Table 1.
Biological effects of essential oils (EOs) in poultry production.
| Essential Oils | Effect | References |
|---|---|---|
| The phytobiotic bioactive substances | Increases the activity of amylase and protease. Affects digestive enzyme development and activity. | (Jang et al., 2007) |
| EOs | Minimizes intestinal diseases caused by unwanted bacteria. Promotes good gut microbiota development. Enhances growth performance. | (Bento et al., 2013) |
| Thymol, anetole, eugenol and carvacrol | Increases feed intake. | (Ertas et al., 2005) |
| Cinnamon, oregano, thyme, and eucalyptus EOs | Balances gut microbiota. | (Ulfah, 2006) |
| Oregano EOs | Increases body weight gain in essential oil supplementation, combined with its antimicrobial activity and stimulation of various digestive enzymes that boost nutrient usage. | (Hernandez et al., 2004) |
| Cinnamon powder | Contains cinnamaldehyde that helps increases feed conversion ratio in broilers. | (Decker and Park, 2010) |
| EOs mixture | 200 ppm greatly increases feed conversion ratio by 6 and 12% compared to the antibiotic and the control groups, respectively. | (Ertas et al., 2005) |
| (Myrtle leaf oil, oregano oil, sage leaf oil, laurel leaf oil, citrus peel oil, and fennel seed oil) | Shows considerable improvement in feed conversion ratio. | (Çabuk et al., 2006) |
| Thyme extract | Increases secretion of digestive enzymes, i.e. amylase and chymotrypsin. Increases absorption rates in the intestine. Enhances feed utilization. | (Wade et al., 2018) |
| EOs consisting of 5 g/ton cinnamaldehyde and 15 g/ton thymol | Decreases the growth of undesirable bacteria and enhances beneficial intestinal microbiota growth. Improves growth performance of broilers. | (Tiihonen et al., 2010) |
| Mixture of EOs from caraway, basil, lemon, laurel, sage, oregano, thyme, and tea | Enhances growth performance. | (Khattak et al., 2014) |
| EOs blend at 300 and 600 g/kg of feed | Enhances growth performance. | (Peng et al., 2016) |
| Carvacol and thymol | Increases SOD activity. | (Hashemipour et al., 2013) |
| Ginger EOs at 150 mg/kg | Increases total SOD activity and decreases malondialdehyde concentrations in the liver, which may be attributed to the presence of many antioxidant compounds such as shogaol, gingerol, zingerone, and diarylheptanoids in ginger root. | (Habibi et al., 2014) |
| Cinnamon bark oil at 300 mg/kg diet | Enhances antioxidant status in broilers as SOD activity was significantly increased in cinnamon bark oil–complemented birds compared to the antibiotic treatment. | (Chowdhury et al., 2018) |
| Lemongrass (Cymbopogon citratus) EOs | Inhibits pathogenic bacteria, such as Salmonella typhimurium, Salmonella enterica, Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Klebsiella pneumoniae, and Candida albicans. | (Fagbemi et al., 2009; Naik et al., 2010; Singh and Ebibeni, 2016; Juniatik et al., 2017) |
| Trans-cinnamaldehyde and eugenol | Decreases Salmonella enteritidis in 20-day-old broiler poultry. | (Kollanoor-Johny et al., 2012a) |
| Curcumin, carvacrol, piperin, thymol, and eugenol | Decreases the colonization and proliferation of Clostridium perfringens in the broilers gastrointestinal tract. | (Mitsch et al., 2004) |
| Oreganum aetheroleum EOs | Improves broiler chickens immunity against Escherichia coli infections. Enhances cell-mediated and humoral immune responses. | (Abd El-Ghany and Ismail, 2014) |
| Oregano and thyme EOs | Reduces the number of a broad range of pathogenic bacteria such as Salmonella strains in the chicken gastrointestinal tract. | (Koščová et al., 2006) |
| Thyme, oregano, rosemary, clove, and cinnamon | Preserves the intestinal wall from damage due to the effects of coccidial multiplication. Promotes growth. | (Hashemi and Davoodi, 2011) |
| Anise, citrus, sage, oregano, and bay leaf | Improves nutrients availability by adjusting the intestinal ecosystem. | (Çabuk et al., 2006) |
| Inclusion of 300 and 600 mg/kg oregano essential oil (Origanum spp.) | Improves the birds’ average daily gain. | (Peng et al., 2016) |
| Trans-cinnamaldehyde at 0.75% and eugenol at 1% as an antimicrobial additive in the feed for 5 d prior to slaughter | Reduces cecal colonization of Salmonella enteritidis by 1.5 log10 CFU/g. | (Kollanoor-Johny et al., 2012b) |
| Trans-cinnamaldehyde | Reduces egg-borne transmission of Salmonella enteritidis in commercial layers. | (Abd El-Hack et al., 2021c) |
| Trans-cinnamaldehyde for 66 d at 1 and 1.5% to 40-wk and 25-wk old layer hens | Reduces Salmonella enteritidis on the egg shell and in the yolk without causing any harmful effect on the growth, egg production, and consumer acceptability of eggs. | (Galiş et al., 2013) |
| Carvacrol and thymol | Decreases Campylobacter colonization, although consistency in the antimicrobial effect across the experiments was a problem. | (Abd El-Hack et al., 2021d) |
| Thymol at 0.25 and 1%, or carvacrol at 1%, or a combination of the molecules at 0.5% | Efficient against Campylobacter colonization in broilers. | (Arsi et al., 2014) |
| Garlic and oregano EOs | Reduces population of Clostridium spp. | (Kirkpinar et al., 2011) |
| Cinnamaldehyde and thymol | Shows selective antibacterial properties and reduces yeast, and mold growth. | (Bento et al., 2013) |
| Cinnamon oil | Induces detrimental changes in Escherichia coli cell wall. | (Rahimi et al., 2011) |
| Ajwain oil (AJO), clove oil (CLO), and cinnamon oil (CNO) (400, 600, 300 mg/kg) of diet, respectively | Decreases the counts of Escherichia coli and Clostridium species in pre-cecal contents. | (Chowdhury et al., 2018) |
| Thymol supplementation | Increases intestine length, and the width and depth of the villi. Improves nutrient absorption. | (Alcicek et al., 2003) |
| Carvacol (5.4%), cinnamaldehyde (2.9%), capsicum oleoresin (2.18%) | Increases villus length and intestinal diameter. | (Awaad et al., 2014) |
| Mentha piperita leaves | Enhances histomorphology structure of mucosa of small intestine of broilers. | (Hamedi et al., 2017) |
| Cinnamon oil at 0.3 mg/g of diet | Improves height of villi in duodenum, jejunum, and ileum. | (Chowdhury et al., 2018) |
| Anise, oregano, and citrus peel | Decreases cholesterol by lower the very-low-density lipoprotein levels and increased total flavonoids. | (Hong et al., 2012) |
| Cinnamon essential oil at 300 mg/kg | Reduces cholesterol level and 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase enzyme post-transcriptionally without changing mRNA levels of the enzyme. | (Qureshi et al., 1996; Chowdhury et al., 2018) |
| Thymol, ionone, and carvacrol | Induces a presumed regulatory nonsterol product. | (Elson, 1996) |
| Garlic | Enriches assembly of gamma interferon, interleukins, tumor necrosis factor alpha. Increases phagocytosis of antigen-presenting cells and macrophages. | (Hanieh et al., 2010) |
| Eucalyptus and peppermint EOs | Shows higher hemagglutinin-inhibition antibody titers against both avian influenza (AI) and Newcastle vaccines as compared to control. Shows specific antibody response against influenza vaccine virus. | (Talazadeh and Mayahi, 2017) |
| Thymol EOs | Shows higher (p<0.05) spleen index than birds of control group. Increases the level of secretory immunoglobulin A (p<0.05) in duodenum and ileum mucosa of finisher group. | (Yang et al., 2018) |
| Allium sativum, Echinacea purpure | Effective against intestinal parasites, including the Eimeria species. | (Zhai et al., 2007) |
| Oregano EOs at 300 mg/kg in experimentally infected (Eimeria tenella) birds | Decreases number of Eimeria tenella oocysts. | (Giannenas et al., 2004) |
| Phenols | Exhibits oocysticidal activity against Eimeria tenella. | (Williams, 1997) |
| Supplementation of a natural blend of EOs (basil, lemon, caraway, oregano, laurel, sage, thyme, and tea) | Increases carcass weight, breast weight, and breast meat. | (Khattak et al., 2014)) |
| Oregano EOs supplementation at 600 mg/kg | Displays high breast muscle percent together with augmented dressing percent, eviscerated rate, and leg muscle percent. | (Peng et al., 2016) |
| Ocimum basilicum EOs | Shows antimicrobial activity against a wide range of Gram-negative and Gram-positive bacteria, yeast, and mold. | (Citarasu, 2010) |
| Sunflower oil nanoemulsion | Shows antibacterial activity against foodborne bacteria such as Listeria monocytogenes, Salmonella typhi, and Staphylococcus aureus. Shows high fungicidal and a sporicidal activity against Rhizopus nigricans, Aspergillus niger, Penicillium species, Bacillus cereus, and Bacillus circulans. | (Joe et al., 2012) |
Abbreviations: AI, avian influenza; CFU, colony forming units; FCR, feed conversion ratio; GIT, gastrointestinal tract; HI, hemagglutinin-inhibition; HMG-CoA, 3-hydroxy-3-methylglutaryl coenzyme A reductase; ND, Newcastle disease; SOD, super oxide dismutase; VLDL, very low-dentistry lipoprotein.