Role of Essential Oils in Poultry Nutrition

Ankit Sharma, Amitav Bhattacharyya, P.K. Shukla and Vaibhav Kr. Singh

Department of Poultry Science, DUVASU, Mathura (U.P.), India

Essential oils (EOs) are obtained as a mixture of aromatic oily liquids from plant materials such as leaves, flowers, buds, seeds, twigs, bark, wood, herbs, fruits and roots. In fact, essential oil is a mixture of fragrant, volatile substances and named according to the aromatic characteristics of plant materials from which they are isolated (Oyen and Dung, 1999). Their concentrations and chemical composition of individual compounds are variable. They are obtained by methods like fermentation, extraction or expression, but the most commonly commercially used method is steam distillation (Krishan, 2014). Various EOs used in poultry include oils from oregano (Origanum vulgare), onion (Allium cepa), turmeric (Curcuma longa), lemon balm (Melissa officinalis), peppermint (Mentha piperita), rosemary (Rosmarinus officinalis), sage (Salvia officinalis), cinnamon (Cinnamomum zeylanicum), thyme (Thymus vulgaris), ginger (Zingiber officinale), eucalyptus (Eucalyptus globulus), garlic (Allium sativum), clove (Syzygium aromaticum), fennel (Foeniculum vulgare), mountain savory (Satureja montana), Australian tea tree (Melaleuca alternifolia) and mugwort (Artemisia vulgaris) (Bolukbai et al., 2008).

EOs can be classified into the four main groups

1. Terpenes, related to isoprene:-

Essential oils constituents can be divided into two major groups: terpene hydrocarbons and oxygenated compounds 2. Straight-chain compounds not containing any side chain 3. Phenylpropanoids(benzenederivatives) 4. Miscellaneous group having varied structures not included in first three groups (sulfur or nitrogen-containing compounds).

Benefits of essential oil in poulty Growth

Sahar Abdulhasan (2018) studied the positive effects of two different commercial products (Digestrom® and Poultry Star®) on body performance and the immune response in broiler. Digestrom® contains a blend of oregano, anise and citrus peel essential oils 150 mg/kg of the diet. Carvacrol is the active and main compound of the essential oil blend. Poultry Star® is an Australian product made from a mixture of beneficial bacterial isolates including lactic acid bacteria as well as a mixture of Enterococcus spp., Bifidobacterium spp., Pediococcus spp., Lactobacillus spp. for 2×1011 CFU per kg of probiotics. Supplementation of Digestrom® @ 150 ppm in the diet resulted in improved body performance and increased serum total protein levels. Moreover, both individual and combined application of Digestrom® and Poultry Star® increased the immune response against New Castle Disease virus, with synergistic effects observed with combined treatment. Supplemented with thyme EO @100mg/kg resulted in significantly improved FCR, higherbodyweightgain,livabilityandprofit in broiler production (Wade et al., 2018). There was improvement in growth performance of live broilers when fed with EOs mixture of 200 ppm of anise oil, oregano, clove, rosmarin and turmeric plant (Al–Sultan Zhang et al., 2003). When essential oil mixture @24 and 48 mg/kg diet were fed to broilers, then there was better feed conversion ratio. EOs increase appetite due to their flavours which is very important for young animal to grow. Essential oils stimulatethesecretionofdigestiveenzymes leadingtoimprovednutrientdigestion,feed intake and rate of gut passage (Jamroz et al., 2005). The beneficial impact of essential oils is interlinked with health and immunity due tochangeofgutmicrobiotaanditwillaffect growth performance and welfare (Bento et al., 2013). There was improved feed efficiencywhenthymeEOswasfedtobroiler quails(Denlietal.,2004).Essentialoilsindiet mayactonintestinalmicrofloraaswellason nutrientutilization(Bentoetal.,2013).

Egg Production

EOs supplemented in the diet of layer increase eggshell thickness and protein digestibility but there was no significant effect on performance and yolk fatty acid composition. Overall EO at the low dose of 50 mg/kg in diet of layer may be beneficial (Ding et al., 2017). When thymol and synbiotic were supplemented separately as well as combined, there was improvement in egg weight, egg production and FCR from 24 to 36 weeks of age (Abdel-Wareth et al., 2016). Supplementation of garlic powder in the diet of the layers leads to increased egg production (Canogullari et al., 2010) and increased egg weight (Yalcin et al., 2006). Supplementation of a diet with a mixture of garlic and thyme leads to improving performance of laying hens and egg quality traits (Ghasemi et al., 2010). Under heat stress, EO mixture and organic acid supplementation in commercial layer diets is beneficial to egg weight and immune function (Ozek, 2011). Supplementation of EO mixture at the level of 24 mg/kg diet significantly improved egg production reduced the percentage of cracked/broken eggs, increased feed effeciency (Cabuk et al., 2006b). Deying et al. (2005) reported supplementation of herbal medicine (Ligustrum lucidum and Schisandra chinensis) in diet significantly improved egg production and feed efficiency of layers.

Antimicrobial activity

Essential oils have known for their antimicrobial activity (Smithpalmer et al., 1998). The antimicrobial properties are due to cumulative effect on many different targets invariouspartsofthecellandnotbecauseof one specific mode of action of the chemical compounds present in EOs (Burt, 2004). The exact anti-microbial mechanism of EOs is their chemical structure and lipophilic quality. Terpenoids and phenyl propanoids

reach the inner part of the cell by penetrating inner part of membrane becauseoftheirlipophilicity(Helanderetal., 1998), but it has also been suggested that aromaticity (Bowles and Miller, 1993) and structural properties like presence of the functional groups are responsible for the antibacterial effect. EOs are slightly more effective against Gram +ve as compared to Gram -ve food pathogens (Burt, 2004) because Grame –ve have the outer membrane outside the cell wall which restricts the entry of hydrophobic compounds through its lipopolysaccharide (Vaara, 1992). Many EOs limit many pathogenicbacteriainpoultryandstimulate growth of beneficial microbes (Wenk, 2000). It was also noticed that cinnamaldehyde inhibits enzymes that synthesise fungal cell wall(Bangetal.,2000).

Antioxidant activity

EOs donate hydrogen or an electron to free radicals and delocalize the unpaired electron within the aromatic structure, thus prevent other biological molecules from oxidation (Fernandez-Panchon et al., 2008). Thymol has high antioxidant activity because of the presence of phenolic -OH groups which act as hydrogen donors to the peroxy radicals produced during the first step in lipid oxidation, thus decreasing the hydroxy peroxide formation. Thymol and carvacrol when given in diet can act as antioxidant in egg and meat of chickens (Lee et al., 2004). It is found that phenolics are more potent antioxidants as compare to vitamins E and C and carotenoids (RiceEvans et al., 1997). Diet of EOs containing carvacrol, capsicum oleoresin and cinnamaldehyde show antioxidant property by improving the concentration of carotenoids and coenzyme Q10 in liver when fed to broilers (Karadas et al. 2014). EOs increases oxidative stability of meat and eggs that contain high fat content by reducing the degree of un-saturation (Botsoglou et al., 2002).

Antiparasitic activity

Many plants and their EOs have antiparasitic activity e.g., EOs and seeds of garlic (Allium sativum), mint (Mentha spp.) and onion (Allium cepa ) are effective against GIT parasites. It was reported that the phenols can be used as ocysticides against E. tenella (Williams, 1997). EOs can exert insecticidal and repellent effect against flour beetles when added to the mixture of grains. Origanum acutidens oils have thymol, carvacrol and P-cymene when added to grain mixtures shown insecticidal activity against Tribolium confusum (Confused flour beetle) and Sitophilus granaries (grain weevil) causing 37% and 68% mortality respectively (Kordali et al., 2008) in adult insects. The chief ingredients of oregano oil are Carvacrol and thymol, they have anticoccidial action against mixed Eimeria spp. infection (Oviedo-Rondon, 2006) and E. tenella (Giannenas et al., 2003).

Anti-inflammatory activity and immunomodulatory effect

The major EOs substances having antiinflammatory abilities are the terpenoids and flavonoids. These substances reduce the metabolism of inflammatory prostaglandins. The phenolic compounds present in essential oils have strong antiinflammatory qualities (Craig, 2001). Some essential oils enhance lymphocytic activity, promote production of immunoglobulins and boost interferon-γ release (Awaad et al., 2010; Gopi et al., 2014). Hanieh et al. (2010) suggested that this could be due to ability of garlic to enhance the production of interleukins, interferon (INF-γ) and tumor necrosis factor (TNF-α). Saleh et al. (2014) observed that there was an increased antibody production, when thyme and ginger oils @100 and 200 mg per Kg feed respectively given. Diets supple-mented with essential oils containing herbal mixtures increase the activity of the intestinal lymphatic system. Placha et al. (2014) observed that thyme oil @0.5g per kg of feed significantly increased level of IgA. Awaad et al. (2010) in their experiment revealed that when eucalyptus and peppermint essential oils added to water at the rate of 0.25 ml/L results in an increased both humoral and cell mediated immune response.

Flavouring agent

When compared to pigs, poultry may not immediately respond to flavour (Moran, 1982). There is evidence that flavours could affect feed intake. But the effect of flavours on poultry performance is considered as negligible (Moran, 1982). Therefore, effect of EOs as flavouring agent in poultry nutrition needs to be observed.

Digestion and respiration

Essentialoilshelptoimproveproteindigestion byincreasingthesecretionofhydrochloricacid and pepsin (Gopi et al., 2014). Essential oils stimulate digestive secretions such as bile and mucus and enhanced enzyme activity (Platel, 2001). In broilers, EOs increase the secretion of trypsin,amylaseandjejunalchymeandreduce theadherenceofpathogens(e.g.,E.coliandCl. perfringens) with intestinal wall (Jamroz et al., 2006). Hypocholesterolemic effect in lemongrass oil is due to the inhibition of hepatic 3–hydroxy–3–methylglutaryl coenzyme A (HMG–CoA) reductase activity; a key regulatory enzyme in cholesterol synthesis (Crowell, 1999). Essential oils that affect the respiratory system are oils of peppermint and eucalyptus, which thin the mucus and get rid of it from airways. Eucalyptol and menthol in these oils have antispasmodic and expectorant effects. So airways are cleared and breathing during inflammation becomes easier (Durmic and Blache, 2012).

Conclusion

The EOs and their compounds have antiparasitic, anti-inflammatory, immunomodulating, hypolipidemic and antimicrobial activity. These oils reduce the loss during the meat processing due to their antioxidant property because antioxidant property provides an effective protection against the drip loss during the prolonged low temperature storage which increases the acceptance among the consumers and reduce losses in meat processing plant. So it plays a role in improving the keeping quality and durability of raw as well as processed meat. There are variations among results done by many researchers who have conducted work on the nature and use of EOs in the poultry nutrition. Toxicity of essential oils has been reported only at higher inclusion levels. EOs have certainly positive effects. However, comprehensive studies on their use in poultry nutrition is still not enough and studies are needed to assess the mode of action, exact supplementation level and their interaction with feed ingredients. Further studies are also needed on synergestic as well as antagonistic action of different essential oils when used in combination in different species ofpoultry, r