregano indicated that phytoremediation would be feasible at sites with Cr contamination levels ranging within the above-defined thresholds.

This study provides, for the first time, data regarding levels of toxic metals (Hg, Cd, and Pb) and organochlorine compounds (PCBs and DDTs) in various aromatic herbs as rosemary (Rosmarinus officinalis), sage (Salvia officinalis), laurel (Laurus nobilis), oregano (Origanum vulgare), and spearmint (Mentha viridis) collected in some towns of the Southern Italy with different anthropogenic and population pressure. Metal and organochlorine compound concentrations were determined using atomic absorption spectrophotometer and gas-chromatography mass spectrometer (GC/MS), respectively. Pb emerged as the most abundant element, followed by Cd and Hg, while between organochlorine compounds, PCB concentrations were higher than those of DDTs. The pollutant concentrations were found to vary depending on the different herbs. The highest Pb levels were observed in rosemary (1.66 μg g⁻¹dry weight) and sage (1.41 μg g⁻¹dry weight), this latter showing also the highest Cd concentrations (0.75 μg g⁻¹dry weight). For PCBs, the major concentrations were found in rosemary (2.75 ng g⁻¹dry weight) and oregano (2.39 ng g⁻¹dry weight). The principal component analysis applied in order to evaluate possible similarities and/or differences in the contamination levels among sampling sites indicated differences area-specific contamination.