The support of immune development in animals is significant for the maintenance of animal health and production, which is of vital importance to the food industry. A balanced diet, a hygienic environment, health management strategies such as biosecurity and vaccination, and natural feed additives such as essential oils (EOs) can all contribute to the development and maintenance of a robust immune system in animals. Some EOs have antimicrobial activity, support respiratory and mucosal health and have an immunomodulatory effect that can help animals resist infection and disease and improve their overall health and well-being.
The long-term health and performance of animals depend heavily on the development of their immune systems. Proper nutrition, appropriate vaccination programmes and natural feed additives such as EOs can help to improve their immune response. For example, some natural feed additives, such as Aromax®, have been shown to boost the immune response, reduce inflammation, have a beneficial effect on the gut and can increase the production of IgA.
1. What are the benefits of supporting immune development in animals?
Animal husbandry and production are critical components of the food industry, providing a reliable supply of meat, milk and eggs for human consumption. In order to maintain animal health and performance, including the farm to fork concept, it is essential to support the development of their immune systems.
Proper nutrition, a hygienic environment and health management strategies such as biosecurity and vaccination are all critical factors that contribute to the development and maintenance of a robust immune system in animals. In addition, natural feed additives such as essential oils (EOs), pro-, pre- and post-biotic products with anti-inflammatory and antioxidant properties have shown promise in improving immunity, gut health and overall well-being
2. Immune system and general nutrition
As mentioned above, a balanced diet rich in essential nutrients such as vitamins, minerals and amino acids is necessary to provide the building blocks for immune cell production and function. With concerns over the use of antibiotics and synthetic additives in animal feed, many farmers and researchers are turning to natural alternatives to improve animal health, welfare and performance. EOs in feed additives are one such alternative that appears to be a promising approach.
3. Effects of essential oils on immunity
EOs are volatile, aromatic compounds extracted from a variety of plant species. They have been used in human medicine and traditional animal husbandry for centuries.
One of the main benefits of EOs is their antimicrobial activity (e.g. Witkowska et al.,2013, Poultry Science), which is beneficial in various species, as well as their ability to modulate the immune system.
According to a review published in Biomolecules by Sandner et al. 2020, the current literature, including in vitro and in vivo studies, indicates the potential of various plant EOs as suitable immunomodulators for the alternative treatment of infectious or immune-related diseases. EOs have also gained attention as non-antibiotic growth promoters for use as dietary supplements for livestock and fish. For example, EO supplementation has been shown to improve the immune status of weaned pigs, e.g. increased lymphocyte proliferation rate, phagocytosis rate and higher serum levels of IgG, IgA, IgM, complement (C)3 and C4.
Various studies have shown that EOs such as eucalyptus, tea tree, clove and lavender contain various chemical compounds that have the potential to regulate cytokine production. These small proteins play a crucial role in the pathways of the immune response. By modulating cytokine production and stimulating the production of immune cells, essential oils have an immunomodulatory effect that can help animals resist infection and disease, thereby improving their overall health and well-being.
Especially eucalyptus, peppermint and thyme EOs have been studied for their effects on animal health and performance. These oils contain active compounds such as terpenoids, phenolic acids and flavonoids that can modulate the immune system, reduce oxidative stress  and improve gut health.
4. Synergy of the combination of essential oils and vaccination – an example in broilers and the respiratory system
An interesting approach has been to observe the effect of EOs on the body’s immune response to vaccines. Vaccines are an important tool, not only for individual health, but also for herd immunity.
The studies conducted at the University of Baghdad by Thajel and Ulaiwi et al. [2,3] showed that a combination of natural EOs containing eucalyptus oil, mint oil and thyme oil plus L-menthol can have beneficial effects in broilers after vaccination against Infectious Bronchitis (IB) and Newcastle Disease (ND). According to the researchers, the administration of Aromax® from XVET Germany led to an improvement in the local and humoral immune response in broilers. A higher concentration of immunoglobulin A (IgA) was shown in a study monitoring the effect after ND vaccination (Graphic 1). IgA is essential for promoting local immunity in the respiratory and gastrointestinal tracts.
In addition, lower levels of the liver enzymes AST and ALT, which can indicate liver stress and liver cell damage, were measured. A reduction in these enzymes suggests that this combination of EOs may help to reduce the stress and damage to the liver caused by these vaccines. They also showed that daily administration of this specific blend of EOs as a spray and in drinking water resulted in a strong immune response.
Similar results were observed and summarised by Peterfalvi et al. (Molecules, 2019). There it is quoted that “in broiler chickens, dietary supplementation with a mixture of thyme (Thymus vulgaris), peppermint (Mentha piperita) and eucalyptus (Eucalyptus globulus) EOs [in a specific ratio] at increasing doses linearly increased serum antibody titres to ND, IB and bursal disease viruses on day four after vaccination. On the eighth day after vaccination, antibody titres were significantly higher at certain EO blend doses compared to the control group.”
In addition, the EO blend containing eucalyptus oil, mint oil and thyme oil plus L-menthol has also been shown to have a positive effect on the respiratory system, reducing respiratory symptoms following vaccination against respiratory diseases .
It should be noted that there is still a lack of research on combinations of vaccines and EOs. Some combinations of EOs and vaccines may even have the opposite effect, causing undesirable cross-interactions. Therefore, an appropriate safety interval is recommended.
5. Essential oils and their effect on the digestive system
In addition to its effects on the respiratory system, the combination of natural EOs mentioned above is said to improve the balance of the microbiome in the digestive system and have a positive effect on the morphological development of the gut. Working positively on the characteristics of the digestive system can lead to increased nutrient absorption, which in turn can positively stimulate a stronger overall immune response.
A study published in 2019 by Nameghi et al. suggested that “supplementation of drinking water with a mixture of essential oils (EOB) derived from thyme, peppermint and eucalyptus […] could improve growth performance, humoral immunity and ileal morphology and microflora in broilers”, thus representing “an alternative to antibiotic growth promoters”.
It is worth recalling the interaction between the gastrointestinal tract (GIT) and the respiratory tract. Although they are separate organ systems, both are part of a common mucosal immune system, known as the research concept of the gut-lung axis (Budden et al, 2016) and therefore it must be considered that these organ systems are connected and influence each other.
Own field trials in pigs and calves have also shown similar beneficial effects of EO blends on both digestive and respiratory organ systems.
The long-term health and performance of animals depend heavily on the development of their immune systems. Proper nutrition, appropriate vaccination programmes and natural feed additives such as EOs can help to improve their immune response.
For example, some natural feed additives, such as Aromax®, have been shown to boost the immune response, reduce inflammation, have a beneficial effect on the gut and can increase the production of IgA.
Therefore, various EOs of natural origin and used in the right combination, could potentially serve as an effective adjunct and alternative to antibiotics and synthetic additives in animal feeding concepts.
 Parham et al., Antioxidant, Antimicrobial and Antiviral Properties f Herbal Materials, Antioxidants 2020, 9, 1309; doi:10.3390/antiox9121309
 Faleh Thajel and H. Amjed Ulaiwi. 2017. Effect of Aromax® on performance, local and humoral immunity against vaccination of Newcastle disease in the low management level in broiler chicken. J. of Ento. and Zoo. Stud. 5 (5): 1986-1990
 Ulaiwi, Amjed. (2019). Role of Some Aromatic Essential Oil on Immune Status Against Infectious Bronichitis Vaccine and Lipid Profile of Broiler Chicken. Iraqi Journal of Agricultural Sciences. 50.10.36103/ijas.v50i6.853
 Nameghi et al., Effects of a blend of thyme, peppermint and eucalyptus essential oils on growth performance, serum lipid and hepatic enzyme indices, immune response and ileal morphology and microflora in broilers. J Anim Physiol Anim Nutr (Berl). 2019 Sep;103(5):1388-1398. doi: 10.1111/jpn.13122. Epub 2019 May 20. PMID: 31106919.)
Aromax® = a combination of eucalyptus oil, peppermint oil, thyme oil and L-menthol