Thymol as natural antioxidant additive for poultry feed: oxidative stability improvement

Enhancing nutritional and potential antimicrobial properties of poultry feed through encapsulation of metagenome-derived multi-enzymes

BACKGROUND

The encapsulation of metagenome-derived multi-enzymes presents a novel approach to improving poultry feed by enhancing nutrient availability and reducing anti-nutritional factors. By integrating and encapsulated enzymes such as carbohydrate-hydrolyzing enzymes, protease, lipase, and laccase into feed formulations, this method not only improves feed digestibility but also potentially contributes to animal health and productivity through antimicrobial properties.

RESULTS

This study investigates the encapsulation of metagenome-derived enzymes, including carbohydrate-hydrolyzing enzymes, protease, lipase, and laccase, using Arabic and Guar gums as encapsulating agents. The encapsulated multi-enzymes exhibited significant antimicrobial activity, achieving a 92.54% inhibition rate against Escherichia coli at a concentration of 6 U/mL. Fluorescence tracking with FITC-labeled enzymes confirmed efficient encapsulation and distribution, while physical characterization, including moisture content and solubility assessments, along with Atomic Force Microscopy (AFM) imaging, validated successful encapsulation. The encapsulated enzymes also effectively hydrolyzed poultry feed, leading to an increase in phenolic content and antioxidant activity, as confirmed by 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays.

CONCLUSIONS

The encapsulated multi-enzymes improved the overall feed quality by increasing reducing sugars and enhancing physical properties such as solubility and water-holding capacity. The encapsulated multi-enzymes improved the overall feed quality by increasing reducing sugars, antioxidant activity and enhancing physical properties such as solubility and water-holding capacity. Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FTIR) analyses confirmed the enzymatic breakdown of the feed structure. These results suggest that supplementing poultry feed with encapsulated multi-enzymes can enhance its physical, nutritional, and functional properties, leading to improved digestibility and overall feed quality.

Protected biofactors and antioxidants reduce the negative consequences of virus and cold challenge by modulating immunometabolism via changes in the interleukin-6 receptor signaling cascade in the liver

Protected biofactors and antioxidants (PBA), and protected biofactors and antioxidants with protected organic acids and essential oils (PBA+POAEO) have been shown to have benefits in stressed or challenged birds. Here, we describe the immunometabolic changes observed in the liver of Ross 308 broilers during feed supplementation and brief physiological stress. These studied additives contain protected essential oils, organic acids, and vitamins which may have protective effects on the liver. Thus, we aimed to determine the signaling changes induced by these supplements and the resultant immunometabolic effects in the liver. All birds received a 2X dose of live bronchitis vaccine at d 0 and a 48-h cold challenge by reducing the temperature from 30 to 32°C, to 20 to 23°C on d 3 to 5. Control birds were fed a standard diet without supplementation. Liver samples were collected to evaluate the effects of these treatments on cytokine gene expression and protein phosphorylation via kinome peptide array. ANOVA was used for statistical analysis of the gene expression data (significance at a p-value of 0.05), and PIIKA2 was used for statistical evaluation and comparative analysis of the kinome peptide array data. At d 15, the kinome peptide array analysis and gene expression data showed stimulation of the interleukin 6 receptor (IL-6R) signal transduction for host protection via heightened immune response while inducing immune modulation and reducing inflammation in both supplement treated groups. Significant changes were observed via IL-6R signaling in the metabolic profiles of both groups compared to control and no significant differences when compared to each other. In the liver, these 2 feed additives induced immunometabolic changes predominantly via the IL-6 receptor family signaling cascade. Differences between the 2 treated groups were predominantly in the metabolic pathways, centered around the mTOR pathway and the proteins AMPK, mTOR and S6K, with a more anabolic phenotype following the addition of essential oils.

Thymol improves the growth performance of blue foxes by regulating the gut microbiota

Introduction

The drawbacks of using antibiotics as feed additives for blue foxes have gradually become apparent; moreover, thymol has wide-spectrum antimicrobial activity and has the potential to replace antibiotics in various animals. However, there are few reports on the effects of thymol on blue foxes.

Methods

This study aimed to investigate the effects of different concentrations of thymol on the growth performance, apparent nutrient digestibility, serum biochemical indicators, intestinal morphology, and gut microbiota of blue foxes. Twenty-four male blue foxes (120 ± 5 d) of similar weight (6.05 ± 0.16 kg) were randomly divided into 4 groups. 0, 100, 200, and 300 mg/kg thymol were added to the basal diets of groups C, L, M, and H, respectively.

Results

Compared with those in the C group, the addition of 100 mg/kg thymol to the diet significantly increased organic matter (OM) digestibility, crude protein (CP) digestibility, immunoglobulin (Ig) A, IgM, the VH of the duodenum, the CD of the jejunum, the VH of the ileum, and the VH/CD of the ileum (P < 0.05) and strongly significantly increased IgG (P < 0.01). The addition of 200 mg/kg thymol to the diet increased the VH/CD of the duodenum (P < 0.05). The addition of 300 mg/kg thymol to the diet significantly increased the VH and CD of the jejunum (P < 0.05). The addition of 200 mg/kg and 300 mg/kg thymol to the diets increased the final weight (FW) (P < 0.05). Adding 100 mg/kg thymol significantly increased the levels of interleukin-4 (IL-4) and catalase (CAT) compared with those in the other groups (P < 0.05). 16S rRNA gene detection revealed that thymol can change the abundances of Bifidobacterium, Fusobacterium, Allobaculum, Streptococcus, Megasphaera, and Lactobacillus in the gut.

Conclusion

The addition of thymol to diets can increase the abundance of Bifidobacterium, Fusobacterium, and Allobaculum, which may contribute to improving the growth performance of blue foxes.

Oregano Essential Oil in Livestock and Veterinary Medicine

With a growing global concern over food safety and animal welfare issues, the livestock and veterinary industries are undergoing unprecedented changes. These changes have not only brought challenges within each industry, but also brought unprecedented opportunities for development. In this context, the search for natural and safe products that can effectively replace traditional veterinary drugs has become an important research direction in the fields of animal husbandry and veterinary medicine. Oregano essential oil (OEO), as a natural extract, is gradually emerging in the fields of animal husbandry and veterinary medicine with its unique antibacterial, antioxidant, and multiple other biological activities. OEO not only has a wide antibacterial spectrum, effectively fighting against a variety of pathogenic microorganisms, but also, because of its natural properties, helps us to avoid traditional veterinary drugs that may bring drug residues or cause drug resistance problems. This indicates OEO has great application potential in animal disease treatment, animal growth promotion, and animal welfare improvement. At present, the application of OEO in the fields of animal husbandry and veterinary medicine has achieved preliminary results. Studies have shown that adding OEO to animal feed can significantly improve the growth performance and health status of animals and reduce the occurrence of disease. At the same time, pharmacokinetic studies in animals show that the absorption, distribution, metabolism, and excretion processes of OEO in animals shows good bioavailability. In summary, oregano essential oil (OEO), as a substitute for natural veterinary drugs with broad application prospects, is gradually becoming a research hotspot in the field of animal husbandry and veterinary medicine. In the future, we look forward to further tapping the potential of OEO through more research and practice and making greater contributions to the sustainable development of the livestock and veterinary industries.

Curcumin and curcumin nanoparticles counteract the biological and managemental stressors in poultry production: An updated review

Antibiotics have the potential to have both direct and indirect detrimental impacts on animal and human health. For instance, antibiotic residues and pathogenic resistance against the drug are very common in poultry because of antibiotics used in their feed. It is necessary to use natural feed additives as effective alternatives instead of synthetic antibiotics. Curcumin, a polyphenol compound one of the natural compounds from the rhizomes of turmeric (Curcuma spp.) and has been suggested to have several therapeutic benefits in the treatment of human diseases. Curcumin exhibited some positive responses such as growth promoter, antioxidant, antibacterial, antiviral, anticoccidial, anti-stress, and immune modulator activities. Curcumin played a pivotal role in regulating the structure of the intestinal microbiome for health promotion and the treatment of intestinal dysbiosis. It is suggested that curcumin alone or a combination with other feed additives could be a dietary strategy to improve poultry health and productivity.

The impact of curcumin on livestock and poultry animal's performance and management of insect pests

Plant-based natural products are alternative to antibiotics that can be employed as growth promoters in livestock and poultry production and attractive alternatives to synthetic chemical insecticides for insect pest management. Curcumin is a natural polyphenol compound from the rhizomes of turmeric (Curcuma spp.) and has been suggested to have a number of therapeutic benefits in the treatment of human diseases. It is also credited for its nutritional and pesticide properties improving livestock and poultry production performances and controlling insect pests. Recent studies reported that curcumin is an excellent feed additive contributing to poultry and livestock animal growth and disease resistance. Also, they detailed the curcumin's growth-inhibiting and insecticidal activity for reducing agricultural insect pests and insect vector-borne human diseases. This review aims to highlight the role of curcumin in increasing the growth and development of poultry and livestock animals and in controlling insect pests. We also discuss the challenges and knowledge gaps concerning curcumin use and commercialization as a feed additive and insect repellent.

Role of Dietary Methyl Sulfonyl Methane in Poultry

Oxidative stress is defined as an imbalance between pro-oxidants and anti-oxidants within biological systems, leading to tissue damage and compromising the health of afflicted animals. The incorporation of dietary anti-oxidants into chicken diets has been a common practice to improve the performance, health, and welfare of the host by protecting against oxidative stress-induced damage. Methyl sulfonyl methane (MSM), a naturally occurring organosulfur compound found in various plant sources, has demonstrated various beneficial biological properties, including anti-inflammatory and anti-oxidant properties in both in vitro and in vivo studies. MSM has been utilized as a dietary supplement for humans for its anti-oxidant, analgesic, and anti-inflammatory properties. It has also been administered to domestic animals, including cattle, pigs, and chickens, owing to its recognized anti-oxidant effect. This review summarizes the biological and physiological functions of dietary MSM in poultry.

Oregano (Origanum vulgare) Consumption Reduces Oxidative Stress and Markers of Muscle Damage after Combat Readiness Tests in Soldiers

Military activities often involve high-intensity exercise that can disrupt antioxidant capacity. We investigated the effects of oregano supplementation on muscle damage, oxidative stress, and plasma antioxidant markers of soldiers performing the army combat readiness test (ACRT). Twenty-four healthy male soldiers (age: 24 ± 3 years, height: 167 ± 14 cm, mass: 66 ± 3 kg) were randomized into a placebo group (n = 12) or an oregano supplementation group (n = 12). The participants consumed a capsule containing 500 mg Origanum vulgare immediately after completing the ACRT. Blood sampling was taken before exercise, immediately after exercise, and 60 and 120 min after oregano consumption. Plasma levels of creatine kinase (CK), lactate dehydrogenase (LDH), malondialdehyde (MDA), superoxide dismutase (SOD), total antioxidant capacity (TAC), and glutathione peroxidase (GPX) were measured at the four time points. The time × group interactions were found for CK (p < 0.0001, d = 3.64), LDH (p < 0.0001, d = 1.64), MDA (p < 0.0001, d = 9.94), SOD (p < 0.0001, d = 1.88), TAC (p < 0.0001, d = 5.68) and GPX (p < 0.0001, d = 2.38). In all variables, the difference between placebo and oregano groups were significant at 60 (p < 0.0001) and 120 (p < 0.0001) minutes after ACRT test. The main effect of time was also significant for all the variables (p < 0.0001). Our results suggest that oregano supplementation has the potential to reduce muscle damage and increase oxidative capacity following ACRT. Supplementation with oregano may serve as a dietary strategy to increase preparedness and promote recovery in military recruits.

Effects of Surface Treatment with Thymol on the Lipid Oxidation Processes, Fatty Acid Profile and Color of Sliced Salami during Refrigerated Storage

The oxidation of unsaturated fatty acids and the adverse transformation of pigments from meat and spices are the primary causes of chemical degradation in processed meat products. Thymol is found in a variety of plant extracts that have been proven to effectively inhibit or slow down oxidative processes. The objective of our study was to determine whether thymol treatment of the surface of sliced paprika salami could be applied to inhibit lipid oxidation and color change during refrigerated storage. During eight weeks of storage, the malondialdehyde (MDA) levels and the ratios of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), and n6/n3 in thymol-treated salami remained unchanged (p ≥ 0.05), whereas in the controls, the MDA levels increased by approximately twelvefold and the ratio of SFAs in the lipid fraction increased (p < 0.001), while the ratio of PUFAs decreased (p < 0.001). The application of thymol prevented decrease in yellowness (b*) of the slices and reduced decreases in redness (a*) and brightness (chroma).

Effects of Dietary Organic and Inorganic Sulfur on Laying Performance, Egg Quality, Ileal Morphology, and Antioxidant Capacity in Laying Hens

Simple Summary

Oxidative stress caused by environmental and nutritional factors could be detrimental to poultry production. Dietary natural antioxidants could therefore be beneficial in limiting the deleterious effects of oxidative stress in chickens. Methyl sulfonyl methane is a non-toxic natural organosulfur compound with the chemical formula (CH₃)₂SO₂ and is known as methyl sulfone or dimethyl sulfone. Inorganic sulfate (e.g., sodium sulfate) is involved in the metabolism of many tissues and systems, as well as in important detoxication mechanisms. Dietary sulfur in either organic or inorganic forms exhibits beneficial antioxidant properties in various animals in vivo and in vitro. Therefore, our studies have been conducted to evaluate the role of organic and inorganic sulfur in laying hens.

Abstract

The present study was conducted to investigate the comparative effects of organic and inorganic forms of sulfur, methyl sulfonyl methane (MSM) and sodium sulfate (SS), on laying performance, egg quality, ileal morphology, ileal volatile fatty acids, and antioxidant and stress markers in various biological samples in aged laying hens. A total of 144, 73-week-old Lohman Brown-Lite laying hens were randomly assigned to one of three experimental diets: basal diet (CONT), CONT + 0.2% MSM (MSM), and CONT + 0.3% SS (SS). The trial lasted for 12 weeks. MSM and SS diets contained 0.07% of sulfur, either organic or inorganic. Dietary MSM did not affect egg production or feed conversion ratio at 12 weeks compared with the CONT group. Dietary sulfur did not affect egg quality except for the Haugh unit at 4 weeks, which was lowered (p < 0.05) in the SS group. Compared with the CONT group, a higher (p < 0.05) villus height to crypt depth ratio was observed in the SS group. Dietary sulfur did not affect the percentages of short-chain fatty acids in the ileum. Total antioxidant capacity of the liver increased (p < 0.05) in laying hens fed MSM- and SS-added diets compared with the CONT group. The MSM and SS groups were found to have lowered (p < 0.05) malondialdehyde (MDA) concentration in serum samples compared with CONT. Finally, dietary MSM had the lowest (p < 0.05) MDA concentrations in yolk samples. Taken together, our study showed that dietary organic and inorganic sulfur have positive effects on ileal morphology and antioxidant capacity in laying hens. However, SS-mediated inhibition in laying performance needs to be clarified.

Inverse molecular docking reveals a novel function of thymol: Inhibition of fat deposition induced by high-dose glucose in Caenorhabditis elegans

As a natural product isolated from thyme oil in thyme, thymol (2-isopropyl-5-methylphenol) harbors antiviral, antioxidant, and other properties, and thus could be potentially used for the treatment of various diseases. However, the function of thymol has not been comprehensively studied. Here, we applied an inverse molecular docking approach to identify unappreciated functions of thymol. Potential targets of thymol in humans were identified by the server of DRAR-CPI, and targets of interest were then assessed by GO and KEGG pathway analysis. Subsequently, homologous proteins of these targets in Caenorhabditis elegans were identified by Blast tool, and their three-dimensional structures were achieved using Swiss-Model workspace. Interaction between thymol and the targeted proteins in worms was verified using AutoDock 4.0. Analyses of the targets revealed that thymol could be potentially involved in the glycolysis/gluconeogenesis and fatty acid degradation pathways. To verify the activity of thymol on lipid deposition in vivo, the C. elegans model was established. The lipid content of nematodes induced by high-dose glucose was determined by Oil Red O and Nile Red staining, and gene expression was assessed by qRT-PCR. The results showed that thymol might lead to the acceleration of β-oxidation by upregulating cpt-1, aco, fabp, and tph-1, causing the descent of lipid content in nematodes. Our findings indicated that thymol could be potentially used for the treatment of chronic metabolic diseases associated with increased fatty acid deposition.

Curcumin reduces enteric isoprostane 8-iso-PGF2α and prostaglandin GF2α in specific pathogen-free Leghorn chickens challenged with Eimeria maxima

The purpose of this pilot study was to evaluate and determine the concentration of prostaglandin GF2α (PGF2α) and isoprostane 8‐iso‐PGF2α in plasma and intestine of specific pathogen-free (SPF) Leghorn chickens challenged with Eimeria maxima, with or without dietary supplementation of curcumin using solid‐phase microextraction and ultra‐performance liquid chromatography/tandem mass spectrometry. Eighty 1-day-old male SPF chickens were randomly allocated to one of four groups with four replicates (n = 5 chickens/replicate). Groups consisted of: (1) Control (no challenge), (2) Curcumin (no challenge), (3) Eimeria maxima (challenge), and (4) Eimeria maxima (challenge) + curcumin. At day 28 of age, all chickens in the challenge groups were orally gavaged with 40,000 sporulated E. maxima oocysts. No significant differences (P > 0.05) were observed in the groups regardless of the treatment or challenge with E. maxima. Enteric levels of both isoprostane 8‐iso‐PGF2α and PGF2α at 7 days and 9 days post-challenge were significantly increased (P < 0.01) compared to the non-challenge control chickens. Interestingly, the enteric levels of both isoprostane 8‐iso‐PGF2α and PGF2α at 7 days post-challenge were significantly reduced in chickens fed curcumin, compared to control chickens challenge with E. maxima. At 9 days post-challenge, only levels of isoprostane 8‐iso‐PGF2α in the enteric samples were significantly reduced in chickens challenged with E. maxima supplemented with curcumin, compared with E. maxima challenge chickens. No differences of isoprostane 8‐iso‐PGF2α or PGF2α were observed in plasma at both days of evaluation. Similarly, no significant differences were observed between the challenge control or chickens challenge with E. maxima and supplemented with curcumin at both times of evaluation. The results of this pilot study suggests that the antioxidant anti-inflammatory properties of curcumin reduced the oxidative damage and subsequent intestinal mucosal over-production of lipid oxidation products. Further studies to confirm and extend these results in broiler chickens are required.

Evaluation of microbiological, chemical, and sensory properties of cooked probiotic sausages containing different concentrations of astaxanthin, thymol, and nitrite

In this study, the effects of different concentrations of thymol and astaxanthin on control of Clostridium perfringenes and also microbial, chemical, and organoleptic properties of common and probiotic beef cooked sausages containing two levels of nitrite during storage at refrigerated condition during 45 days were evaluated. Based on findings, control group had significantly higher total volatile base nitrogen (TVB-N) than nitrite-, thymol-, and astaxanthin-treated samples. At the end of the storage time in control, thiobarbituric acid reactive substances (TBARS) value reached 1.96 mg/kg, while the values for treated samples remained lower than 1.63 mg/kg. Final count of lactic acid bacteria decreased approximately 1.67-3.79 log CFU/g in treated samples compared with the control group (p < .05). A reduction between 1.46 and 2.46 log CFU/g in C. perfringenes count was recorded for the treated samples in comparison with control group after 45 days of storage.

Application of essential oils as antimicrobial agents against spoilage and pathogenic microorganisms in meat products

Meat and meat products are perishable products that require the use additives to prevent the spoilage by foodborne microorganisms and pathogenic bacteria. Current trends for products without synthetic preservatives have led to the search for new sources of antimicrobial compounds. Essential oils (EOs), which has been used since ancient times, meet these goals since their effectiveness as antimicrobial agents in meat and meat products have been demonstrated. Cinnamon, clove, coriander, oregano, rosemary, sage, thyme, among others, have shown a greater potential to control and inhibit the growth of microorganisms. Although EOs are natural products, their quality must be evaluated before being used, allowing to grant the Generally Recognized as Safe (GRAS) classification. The bioactive compounds (BAC) present in their composition are linked to their activity, being the concentration and the quality of these compounds very important characteristics. Therefore, a single mechanism of action cannot be attributed to them. Extraction technique plays an important role, which has led to improve conventional techniques in favour of green emerging technologies that allow to preserve better target bioactive components, operating at lower temperatures and avoiding as much as possible the use of solvents, with more sustainable processing and reduced energy use and environmental pollution. Once extracted, these compounds display greater inhibition of gram-positive than gram-negative bacteria. Membrane disruption is the main mechanism of action involved. Their intense characteristics and the possible interaction with meat components make that their application combined with other EOs, encapsulated and being part of active film, increase their bioactivity without modifying the quality of the final product.

Immediate and transgenerational effects of thymol supplementation, inactivated Salmonella and chronic heat stress on representative immune variables of Japanese quail

Environmental challenges are integrated in the inmunoneuroendocrine interplay, impacting the immune system of the challenged individuals, and potentially implying transgenerational effects on their offspring. This study addressed whether dietary supplementation with thymol can modulate the immune response of adult Japanese quail when simultaneously exposed to an inoculum of inactivated Salmonella Enteritidis and a chronic heat stress (CHS). We also evaluated whether the experienced situations by adults can affect the immune response of their undisturbed offspring. In the parental generation, supplemented quail exposed to CHS had a higher inflammatory response and similar values of the heterophil/lymphocyte (H/L) ratio than those that were not supplemented. In their offspring, those chicks whose parents were exposed to CHS showed higher inflammatory response and lower antibody production. Regarding the H/L ratio, chicks whose parents were supplemented showed lower H/L ratio values. Dietary supplementation with thymol partially and positively modulated the inflammatory response and avoided H/L ratio alteration in the parental generation exposed to high environmental temperatures, suggesting these adults were better at dealing with the challenge. The lower H/L ratio values in the offspring suggests that chicks are more capable to deal with potential stressful situations associated with conventional breeding conditions.

Cardioprotective effect of thymol against adrenaline-induced myocardial injury in rats

Cardiovascular disease represents a vital global disease burden. This study aims to assess the possible cardioprotective effect of thymol against adrenaline-induced myocardial injury (MI) in rats. Furthermore the effect of thymol on cardiac function biomarkers, electrocardiogram (ECG) alterations, oxidative stress, inflammation, apoptosis and histopathological changes was assessed. MI was induced by adrenaline (2 mg/kg, s.c.) injected as a single dose for 2 consecutive days (24 h apart). Normal and control groups received the vehicle for 21 consecutive days. The other 3 groups were orally administered thymol (15, 30, 60 mg/kg) for 21 consecutive days and on day 22, adrenaline was injected as a single dose for 2 consecutive days. Then ECG examination, biochemical, histopathological, immunohistochemical analyses were carried out. Thymol reversed adrenaline-induced reduction of heart rate, prolongation of RR interval and elevation of ST interval. Thymol pretreatment significantly reduced serum aspartate dehydrogenase (AST), lactate dehydrogenase (LDH), and creatine kinase (CK) levels in MI rats. Oral pretreatment with thymol increased reduced glutathione (GSH), reduced malondialdehyde (MDA), nuclear factor-kappa B (NF-κB), and interleukin-1β (IL-1β) cardiac contents in MI rats. Additionally, thymol administration significantly decreased protein expression of caspase-3, increased Bcl-2 protein expression in cardiac tissue and ameliorated histopathological changes. This study reveals that thymol exerted cardioprotective effect against adrenaline-induced MI in rats evidenced by improving cardiac function, attenuating ECG and histopathological changes which may be partly mediated through its anti-oxidant, anti-inflammatory and anti-apoptotic effect.

Effects of Microencapsulated Blend of Organic Acids and Essential Oils as a Feed Additive on Quality of Chicken Breast Meat

The present study aims to investigate the effect of dietary supplementation based on a blend of microencapsulated organic acids (sorbic and citric) and essential oils (thymol and vanillin) on chicken meat quality. A total of 420 male Ross 308 chicks were randomly assigned to two dietary treatments: the control group was fed with conventional diet (CON), while the other group received the control diet supplemented with 0.5% of a microencapsulated blend of organic acids and essential oils (AVI). In breast meat samples, intramuscular fat content and saturated/polyunsaturated fatty acids ratio were reduced by AVI supplementation (p < 0.05). Moreover, atherogenic (p < 0.01) and thrombogenic (p < 0.05) indices were lower in AVI than CON treatment. AVI raw meat showed a lower density of psychrotrophic bacteria (p < 0.05) at an initial time, and higher loads of enterococci after 4 days of refrigerated storage (p < 0.05). No contamination of Listeria spp., Campylobacter spp., and Clostridium spp. was found. TBARS values of the cooked meat were lower in the AVI treatment compared to CON (p < 0.01). Among colour parameters, a*, b* and C* values increased between 4 and 7 days of storage in AVI cooked meat (p < 0.05). Overall, organic acids and essential oils could improve the quality and shelf-life of poultry meat.

Thymol Inhibits Biofilm Formation, Eliminates Pre-Existing Biofilms, and Enhances Clearance of Methicillin-Resistant Staphylococcus aureus (MRSA) in a Mouse Peritoneal Implant Infection Model

Methicillin-resistant Staphylococcus aureus (MRSA) is a common human pathogen that causes several difficult-to-treat infections, including biofilm-associated infections. The biofilm-forming ability of S. aureus plays a pivotal role in its resistance to most currently available antibiotics, including vancomycin, which is the first-choice drug for treating MRSA infections. In this study, the ability of thymol (a monoterpenoid phenol isolated from plants) to inhibit biofilm formation and to eliminate mature biofilms, was assessed. We found that thymol could inhibit biofilm formation and remove mature biofilms by inhibiting the production of polysaccharide intracellular adhesin (PIA) and the release of extracellular DNA (eDNA). However, cotreatment with thymol and vancomycin was more effective at eliminating MRSA biofilms, in a mouse infection model, than monotherapy with vancomycin. Comparative histopathological analyses revealed that thymol reduced the pathological changes and inflammatory responses in the wounds. Assessments of white blood cell counts and serum TNF-α and IL-6 levels showed reduced inflammation and an increased immune response following treatment with thymol and vancomycin. These results indicate that combinatorial treatment with thymol and vancomycin has the potential to serve as a more effective therapy for MRSA biofilm-associated infections than vancomycin monotherapy.

Impacts of Strain Variation on Response to Heat Stress and Boldo Extract Supplementation to Broiler Chickens

Simple Summary

One of the common approaches to alleviating heat-stress in poultry is nutritional manipulation using herbal extracts or their derivatives to maintain the health, welfare, and performance of birds. The present study investigated the protective effect of boldo leaf extract against the harmful effects of cyclic heat stress in two broiler strains (Arbor Acres; AA and Avian-48; AV). Administration of boldo in drinking water was able to restore growth and health traits to nearly normal values. Generally, AA chicks were better able to withstand heat stress and were also more likely to utilize boldo extract than AV chicks. The use of boldo leaf extract in poultry production can assist in mitigating the effect of heat stress, improving the antioxidant defense system, and increasing productivity and profitability.

Abstract

There is increasing interest in the use of natural antioxidant supplements in poultry diets as protection against the adverse effects of heat stress. The potential protective effect of boldo (Peumus boldus molina) leaf extract, which have antioxidant activity, were investigated against the harmful effects of heat stress in two broiler strains. Arbor Acres (AA) and Avian-48 (AV) chicks were divided into thermoneutral (TN) and heat stress (HS) groups and treated with 1 g boldo leaf extract/4 L drinking water during the heat stress period. HS reduced growth performance in both strains. The phagocytic index, phagocytic activity, and eosinophil and lymphocytes counts were significantly elevated in TN and HS AV birds but not altered in AA birds. Boldo extract treatment partially eliminated the previous negative impacts of heat stress. AA chicks were better able to withstand HS than AV chicks. Serum concentrations of total lipids and cholesterol were reduced in HS birds of both strains. Malondialdehyde, superoxide dismutase, and glutathione peroxidase levels were elevated but restored with the administration of boldo leaf extract in HS birds of both strains. Economic parameters were negatively affected by HS but restored to values close to those of the control group in boldo-treated HS birds. In conclusion, the administration of boldo leaf extract in drinking water was effective in neutralizing the harmful effects of heat stress on growth performance, blood indices, and economic parameters and improved the antioxidant defense system in heat-stressed birds.

Evaluation of Ascorbic Acid or Curcumin Formulated in a Solid Dispersion on Salmonella Enteritidis Infection and Intestinal Integrity in Broiler Chickens

Two experimental models were conducted to evaluate and compare the effect of ascorbic acid (AA) or curcumin formulated in a solid dispersion (SD-CUR) as prophylactic or therapeutic alternatives to prevent or control S. Enteritidis (SE) infection in broiler chickens. In the prophylactic model, dietary administration of AA showed a significant reduction in SE counts in crop compared to the positive control (PC) group (p < 0.05), whereas in cecal tonsils (CT), SD-CUR significantly reduced SE recovery. Superoxide dismutase (SOD) activity was significantly higher in chickens supplemented with AA or SD-CUR, and total intestinal IgA levels were significantly lower in both treatments when compared to the PC group. Serum fluorescein isothiocyanate-dextran (FITC-d) levels were reduced by SD-CUR compared to PC, while AA presented significantly lower total aerobic bacteria. In the therapeutic model, only the dietary administration of AA significantly decreased SE in crop and CT on days 3 and 10 post-challenge. FITC-d levels were significantly lower in both treated groups in comparison to PC, but IgA levels were significantly reduced only by AA. The results suggest that dietary AA and SD-CUR have different modes of action to reduce SE intestinal colonization in two different challenge models in broiler chickens.

Thymol, alpha tocopherol, and ascorbyl palmitate supplementation as growth enhancers for broiler chickens

Consumer concern on the quality of products and animal welfare has greatly increased during the past decades. Dietary synthetic antibiotic products used as growth promoters have been restricted or banned in many countries. Edible plants, essential oils, or their main components were suggested as natural feed supplements to improve growth, products' quality, and welfare-related parameters. Thymol (THY), a main component of oregano essential oil, has been proved as an effective antimicrobial and antioxidant compound. Tocopherol (TOC) evidenced antioxidant activity with potential as a growth promoter and a synergic antioxidant activity between TOC and ascorbyl palmitate (AP) has also been reported. Herein, we evaluated whether broiler diet supplementation with THY, and THY with a formulation mix containing TOC and AP (1:0.5:0.5, respectively) have potential as growth enhancers under commercial conditions. Potential protective effects against foot pad dermatitis and hock burns were also evaluated. Newly hatched male broiler chicks with similar body weight (BW) were randomly assigned to 1 of 7 groups (4 replicates each) as follows: Basal (no feed supplements added), Promotor (Basal + 6.26 μmol flavomycin/kg feed), BHT (Basal + 1.33 mmol of buthylated hidroxytoluene (BHT)/kg feed), Prom-BHT (Basal + 6.26 μmol flavomycin/kg feed + 1.33 mmol of BHT/kg feed), TOC-AP (Basal + 0.67 mmoles of TOC + 0.67 mmoles of AP/kg feed), THY (Basal + 1.33 mmoles of THY/kg feed), and THY-TOC-AP (Basal + 0.67 mmoles of THY + 0.67 mmoles of a mix 1:1 of TOC-AP). Along 7 wk, BW, feed intake, and feed conversion ratio were evaluated. Skin injuries were assessed at 35 d of age. At the end of the study (42 d), compared to Basal group, similarly enhanced final BW were observed in all groups but TOC-AP. No main differences between groups were detected in feed intake, feed conversion ratio, or skin injuries. Findings suggest that THY itself or in combination with TOC-AP may have value as a natural growth enhancer alternative for broilers.

Blood-brain barrier breakdown, memory impairment and neurotoxicity caused in mice submitted to orally treatment with thymol

Several evidences have related the biochemical and pharmacological properties of thymol, but the possible neurotoxic effects of this compound remain unknown and not evaluated. Thus, the purpose of this study was to evaluate whether intake of thymol in different doses (10, 20 and 40 mg/kg) induce neurotoxicity and behavioral alterations using mice as experimental model, as well as the involvement of blood-brain barrier (BBB) and brain neurotransmitters in these alterations. Thymol (20 and 40 mg/kg) significantly decrease latency time to inhibitory avoidance task when compared to control group, indicating a memory loss after 30 days of oral treatment. Also, thymol (20 and 40 mg/kg) induced a significant increase on BBB permeability to Evan's blue dye when compared to control group, which is an indicative of BBB breakdown. Moreover, a significant increase of brain acetylcholinesterase (AChE) was observed in mice treated with 40 mg/kg of thymol, while the activity of sodium-potassium pump (Na⁺, K⁺-ATPase) was inhibited in mice treated with 20 and 40 mg/kg thymol when compared to control group. Finally, mice that received 20 and 40 mg/kg thymol showed a significant increase on cerebral reactive oxygen species (ROS) levels and cerebral xanthine oxidase (XO) activity compared to control group. Based on these evidences, the rupture of BBB can be considered an important pathway linked in thymol-induced memory loss. Also, the augmentation of brain ROS levels elicited by increase on XO activity may be a via involved in the damage to BBB, and an oxidative pathway that impairs the activity of brain neurotransmitters, as AChE and Na⁺, K⁺-ATPase. In summary, the dose of 10 mg/kg thymol can be safe and without neurotoxic effects in a period of 30 days of intake.

Thymol Induces Conidial Apoptosis in Aspergillus flavus via Stimulating K+ Eruption

Aspergillus flavus is a notorious foodborne fungus, posing a significant risk to humans in the form of hepatocellular carcinoma or aspergillosis. Thymol, as a food preservative, could efficiently kill conidia of A. flavus. However, the underlying mechanisms by which thymol kills A. flavus are not completely understood. With specific fluorescent dyes, we detected several apoptotic hallmarks, including chromatin condensation, phosphatidylserine externalization, DNA damage, mitochondrial depolarization, and caspase 9 activation in conidia exposed to 200 μg/mL of thymol, indicating that thymol induced a caspase-dependent conidial apoptosis in A. flavus. Chemical-protein interactome (CPI) and autodock analyses showed that KCNAB, homologue to the β-subunit of the voltage-gated potassium channel (Kv) and aldo-keto reductase, was the potential target of thymol. Following studies demonstrated that thymol could activate the aldo-keto reductase activity of KCNAB in vitro and stimulate a transient K⁺ efflux in conidia, as determined using a Port-a-Patch. Blocking K⁺ eruption by 4-aminopyridine (a universal inhibitor of Kv) could significantly alleviate thymol-mediated conidial apoptosis, indicating that activation of Kv was responsible for the apoptosis. Taken together, our results revealed a K⁺ efflux-mediated apoptotic pathway in A. flavus, which greatly contributed to the development of an alternative strategy to control this pathogen.

Purinergic system as a potential target for inflammation and toxicity induced by thymol in immune cells and tissues

Thymol is a phytochemical component present in many plants used as food additive in order to promote animal growth due to its several biological properties. However, possible side effects of thymol remain poorly known limited to few reports. In this sense, we evaluated the enzymes of the purinergic signaling such as, ectonucleoside triphosphate diphosphohydrolase (NTPDase), 5'-nucleotidase and adenosine deaminase (ADA), that play an important role on toxicity induced by excessive adenosine triphosphate (ATP) content in the extracellular environment. Thus, the aim of this study was to evaluate whether purinergic signaling could be considered a potential target of thymol-induced inflammation, and the toxicity in tissues and immune cells of mice after thymol administration. NTPDase activity (ATP as substrate) in serum, spleen, and splenic lymphocytes was lower after 30 days of oral treatment at doses of 10, 20, and 40 mg/kg of thymol, while ADA activity was stimulated at 20 and 40 mg/kg. No differences were observed between groups regarding NTPDase (ADP as substrate) and 5'-nucleotidase activities in all evaluated tissues. Based on these evidences, adenine nucleotide hydrolysis is modified in serum, spleen, and splenic lymphocytes of mice treated with thymol, contributing to inflammation and toxicity by a reduction on ATP hydrolyses and its possible accumulation in the extracellular medium and increased Ado desamination and its possible reduction in the extracellular environment, leading to a self-sustained pro-inflammatory deleterious cycle. In summary, all tested thymol concentrations induced inflammation and toxicity in tissues and immune cells of treated mice.

Preventive and Therapeutic Effects of Thymol in a Lipopolysaccharide-Induced Acute Lung Injury Mice Model

Acute lung injury (ALI) is a life-threatening syndrome which causes a high mortality rate worldwide. In traditional medicine, lots of aromatic plants-such as some Thymus species-are used for treatment of various lung diseases including pertussis, bronchitis, and asthma. Thymol, one of the primary active constituent derived from Thymus vulgaris (thyme), has been reported to exhibit potent anti-microbial, anti-oxidant, and anti-inflammatory activities in vivo and in vitro. The present study aims to investigate the protective effects of thymol in lipopolysaccharide (LPS)-induced lung injury mice model. In LPS-challenged mice, treatment with thymol (100 mg/kg) before or after LPS challenge significantly improved pathological changes in lung tissues. Thymol also inhibited the LPS-induced inflammatory cells influx, TNF-α and IL-6 releases, and protein concentration in bronchoalveolar lavage fluid (BALF). Additionally, thymol markedly inhibited LPS-induced elevation of MDA and MPO levels, as well as reduction of SOD activity. Further study demonstrated that thymol effectively inhibited the NF-κB activation in the lung. Taken together, these results suggested that thymol might be useful in the therapy of acute lung injury.