Essential Oils Function as Feed Additives
Dr. Rambabu.D, Associate Professor
Dept. of Poultry Science, College of Veterinary Science, Korutla
PV Narsimha Rao Telangana Veterinary University
Jagtial dist – 505 326. Telangana State.
e-mail: ram_vetdoc@rediffmail.com
Introduction
The aromatic oily liquids known as essential oils (EOs) are taken from various plant parts, including seeds, leaves, twigs, flowers, roots, bark, wood, fruits, and more. They are steam volatile chemicals that have been used for centuries to impart flavour and fragrance to foods and cosmetics because of their potent aroma and bioactivity. The antibacterial, antifungal, and pesticidal capabilities of EOs and its many derivatives have lately been recognised for their use as natural preservatives and additives. The phrase “essential” originates from Paracelsus Von Hohenheim’s thesis of “quinta essentia,” which was put forward in the 16th century. Essential oils are created by plants’ secondary metabolism, and their bioactivity is based on the intricate makeup of their volatile molecules. Additionally, it varies with regard to plant species, harvesting methods, and plant chemotypes, and its effects on animals are influenced by how they are processed, stored, and how well the animals’ gastrointestinal tracts are functioning. More than 17000 plant species belonging to about 60 plant families, including the Alliaceae, Apiaceae, Asteraceae, Lamiaceae, Poaceae, Myrtaceae, and Rutaceae, have been found to possess essential oil properties. These properties play a significant part in protecting the plant from external threats like herbivores, insects, and plant pathogens. Terpenes, terpenoids, phenylpropanes, and phenols are just a few of the different substances found in EOs that give a variety of plants their distinctive fragrant and medicinal qualities. One of the main constituents of essential oils, terpenoids are produced by plants’ glandular tissues, notably glandular trichomes. In a plant cell, two separate chemical chains combine to create the two primary precursors of terpenoids, isopentenyl diphosphate (IPP) and its isomer dimethylallyl diphosphate (DMAPP). Sesquiterpenoids are produced via the cytoplasmic acetate-mevalonate pathway with acetyl-CoA condensation, whereas isoprene, monoterpenes, and diterpenes are produced by the plastidial methylerythritol phosphate (MEP) pathway using pyruvate and glyceraldehyde-3-phosphate. The remaining aromatic components of essential oils, besides terpenoids, are produced through a different shikimate pathway.
Technique for essential oil extraction
Hydro or steam distillation is typically used to extract essential oils from the leaves, seeds, roots, and flowers of fragrant plants. Essential oils from various plant components are also isolated by cold pressing. Some of the more contemporary methods for extracting the volatile portion of plants include supercritical fluid extraction (SCFE), ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), solvent-free microwave extraction (SFME), and microwave hydro diffusion and gravity (MHG).
Essential oils’ antimicrobial activity
Although essential oils are frequently utilised as flavouring and aromatic agents, they also have this property. The pH, bioactive component content, kind, and population of the impacted microorganisms all affect how successful they are. The lipophilic nature of the active compounds in EOs, such as thymol and carvacrol, contributes to their antimicrobial activity. This disruption of bacterial cell membranes and mitochondria, inhibition of energy metabolism, and membrane-bound electron flow lead to the breakdown of the proton pump and draining of the ATP pool. These substances enter the phospholipid bilayer of the microorganism and become positioned between the fatty acid chains, making the cell membrane permeable and increasing the fluidity of the membrane due to expansion and destabilisation of the membrane, which decreases passive permeability and reduces the microorganism’s ability to survive. The rate of diffusion through the bacterial cell membrane can also be impacted by the partition coefficient of EOs. Although both gram-positive and gram-negative bacteria are susceptible to the antimicrobial effects of EOs, it has been discovered that gram-positive bacteria are better at causing food spoilage than gram-negative bacteria because gram-negative bacteria have a layer surrounding their cell wall that prevents hydrophobic compounds from penetrating through the lipopolysaccharide layer. Due to their antibacterial properties, EOs from plant compounds including eugenol and coriander, clove, oregano, and thyme are frequently employed as food preservatives. In dairy products, mint oils are utilised as preservatives.
Anti-parasitic activity of essential oils
Essential oils’ anti-parasitic properties have recently been used in the poultry sector as coccidiostats because to the widespread resistance to anticoccidial medications. Alkaloids that fight coccidiosis are abundant in plant species including Dichroa febrifuga and Sophora flavescens. Against Eimeria tenella, Eimeria acervulina, and mixed Eimeria spp., it has been discovered that essential oils from carvacrol, thymol, and oregano are efficient anticoccidials. These substances have a harmful effect on the intestinal mucosa’s upper layer of mature enterocytes because they are hydrophobic in nature. Because they have significant antioxidant properties that stop lipid peroxidation in the gut, EOs from different herbs and spices are beneficial against Eimeria tenella. Garlic (Allium sativum), mint (Mentha spp.), and onion (Allium cepa) are just a few of the plant species whose essential oils have been employed as anti-parasitic medications. Skin scabies are treated with tobacco plant (Nicotiana tabacum) extract. The plant’s EOs can also be utilised as a potential substitute to reduce the animal’s parasite load. Some secondary metabolites from plants are antinutritional. When such metabolites are fed to an animal, it may result in decreased feed intake, toxicity, and even death. Condensed tannin consumption decreases feed intake, decreases digestibility, and impairs rumen metabolism. Therefore, it’s critical to stop EOs’ detrimental impacts on the health and productivity of animals.
Antioxidant activity of Essential oils
Essential oils have inherent antioxidant properties that help protect animals’ bodies from the damaging effects of oxidative stress. They are also applied in the food business to stop the oxidation that results in food waste. It’s possible that EOs’ antioxidant action is connected to their capacity to scavenge reactive oxygen species. Compared to vitamins E, C, and carotenoids, phenolic compounds are proven to be more effective anti-oxidants. Rosemary (Rosmarinus Officinalis), lavender (Lavandula spp.), eucalyptus (Eucalyptus oblique), clove (Syzygium aromaticum), chamomile (Anthemis nobilis), ginger (Zingiber officinale), peppermint (Mentha piperita), and thyme (Thymus vulgaris) are among the essential oils that have been found to be effective against oxidative damage.
Immuno-stimulating activity of essential oils
Essential oils have been shown to have immunostimulatory effects on animals. Examples of these EOs include garlic and oregano. Garlic is added to poultry diets to promote the generation of antibodies against Leptospira Pomona, Pasteurella multocida, and Salmonella enteritidis. Garlic has been found to boost antibody titre against infectious bursal disease virus and new castle disease in broiler chickens. Garlic supplementation in birds enhances lymphocyte proliferation and WBC production, which increases spleen and thymus weight. Garlic’s capacity to promote peritoneal macrophage phagocytosis may be connected to its immune-stimulating properties. They stimulate the synthesis of interleukins, interferon (INF), and tumour necrosis factor (TNF), as well as the macrophages’ secretary metabolism and antigen-presenting cells and antioxidant activity.
Essential Oils with anti-inflammatory properties
Numerous research have clarified how EOs reduce inflammation. The phenolic molecule, which has a potent anti-inflammatory effect, is abundant in essential oils. Curcuma, black pepper, red pepper, cumin, cloves, cinnamon, mint, and ginger extracts all demonstrated potent anti-inflammatory properties. The ability of EOs to scavenge reactive oxygen species, which lessens oxidative damage to tissue and hence reduces inflammation, is thought to be the cause of their anti-inflammatory effects. Most EOs contain terpenoids and flavonoids, which have anti-inflammatory properties. They prevent inflammatory prostaglandins from breaking down. By controlling arachidonic acid metabolism by inhibiting cyclo-oxygenase and lipooxygenase activity, flavonol glycosides and flavonoid aglycons have anti-inflammatory effects on animals.
Effects of essential oils on pigs and poultry
Essential oils from various plant species are utilised to stimulate growth and production in pigs and poultry. They have a favourable impact on the gastrointestinal tract but have varying effects due to variations in the structure and function of the gastrointestinal tract in different species. They make food more palatable, encourage the release of digestive juices, enhance intestinal architecture, and lessen inflammation. A higher sense of flavour stimulates the hunger, which raises feed intake. They consequently enhance an animal’s overall growth. EO effects differ amongst species. Pigs have a strong sense of smell. Due of their powerful odour, they don’t like feed that contains ginger or oregano. Pig and poultry fed on EOs at rates of 24 mg/kg of complete feed and 1–10 g/kg of feed, respectively, have shown improved nutrient absorption. EOs has a good effect on bile production, the secretion of saliva, bile, and mucus, as well as the activity of the enzyme. It also enhances the absorptive surface area and height of villi in the small intestine of pigs and poultry. In pigs and poultry, the antibacterial activity of EOs lessens the negative effects of pathogenic bacteria while fostering the development of probiotic microflora. Additionally, in pigs and poultry, EOs work as an immunomodulating agent and a heat stress reducer. Egg and meat rotting is prevented by the antioxidant capabilities of EOs by lowering lipid oxidation.
Effects of Essential Oils in Ruminants
Due to the emergence of antibiotic resistance and its transmission to humans, concern over the use of antibiotics in ruminants has grown over the past several years. The researcher is looking into antibiotic alternatives to increase ruminant production and feed efficiency. Due to their antibacterial qualities, essential oils can be utilised as an alternative to antibiotics. Ruminant nitrogen and energy utilisation is improved when essential oils are consumed at a rate of 0.2 to 2g/kg of feed. They lessen the formation of ammonia nitrogen and amino acid deamination in the rumen, as well as the inhibition of ruminal fermentation, which reduces the overall creation of volatile fatty acids. The active ingredient in EOs specifically blocks ruminal methanogenesis, which lowers methane generation. High dosages of EOs make these reactions obvious. The active ingredients in EOs boost feed efficiency, favourably affect rumen fermentation, and support wellness. The environment and animal production benefit from the introduction of new EOs in ruminant nutrition.
Conclusions
Essential oils and the molecules they contain work well as antibacterial, anti-inflammatory, immune-stimulating, and antioxidant agents. As feed additives, these substances are regarded as safe. When an animal experiences resistance issues or unfavourable side effects from chemical substances like antioxidants or antimicrobials, essential oils and their components can be employed as natural, non-antibiotic growth boosters.
