Poultry and Herbs

BENEFICIAL APPLICATIONS OF HERBS IN POULTRY

Among all other classes of livestock, poultry industry has been growing persistently over years around the globe with more developments in the last fifty years by providing globally important sources of animal proteins (Byarugaba, 2007). Globally, production of the primary poultry products (meat and eggs( has been rising rapidly. Over a 10 year period between 1995 and 2005, consumption and hence production, has increased globally with the following percentage increases for chicken meat (53%), turkey meat (13%), duck meat (67%), goose meat (53%), chicken eggs (39%) and other eggs (27%) (Scanes, 2007). They are amongst the most intensively reared of all livestock species with the developments especially in the areas of nutrition, disease control, genetic improvement, management and organization of dietary requirements (in precise terms of energy, amino acids, minerals and vitamins), selection and cross-breeding techniques, along with large scale poultry production and vertical integration (Smith, 1990; Adu, 1997; Mirzaei-Aghsaghali, 2012). But, the intensity of husbandry can only be done by controlling many infectious diseases and growth and production disturbances that would otherwise inflict severe losses or even thwart intensive poultry sector. The emergence of new pathogens or one variant of an old pathogen has the potential to spread rapidly and devastate the entire flocks (Byarugaba, 2007; Scanes, 2007).

Since time immemorial, plants and plant parts have been serving as an indispensable source of medicine for indigenous poultry production systems. Conventional disease prevention methods are geared towards birds in confinement and not free range in an indigenous poultry production system. However, the existing indigenous technical knowledge inherited from past generations has sustained the local poultry production system (Hashemi and Davoodi, 2012; Mirzaei-Aghsaghali, 2012). This knowledge is passed on verbally and is hardly documented. Due to high cost of conventional medicines and vaccines coupled with the lack of knowledge on their use, these drugs are usually out of reach of the small-scale farmers. There is, therefore, need for cheap, easy to use and sustainable local poultry disease control programs (Okitoi et al., 2007; Adu et al., 2009; Mahima et al., 2012). The inherent utility and practical applications of indigenous medicinal herbs/plant extracts (garlic, cinnamon, tulsi, ginger, turmeric, lemon, neem, yucca, thyme, rosemary, etc.) are being explored for improving poultry health as well as production with fruitful results (Sudarshan et al., 2010; Umashanker and Shruti, 2011; Mahima et al., 2012; Khan et al., 2012a-c; Sridhar et al., 2014).

Herbal medicines as antimicrobials for poultry: The practice of pharmacological treatment of disease conditions began with the use of herbs (Tyler, 2000) and most of the drugs in vogue to treat bacterial and other infections were first isolated from ethno-medicinal plants and other natural sources (Coe and Anderson, 1996). Antimicrobials based on herbal origin represent a vast untapped source of medicines with tremendous therapeutic potential (Cowan, 1999). The indiscriminate use of conventional antimicrobials has led to a steady increase in the drug resistance and the low-income countries, home to the majority of the world’s population are particularly affected by this phenomenon (Radyowijati and Haak, 2003). Antibiotic resistant strains of bacteria are an increasing threat to animal and human health with resistance mechanisms having been identified and described for all known antimicrobials in vogue (McDermott et al., 2002). This, therefore, necessitates a newer alternative for antimicrobial substances and many plants have been shown to possess antimicrobial traits which are chiefly synthesized during secondary metabolism of the plant (Kokoska et al., 2002; Radyowijati and Haak, 2003; Rusenova and Parvanov, 2009).

Neem (Azadirachta indica) is one of the most prominent herbal medicines with different biologically active principles like azadirachtin, nimbin, salanin, meliacin etc. and many other derivatives of these principles which belong to natural products called triterpenoids (NRC., 1992; Ansari et al., 2012b). The A. indica leaf exhibits potent antimicrobial action as it has proven its, anti-bacterial, anti-viral, anti-malarial, anti-fungal and anti-oxidant properties in various experimental studies in poultry (Chakraborty et al., 1989; Subapriya and Nagini, 2005; Ansariet al., 2012a). Neem oil selectively activates the cell mediated immune response by activating macrophages and lymphocytes have been reported effective as a potent bio-insecticide. Apart from this, it exhibits a wide range of other pharmacological activities viz., anti-inflammatory, anti-hyperglycaemic, anti-ulcer, anti-mutagenic, anti-carcinogenic, immunomodulatory and various other properties without showing any adverse effects (Ganju et al., 2003; Chauhan, 2010; Chakraborty and Pal, 2012).

Essential oils derived from plants have provided enough evidences to suggest as a tool in defending bacterial diseases in poultry (Dorman and Deans, 2000; Rota et al., 2004; Gopi et al., 2014). They consist of complex mixtures of secondary plant metabolites like phenylpropenes and terpenes, they are particularly associated with characteristic plant fragrances and essences. Essential oils can be applied as potential feed additives for the prophylactic action against microbial infections (Mourey and Canillac, 2002; Cabuk et al., 2006; Brenes and Roura, 2010). Among the various essential oils, thyme, oregano and garlic have shown to be the most pronounced antimicrobial activity (Williams and Losa, 2001; Iten et al., 2009; Khan et al., 2012b). Thyme oil and its components (thymol and carvacrol) demonstrated high antimicrobial activity against most of the poultry pathogens that include Staphylococcus aureus, S. epidermidis, Pseudomonas aeruginosa, Bacillus cereus, Escherichia coli, Salmonella enteritidis, S. typhimurium etc. (Smith-Palmer et al., 1998; Al-Bayati, 2008; Bolukbasi et al., 2008; Sokovicet al., 2010; Levic et al., 2011). The essential oil from Origanum vulgare which is obtained by steam-distillation of its leaves and flowers is well known for its antimicrobial activity along with potent antifungal, antioxidant and insecticidal activities (Florou-Paneri et al., 2005; Marcincak et al., 2008; Bozkurt et al., 2012a). Oregano has shown to be an excellent alternative for ionophore antibiotics thereby providing protection against E. tenella infection in birds (Giannenas et al., 2004). A study conducted in live birds showed that certain primary components namely curcumin, piperin, thymol and eugenol of the Curcuma longa (turmeric), Piper nigrum (black pepper), Thymus vulgaris (thyme) andSyzygium aromaticum (clove), respectively are effective in the control of Clostridium perfringens, an important enteropathogenic bacteria(Mitsch et al., 2004). Garlic (Allium sativum) possesses excellent antimicrobial properties which have been proven by various researchers (Rajendhran et al., 1998; Kim et al., 2009; Jacob and Pescatore, 2011; Rehman et al., 2011). The aqueous extract of garlic has been shown to inhibit E. coli and Salmonella Typhimurium in vitro (Singh and Shukla, 1984; Kumar and Berwal, 1998). In vitro antimicrobial activity againstE. coli has been shown by cinnamon oil that necessitates further in vivo studies for possible benefits in poultry production (Friedman et al., 2004; Griggs and Jacob, 2005). A variety of other plant based remedies have been proven to possess antimicrobial effect and an important one among them is the aqueous extract of the seeds of Carica papaya which lyse bacteria using the enzyme papain (Fajimi and Taiwo, 2005; Pushpangadan, 2006; Adu et al., 2009).

Herbs as antiviral agents for poultry: Herbal preparations are gaining more importance in the search for anti-viral agents because of their wide spread availability and easy incorporation in the diet (Kitazato et al., 2007). Deva-5 is a herb formulation composed of five herbs namely Momordica cochinchinensis L., Gentiana decumbens L., Polygonum bistorta L., Hypecoum erectum L. and Terminalia chebula Retz showed in vitro antiviral activity against avian influenza A virus subtype H3N8 (Rajasekaran et al., 2013; Oyuntsetseg et al., 2014). Makau et al. (2013) reported that Alchemilla mollis extract showed potent anti-influenza activity against influenza A virus subtypes namely H1N1 and H5N1 by inhibiting influenza virus replication. A. mollis extract synergistically potentiates the anti influenza effect of zanamivir. Many phyto-chemicals such as pentagalloyl glucose (PGG( and oligonol a low molecular weight polyphenol derived from lychee fruit extract showed strong anti-influenza activity by inhibiting virus entry into host cells, inhibits reactive oxygen species-dependent ERK phosphorylation, blocking the extracellular signal-regulated kinase phosphorylation results in inactivation of the virus (Gangehei et al., 2010; Liu et al., 2011). Watanabe et al. (2011) demonstrated that valtrate from Valerianae radix and 1'-acetoxychavicol acetate from Alpina galangal showed anti-influenza activity by preventing the nuclear export of viral ribonucleoprotein results in inhibition of virus replication.

Ou et al. (2013) investigated the therapeutic effects of the combined extracts of Rhizoma Dryopteridis Crassirhizomatis and Fructus Mume(RDCFM) against Infectious Bursal Disease Virus (IBDV) infection. They reported that the herbal extracts increased the survival rate, antibody levels and relative body gain and significantly decreased the virus loads in bursa of Fabricius. The active substances namely proto catechuic acid and 4-hydroxycinnamic acid isolated from Fructus Mume (FM) were established as effective against infectious bursal disease virus by enhancing the protection and increasing the immune response for chickens (Ou et al., 2011, 2012; Okwor et al., 2012). Liu et al. (2009) reported that sweet wormwood (Artemisia annual L.) extracts inhibited the Newcastle Disease Virus (NDV) proliferation in chicken embryos without causing side effects. Most of the herbal preparations contain various bioactive molecules namely flavonoids, polyphenols, lignans and alkaloids which shows many pharmacological activities such as anti-bacterial, anti-inflammatory, anti-fungal, anti-oxidant and analgesic properties. Sood et al. (2012) reported that Eugenia jambolana extracts showed 100% virucidal activity against highly pathogenic avian influenza (H5N1) virus in chicken embryonated eggs (ECE) inoculated in-ovo and in tissue culture. Eucalyptol, menthol and ormosinine showed anti-influenza activity due to its potent interactions with the viral HA protein (Gangopadhyay et al., 2011). Essential oils derived from peppermint and eucalyptus showed protective action in broilers against multiple respiratory pathogens mainly Mycoplasma gallisepticum and H9N2 influenza virus infections (Barbour et al., 2006, 2011). Lee et al. (2012a) reported that supplementation of lyophilized green tea by-product extract namely, catechins in feed or drinking water decreases replication and excretion of H9N2 virus from chickens in a dose-dependent manner. The anti-influenza activity of catechins is mainly due to direct interaction with viral HA and inhibition of viral RNA synthesis (Song et al., 2005). Zhai et al. (2011) and Jiang et al. (2012) reported that oral administration of ginseng stem and leaf saponins andHypericum perforatum L. in feed or drinking water significantly increased the serum antibody response to Newcastle disease, inactivated H5N1 and H9N2 vaccines in chickens.

Major disadvantages of herbal therapy are some herbal derivatives namely ginseng saponins need 4-6 years to purify and is very costly in the market (Zhai et al., 2011). Methods of the extraction and preparation of the crude extracts and its purity greatly influence the inhibition activity of some herbs against infectious organisms. Extensive works are needed to explore the herb-drug interactions, potential toxicity and methods for identifying the active components.

Herbal medicines as anti-coccidiosis in poultry: Due to vast usage of sulphanilamide, ionophorous antibiotics, amprolium or synthetic chemical compounds for the treatment of coccidiosis in poultry results in emergence of drug-resistant strains and antibiotic residues in poultry meat posing serious problems to the meat consumers. To overcome this major threat, safe alternative anti-coccidial herbs preparations are required for the treatment and control of avian coccidiosis. Several herbs possess anti-coccidial effects namely Sophora flavescens Aiton, Ulmus macrocarpa, Bupleurum chinese DC, Sinomenium acutum, Artemisia asiatica, Pulsatilla koreana, Artemisia annua Linne, Quisqualis indica, Foeniculum vulgare, Torilis japonica and Galla Rhois powder increases survival rates and body weight gains of birds, reduces bloody diarrhea symptoms and oocyst excretions from birds infected by Eimeria tenella (Youn and Noh, 2001; Lee et al., 2012b; Zhanget al., 2012; Dragan et al., 2014). Chandrakesan et al. (2009) and Arczewska-Wlosek and Swiatkiewicz (2012) evaluated the anti-coccidial activity of some herbal extracts blend containing Salvia officinalis (sage), Solanum nigram, Allium sativum (garlic), Moringa indica, Thymus vulgaris(thyme), Echinacea purpurea (echinacea), Aloe vera, Mentha arvensis and Origanum vulgare (oregano) against E. tenella, Eimeria acervulina, E. necatrix and E. maxima. The extract known as febrifugine contains a quinazolinone alkaloid, halofuginone derived fromDichroa febrifuga has been reported to possess anti-coccidial and anti-malarial activity (Youn and Noh, 2001). Three plant extracts namelyTulbaghia violacea (35 mg kg-1), ch Artemisia afra (150 mg kg-1) and Vitis vinifera (75 mg kg-1) showed anti-coccidial action due to its antioxidant activity. T. violacea significantly reduced the oocysts production in birds; it can be used as prophylactic or therapeutic anticoccidial agent (Naidoo et al., 2008). Therefore, the search of herbal drugs for anti-coccidial treatment gains promise as an alternate in the control of coccidiosis.

The ethnoveterinary usage of herbs in managerial practices for countering common disease conditions of chickens is presented in Table 1.

Herbal medicines against Ecto-and Endo-parasites in poultry: Throughout the world arthropods have been found to inflict immense loss to the poultry industry. Birds are often affected by ecto-parasites which may be continuous or temporary. Continuous external parasites are those that spend all of their adult life on the host and that commonly include sticktight fleas, chicken body lice, scaly leg mites and northern fowl mites. Temporary external parasites are those which feed on the hosts but do not live on them. Common temporary external parasites of poultry include fowl ticks (also known as blue bugs), bed bugs and chicken mites (also known as red mites or roost mites). The use of chemicals viz., hydrocarbons, organophosphorus, carbamates and pyrethroids are found not to be free from adverse effects of toxicity to human, added up drug resistance by target parasites and high cost of drugs, paving the way for herbal alternatives. Commercial phytomedicinal preparation like Pestoban is found to be effective against wide variety of poultry lice viz. Cuclotogaster heterographa;Lipeurus caponis; Menopon gallinae and Menocanthus apamineus; Goniocotes gallinae (Das et al., 1993; ICAR., 2002; Fajimi and Taiwo, 2005; Adu et al., 2009). For controlling lice infestation in poultry, the stem and leaf extract of tobacco (Nicotiana tabacum) also showed a 100% efficacy by the 2nd day of application on skin (Fajimi et al., 2001). Pawpaw leaves when burnt into ashes can be used as a topical agent to control lice in poultry (Nwude and Ibrahim, 1980). Lice can also be controlled by powdered seeds of Annona squamosa and Tephrosia vogelli. Topical application of 10% aqueous extract of garlic is shown to be an effective way to decrease mite infestation in birds (Jacob and Pescatore, 2011). Cinnamon oil has shown anti-parasitic activity against Trichomonas, Histomonas meleagridis and head lice in chicken (Zenner et al., 2003). Allium cepa (onion) has proven pronounced anti-parasitic activity against many helminthes and protozoa such as,Trichinella spiralis and Leishmania sp. For preventing lice in ducks, drop the bulb in the bird’s drinking water and for chickens green leaves (spring onions) can be used to be picked by the birds (Gefu et al., 2000).

Among the internal parasitic diseases in poultry, avian coccidiosis is the most wide-spread disease which is mainly controlled by the use of chemotherapeutic agents. Now the emergence of drug-resistant strains demands the need for an alternative and potential control strategy mainly based on herbal remedies. Most widely used and proven herbal anticoccidials include Aloe vera, Aloe spicata, Allium sativum,Azadirachta indica, Ficus burkei, Lannea stullmanni, Myrothamnus flabellifoilius, Capsicum annum etc. (Elbanna et al., 2012; Kanakaraju et al., 2013). Neem extract contains the chemical Azadirachtin which has a significant efficiency on pests, deformental effect on viruses, mites, fungal pathogens, plant parasitic nematodes, intestinal worms, bacteria, mollusks and protozoan parasites such as coccidian species (NRC., 1992; Biu et al., 2006). Dietary incorporation of Azadirachta indica (neem) and Artemisia annua at levels of 10 and 5%, respectively was shown to affect the broiler performances and possess anticoccidial potency against Eimeria tenella (Hady and Zaki, 2012). It has been proven that the latex of Carica papaya has reasonable pharmaco therapeutic properties against intestinal nematodes of poultry especially, Ascaridia galli, Heterakis gallinanum, Capillaria spp., etc. and a dose rate of 1200 mg papaya latex per bird is formulated as an effective anthelminthic preparation (Fajimi et al., 2001). Also the aqueous extract of the seeds of Carica papaya has shown 90% efficacy towards other helminthes like Oesophagostomum, Trichuris and Trichostrongylus, because of the action of papain on them (Fajimi and Taiwo, 2005; Adu et al., 2009).Citrus aurantifolia (lime) can prevent worm infestation when its juice is mixed with drinking water (Fajimi et al., 2001). Amaranthus spinosusis a vermifuge through its ethanolic extract against Strongylus sp. and Trichuris sp. s0 (Assiak et al., 2001). Regular addition of garlic into the drinking water is an effective control measure for intestinal worms and coccidiosisin poultry (Jacob and Pescatore, 2011). Chopped seeds of pumpkin (Cucurbita moschata) are shown to be good for the control of tapeworms in laying hens (Jacob and Pescatore, 2011). Herbal immunomodulators that contain holy basil (Ocimum sanctum); mango (Mangifera indica); Indian gooseberry (Phyllanthus emblica); ginseng (Withania somnifera) and Shilajit (Asphaltum puniabiunum) when used experimentally, have shown to fight caecal coccidiosis in poultry (Pangasa, 2005).

Regano, a natural extract of a specially selected cultivar of Oreganum vulgare gave effective protection against the coccidiosis challenge. The level of protection achieved by the Regano was similar to the protection provided by Salinomycin at 55 g/MT (Saini et al., 2003).

Pasture management is considered as one of the best practices to prevent parasitic infestation and pasture rotation will break the life cycle of worms. Some of the pasture plants that can be planted are: Wormwood, Peppermint, lemon grass (Citronella) etc. By planting these plants around the coop area, birds will eat and walk on the leaves assisting with internal and external parasite eradication. Also they form large clumps of aromatic long leaves keeping flies, fleas and mites away from the coop area. Birds eat the tips and brush against the bushes when planted close by around the poultry shed to control parasites.

Immunomodulatory herbs for poultry: Over the past few decades, vigorous emphasis has been made for enhancing the growth and production performances in the poultry industry which badly resulted in an adverse effect on the immunological parameters of poultry, thereby damaging the natural defensive mechanism against various microorganisms including viruses, bacteria, pathogenic fungi, ecto and endo-parasites and various toxins etc. Due to development of antibiotic resistance by the bacteria and pathogenic microbes researchers are now thinking towards immunomodulation. Nowadays, immune-based therapies are gaining more importance than monovalent approaches which are having limited benefits (Hashemi and Davoodi, 2012). Apart from the actions like treating diseases, control of ecto- and endo-parasites, fertility enhancement, bone setting and poor mothering management, an array of herbal medicines have been reported with immunomodulatory effects like histamine release, modulation of cytokine and immunoglobulin secretion, class switching, cellular co-receptor expression, lymphocyte expression, phagocytosis etc. (Spelman et al., 2006; Mahima et al., 2012).

Modulation of immune response to alleviate diseases has since long been of great interest to researchers (Sharma, 1983; Spelman et al., 2006; Ozek et al., 2011; Mahima et al., 2012). Indian medicinal plants are a rich source of substances which are claimed to induce immunity, thereby stimulating the non-specific immunomodulation, essentially granulocytes, macrophages, natural killer cells and complement functions (Hashemi and Davoodi, 2012; Mirzaei-Aghsaghali, 2012). Immunomodulation using medicinal plants provides an alternative to conventional chemotherapy for several diseases, especially when suppression of inflammation is desired (Mahima et al., 2012). Herbal medicine relies on active plant chemicals with biological properties. Many conventional medicines are synthetic compounds designed to mimic the action of plant chemicals. Recently, there has been progress on the ethno-medicinal plants as immunomodulatory agents because of the fact that plant extracts have been widely investigated during last few decades in different parts of the world for their possible immunomodulatory properties. In due course, several studies have demonstrated the isolation of potential bioactive molecules having influence on immune system and few have been tested as herbal formulations (Ahmed and Bassuony, 2009; Akerreta et al., 2010).

There are various natural adjuvants and synthetic agents which have been used as immune stimulants (Levamisole, Thalidomide etc.) but they are proven to possess various side effects. On the other hand, the conventional plant immunomodulators are safer, cheaper and much more effective. So herbal medicines are being used as immunomodulators and have alternative potential for the conventional chemotherapy against a variety of diseases especially in relation to host defense mechanisms. Several plant extracts, compounds and formulations have also been patented and this include various polysaccharides, lectins, peptides, flavonoids and tannins which are used in various in vitromodels to assess their immune responses (Cherng et al., 2008). In literature, many plants have been listed; having immunomodulatory effects and some of them have been proven using modern scientific methodologies (Barnes et al., 2007).

Ashwagandha ( Withania somnifera) is one of the well-known medicinal plants which has been used amply for centuries in Ayurvedic medicine to increase longevity and vitality (Choudhari et al., 2006; Winters, 2006). Several bioactive compounds have been isolated from this plant, among which the important one is the steroidal lactone called Withanolides, having antibacterial, antiviral, antitumor and immunomodulatory activities (Elsakka et al., 1990; Jayaprakasam et al., 2003; Shisodiya et al., 2008; Shirin et al., 2009). From the study conducted by Bani et al. (2006), it has shown that the oral administration of W. somnifera extract selectively skewed the immune responsetowards Th1 response cells rather than Th2 cells by increased IFN gamma and IL-2 versus IL-4 cytokines levels. Besides increasing the expression of T-helper1 (Th1) cytokines, it modulates the immune response by augmenting the CD4 and CD8 counts and Natural killer (NK) cell activity (Davis and Kuttan, 2002; Khan et al., 2006). This indicates its unique immunomodulatory profile which suggests that it is having stimulatory effect on T lymphocytes, its subsets and B-lymphocytes involved in antibody synthesis (Benacerraf, 1978; Dean et al., 1979; Lusteret al., 1982; Bani et al., 2006). Bhardwaj et al. (2012) showed that the supplementation of Ashwagandha root powder at the inclusion rate of 1 percent in poultry diets is found optimum for significant effect on body weight, Feed Conversion Efficiency (FCE), haematological parameters and improving the general health status of birds. Its hydro-alcoholic root extract has shown antiviral activity against IBD Virus replication (Pant et al., 2012). Administration of W. somnifera extract to broiler chick diets resulted in an increase in Hb, PCV, TLC and antibody titre against viral diseases like IB and IBD, suggesting the improvement in hematological profile and immunological status of the birds (Mushtaq et al., 2012; Pant et al., 2012). Mice treated with W. somnifera and radiation showed a 143.6% increase in bone marrow cellularity and maintained the levels of normochromic and polychromic erythrocytes compared to mice being treated with radiation therapy alone (Devi et al., 1996; Kuttan, 1996; Ganasoundari et al., 1997; Winters, 2006).

The herb Tinospora cordifolia (Family, Menispermaceae) belongs to a group of medicinal plants that grows in the tropical and subtropical regions of India (Sengupta et al., 2011). It is a large glabrous climber with succulent corky stem, sub deltoid cordate leaves, branches sending down and pendulous fleshy roots. Guduchi is also well known for its immunomodulatory, antioxidant, antibacterial and antiviral properties, activates macrophages and cytokine production and its extract has been found to have wide use in the Indian System of Medicine for a variety of diseases (Kapil and Sharma, 1997; Prince and Menon, 2003; Srinivasan et al., 2008). It can act as an immune prophylactic agent and induces disease resistance properties by boosting general immunity to fight against diseases, prevents oxidative damage, help recruitment of macrophages in response to tumor growth, increases leukocyte counts and reduces cyclophosphamide induced neutropenia (Bishayi et al., 2002; Chakraborty et al., 2010). Activation of the immune system by the novel (1,4)-alpha-D-glucan from Tinospora cordifolia occurs via the activation of macrophages that occurs through TLR6 signaling and NF kappa B translocation along with cytokine responses (Rege et al., 1999; Nair et al., 2006). The water soluble fraction of T. cordifolia leaf fraction is found as an immunoprophylactic agent due to its immunostimulatory and disease resistance properties (Alexander et al., 2010). Guduchi can be used as a good alternative to costly allopathic medicine in boosting the immune functions in intoxicated conditions and can effectively complement allopathic medicines in diseased state (Sengupta et al., 2011; Bhalerao et al., 2012). Crude extract of Tinospora cordifolia contains a polyclonal B cell mitogen which enhanced immune response in mice (Alamgir and Uddin, 2010). It also prevents oxidative damage, induced by peroxy nitrite, wherein the action was similar to selective inhibitors of Reactive Oxygen Species (ROS) like mannitol, superoxide dismutase, sodium azide and antioxidants, GSH and vitamin C (Desai et al., 2002; Prince et al., 2004; Mirzaei-Aghsaghali, 2012). Moreover, T. cordifolia increases the leukocyte counts and reduces the neutropenia induced by single and multiple doses of cyclophosphamide (Thatte et al., 1987; Singh et al., 2006). It was reported that T. cordifolia can stimulate production of cytokines like IL-1 and TNF (Dahanukar et al., 2000) which are having important role in hematopoiesis (Mochizuki et al., 1987; Guilbert et al., 1993; Singh et al., 2006; Upadhyaya et al., 2011; Kumar et al., 2013a).

Neem (Azadirachta indica) is another immunomodulatory herb, that has shown marked influence on the haematological parameters in birds like haemoglobin, PCV and RBC indices (Khan and Zafar, 2005; Ansari et al., 2012b). It may be due to hepato-stimulatory and hepato-protective effects of neem leaves resulting in the synthesis of more haemoglobin (Hb) in the bone marrow (by erythropoietic factors released by hepatic cells), there is much more increase in the Hb concentration (Talebi et al., 2005). It has been proven to be beneficial in immunosuppressed conditions like Infectious Bursal Disease (IBD), in poultry. Feeding of powdered dry leaves of A. indica was found to be effective on humoral and cell mediated immune responses, in a flock of broilers which had survived an outbreak of IBD. Renu et al. (2003)has shown that the administration of Neem leaf extract enhanced cell mediated immune response (as observed by DTH in term of increased skin thickness to 2,4-dinitro-chlorobenzene in skin contact sensitivity test) and improved humoral immune response against NDV antigen (as detected by indirect ELISA), indicating its immune potentiating effect (Haq et al., 1999; Ansari et al., 2012a). Studies conducted on the immunomodulatory potential of the above three herbs (ain W. somnifera, T. cordifolia and A. indica) against chicken infectious anaemia, an immunosuppressive viral disease of young chicks, revealed that these herbs have excellent capacity in stimulating both the cellular and humoral immune responses in chicks against the causative virus and also ameliorating effects on viral pathogenesis were observed (Latheefet al., 2013; Latheef et al., 2013). On assessing the viral load in target organs, using the real time PCR technique, it was found that the viral load in herbal treated birds reduced almost up to 50% compared to the control group, thereby resisting viral multiplication in those organs (Latheef, 2013).

Wild mint (Mentha longifolia) has been found to enhance immunity especially in broiler chicks in addition to the improvement in growth performance, feed conversion ratio and gross return. The active virtues of this particular herb depend on the abundance of volatile oil containing thymol (hydrocarbon) in addition to higher oxygenated compounds. The polysaccharides obtained from four Chinese plants (Astragalus root, Isatis root, Achyranthes root and Chinese Yam( significantly improved antibody titres in vaccinated chicken. Due to the presence of low molecular weight polysaccharides like acyranthan (ACH) and astragalan (APS), they can be used as feed additives to improve immunity of broiler birds (Alzorekya and Nakahara, 2003; Chen et al., 2003; Durrani et al., 2008; Khaligh et al., 2011; Okokon et al., 2012). In another study, herbal formulation containing extracts of Asparagus racemosus was proven effective to be recommended for use as a positive immunomodulator in normal and immuno-compromised broiler chicks (Kumari et al., 2012).

Herbs and spices rich in flavonoids, vitamin C and carotenoids generally have more beneficial effects on immune system. Those plants containing these molecules of immunostimulatory properties are Echinacea sp., Glycyrrhiza glabra (Liquorice), Allium sativum (garlic) andUncaria tomentosa (Cat’s claw) and they can improve the functions of lymphocytes, macrophages and NK cells a s well as increase phagocytosis and stimulate the interferon synthesis (Frankic et al., 2009). Echinacea stimulates macrophages, cytokine production, Natural Killer (NK) cells, neutrophil and B-lymphocyte activity. Liquid preparations have been shown to have immune-stimulating property and enhance several white blood cells and phagocytosis (Burton Goldberg Group, 1999) and production of specific IgG in birds. Liquorice is also a potent immunomodulatory with anti complimentary and antioxidant activity (Ablise et al., 2004). Glabridin, one of its active principles, prevents LDL oxidation (Belinky et al., 1998). The components of its root can modulate Bcl-2/Bax (the family of apoptotic regulatory factors) which attributes for their cytoprotective activity (Jo et al., 2004). Cat’s claw (Uncaria tomentosaain) induces p ositive influence on IL-1, IL-6 and IFN-γ production and found to exhibit immune adjuvant activity with pneumococcal vaccine (Winkler et al., 2004). Its anti-inflammatory effects are due to negation of NF-KB activation and suppression of TNF-α synthesis (Sandoval-Chacon et al., 1998; Sandoval et al., 2000). Other actions like modulation of apoptosis, tumor cell proliferation and DNA repair, lead to cyto-protective effect (Sheng et al., 1998) and selectively induce apoptosis, leading to antitumor activity (Sheng et al., 2000). Researchers reported that broilers fed with oxidized fat showed a significantly increased concentration of tocopherols, beta-carotene, lutein and retinol in plasma and tissue. Also, essential oils extracted from medicinal plants improve the immune response and also are able to cause changes of the duodenal mucosa with beneficial effects for the animal (Stef et al., 2009).

Conflicting reports are available regarding the efficacy of herbs producing immunomodulating effects on poultry. The reason may be attributed to the mechanism of action of plant extracts, the desirable effects of these extracts mainly depend upon the structure and level used in addition to the metabolism (Barreto et al., 2008). Second, it is difficult to precisely determine the required active ingredients for exerting the positive effect due to unknown dose required to elicit a response (Khan et al., 2012d). Third, the chemical composition of the plant extracts vary with different parts of the plants as well as environmental conditions, climate, soil and harvesting time (Khan et al., 2012a-d). Rajput et al. (2007) reported that the combination of an inactivated H5N1 vaccine and Cochinchina momordica seed extract as adjuvant significantly increased the daily body weight gain and immune response in broiler chickens.

HERB-BASED POULTRY GROWTH PROMOTERS

Among the major aspects of food production and safety in nowadays, reduction in the use of antibiotics and other medicinal products in the poultry production is a major concern, especially due to over bacterial resistance and possible transmission of these antibiotic residues into the human food chain (Panda et al., 2008; Sanjyal and Sapkota, 2011). Consequently, the poultry feed industry is facing increased consumer pressure to reduce the use of those antibiotic growth promoters (AGPs) in poultry diets. In broiler diets, the beneficial effects of medicinal plants and their various products including plant extracts and essential oils as phytogenic feed additives are proven (Bolukbasi and Erhan, 2007; Windisch et al., 2008; Dalkilic and Guler, 2009; Bozkurt et al., 2012b). Plant extracts and various phytobiotics that originate from leaves, roots, tubers or fruits of herbs, spices and other plants have shown to be excellent growth enhancers in poultry industry (Steiner, 2009; Wallace et al., 2010). This effect may be due to the synergistic action of various active molecules in them and the greater efficiency in the utilization of feed, resulting in enhanced growth and production (Hashemi and Davoodi, 2010). The basic strategies of including these herbs in poultry diets are to impact the metabolism by combating stress and microbial activity and there are scientific evidences to prove that herbal extracts stimulate the growth of beneficial bacteria and curtail pathogenic bacterial activity in the gastrointestinal tract of poultry. Prevention of the colonization of the pathogens and improvement of the production and activities of digestive enzymes are the essential functions of such phytogenic components (Langhout, 2000; Wenk, 2000; Lee et al., 2003, 2004; Tekeli et al., 2006; Sanjyal and Sapkota, 2011). Several strategies have been postulated to understand the growth promoting effects of herbs in poultry. First, the improved performance has been linked with increased secretion of digestive enzymes through the production of lipase, amylase, trypsin and chymotrypsin and enhanced nutrient utilization in the liver (Langhout, 2000; Khan et al., 2012d). Second, the antibacterial action of essential components of these herbs may suppress the growth of pathogenic bacteria on one hand and promote the growth of probiotic (bacillus, lactobacillus and acidophilus etc.) bacteria in the gut. No doubt literature is full of the beneficial effects of herbs in improved poultry production; however, there are many reports which negate the beneficial effects of herbs. The reason may be due to the difference in experimental protocol, environmental conditions, reduced antimicrobial effect of any plant extract through altering the substrate and unavailability of bio-ingredients which are usually absent in pure conditions (Langhout, 2000; Lee et al., 2003; Barreto et al., 2008). According to some author, the improved performance may be attributed to the essential components which have antimicrobial, antioxidant and antifungal effects (Khan et al., 2012a). Another hypothesis suggests that commercial products of a herb may exert different effects. For example, raw garlic (allicin rich( and processed garlic (non-allicin rich( differ in term of active ingredients which may potentially elicit different response in the host (Khan et al., 2012b).

Herbs which are proven as excellent growth promoters in poultry includes Withania somnifera, Ocimum sanctum, Emblica officinalis, Aloe vera, Thymus vulgaris, Curcuma longa, Origanum vulgare, Allium sativum, horseradish, cyenne pepper, ginger, anis, onions, fenugreek, cumin etc. Herbs like alfa alfa (Medicago sativa), senna (Alexandrian senna), corn flower (Centaurea cyanus) and absinthe (Artemisia absinthium) when used as feed additives in broilers can also act as efficient as well as safe growth enhancers and thereby meet the demand of the poultry industry (Dharma and Tomar, 2007; Soltan et al., 2008; Khaligh et al., 2011; Mirzaei-Aghsaghali, 2012; Kumar et al., 2013b). Most of these herbs initiate activity in the feed as flavor enhancers, stimulators of digestive secretions and total feed intake etc. They enhance the digestion and absorption of lipids through the synthesis of bile in the liver. They also accelerate the digestion and reduce the time of rate of passage through the digestive tract. Herbal growth promoters also include spices like cinnamon, cardamom, cloves, laurel, mint etc. (Frankicet al., 2009; Alsaht et al., 2014). These are well-known for their appetite stimulant effect, especially through the stimulation of pancreatic and other digestive enzymes but different herbs affect digestion processes differently, due to the wide variety of active components present in them (Frankic et al., 2009; Mirzaei-Aghsaghali, 2012). Herbs can act as alternative to Antibiotic Growth Promoters (AGPs) because they exhibit antimicrobial properties and thus can form integral part of poultry nutrition (Gbenga et al., 2009). Broad antimicrobial activity is possessed by many herbs and their bio-active constituents. There exists scientific evidence that herbs and plant extracts can work by stimulating growth of microbiota and minimizing the activity of pathogens in the poultry gastro intestinal tract. In comparison to other type of dietary treatments herb like garlic (Allium sativum) when supplemented with antibiotic and thyme in broiler chick diet causes significant increase in the length of the small intestine. Significant lower concentration of E. coli is also achieved by supplementation of such combination from herbal extracts in the diet (Kamel, 2001; Tucker, 2002; Cross et al., 2003; Lewis et al., 2003; Sarica et al., 2005). A study on Aloe vera gel has shown to improve the feed efficiency, increase gizzard weight, gastro-intestinal weight as well as length by increasing the size of digestive tract and also it has been found to reduce the total count of aerobic bacteria in the gastro intestinal tract in broilers (Sinurat et al., 2003).

EFFECT OF HERBAL PREPARATIONS ON GENERAL PERFORMANCE OF POULTRY

Herbs and herbal products are easily available, low cost, abundance and incorporated in poultry feeds to enhance the body weight gain and to increase the feed efficiency. Allinson et al. (2013) reported that herbal extracts enhances the performance in poultry and increases the feed: gain and weight gain ratio by significantly decreasing the bacterial and oocsyt count. Feeding Garlic Powder (GP) to broilers enhances the performance, improves digestibility, digestive organs, Crude Protein (CP), Dry Matter (DM) and Ether Extract (EE) digestibility (Issa and Abo Omar, 2012). Tollba and Hassan (2003) demonstrated that natural feed additives such as black cumin (Niglla sativa) and garlic (Allium sativum) improves the physiological and productive performance of broiler chicks, growth rate, Feed Conversion Ratio (FCR) and decreased mortality rate under high temperature conditions. Thyme (Thymus vulgaris) and oregano (Origanum vulgare) supplementation at 15 or 20 g kg-1 diet can increase the feed conversion ratio, body weight gain, feed intake and performance of broilers due to its active principle known as carvacrol and thymol (Abdel-Wareth et al., 2012). Incorporation of essential oils from herbs in poultry diets showed various beneficial effects, enhancing performance traits, reducing pathogenic bacteria and decreasing antibiotic residues in meat and egg products (Hertrampf, 2001). Demir et al. (2003) and Elagib et al. (2013) reported that incorporation of growth promoter such as 3% of garlic (Allium sativum) powder (250 g) causes significant increase in feed intake, body weight gain, higher feed conversion ratio, highest breast weight and growth performance. Supplementation of feed with Curcuma longa rhizome powder at the rate of 0.75-1 g kg-1 results in increased feed consumption in broilers (Al-Kassie et al., 2011). Initial body weight, final body weight, egg weight and egg yolk index, egg shell thickness, egg yolk weight, plasma glucose and triglyceride were not statistically affected by dietary garlic powder supplementation (1, 2 or 4%) in laying quails for 14 weeks (Canogullari et al., 2010). On the contrary, plasma and yolk cholesterol concentrations were decreased with increasing garlic powder supplementation but the level of HDL in blood was augmented with garlic supplementation compared to the control diet. In the previous studies it was found that rabbits fed diet supplemented with Yucca schidigera extract did not affect growth performance in general but improved the immunity function, moreover, rabbits fed diet tlinesupplemented with yucca extract had lower ammonia in serum, lipid peroxidation in liver and increased hepatic antioxidant activities.

HERBS AS ANTIOXIDANTS FOR POULTRY

Nowadays, there has been an increase in demand for natural antioxidants in food due to its health benefits against oxidative stress and several diseases. Plant derived antioxidants are gaining more demand in poultry nutrition because their meat has high content of polyunsaturated fatty acids and susceptible to lipid oxidation (Christaki, 2012). Many plants have been identified as excellent poultry antioxidants; important among which are rosemary (Rosmarinus officinalis), Olive leaves (Olea europea L.) garden thyme (Thymus vulgaris), marjoram (Origanum majorana), sage (Salvia officinalis), oregano (Origanum vulgare) and so forth (Madsen and Bertelsen, 1995; Botsoglou et al., 2002, 2005, 2013; Rahal et al., 2014b). Among these, Rosemary and rosemary extracts are some of the most studied natural antioxidants in poultry products and these studies have demonstrated the ability of rosemary products to act as natural antioxidants in various poultry products (Rojas and Brewer, 2007; Karre et al., 2013). Apart from these, fruits like plum, grape seed extract, cranberry, pomegranate, bearberry, pine bark extract etc. provide good alternatives to synthetic antioxidants due to the high phenolic compound in them (Brannan, 2008; Karre et al., 2013). Spices like cinnamon, cloves, marjoram, wild marjoram, caraway, peppermint, nutmeg etc., have been shown to have antioxidant properties as they contain the compounds such as polyphenolics, lignans, flavonoids and terpenoids (Craig, 1999; Botsoglou et al., 2013). Among the herbal plants, tulsi (Ocimum sanctum) and Ashwagandha (Withania somnifera) have been proven as an excellent adaptogen and antistress agent. It has proven to reverse the Cadmium-induced oxidative stress in chicken (Bharavi et al., 2010). Studies showed that active ingredients of plants have strong antioxidant effects including neutralization of superoxide, hydrogen peroxide and nitric oxide either by scavenging radicals or by increasing the production of catalase (CAT), superoxide dismutase (SOD) and glutathtion peroxidase (GPx) (Ali et al., 2006; Yarru et al., 2009). Turmeric has been shown to increase the expression of SOD gene and protects the mitochondria against premature damage (Reddy and Lokesh, 1994; Miquel et al., 2006). The beneficial antioxidant effect of turmeric has been due to the presence of tetrahydro curcumin, cinnamic acid, curlone and niacin (Khan et al ., 2012a). Ginger contains some important metabolites and alkaloids like gingerol, shogaol, gingerdione, shogaols and other phenolic compounds which have antioxidant properties (Zhang et al., 2009; Zhao et al., 2011). In thyme, important alkaloids isolated include carvacrol, thymol, caffeic acid, p-cymene-2, 3-diol and biphenylic (Schwarz et al., 1996; Bolukbasi et al., 2006). Regarding the mechanism of action of thymol, Lee et al. (2004) concluded that phenolic OH group of thymol acts as hydrogen donor to neutralize the peroxyl radicals which is produced during the initial step of lipid peroxidation.

EFFECT OF HERBAL PREPARATION ON ENZYMES OF POULTRY

Deshpande (2006) reported that dietary supplementation of tulsi leaf powder (Ocimum sanctum) causes significant increase in serum cholesterol and HDL levels in laying hens. However, turmeric (Curcuma longa) as nutraceutical to improve broiler performance had no significant effect on cholesterol concentration (Namagirilakshmi, 2005). Supplementation of turmeric rhizome powder to broilers considerably reduced the liver enzymes such as ALT and ALP (Emadi and Kermanshahi, 2007) and tulsi leaf powder ameliorates the lead induced toxicity in cockerels by reducing the liver enzymes (Prakash et al., 2009). Feeding of tulsi leaf powder to broilers, neutralises the toxic effects of aflatoxins by significantly reducing the enzyme activities of AST, ALT and ALP (Sapcota and Upadhyaya, 2009). Lanjewar et al. (2008) reported that supplementation of tulsi leaf powder to broilers causes significant reduction in serum LDL cholesterol, total cholesterol and triglycerides. However, Gupta and Charan (2007) reported that tulsi supplementation reduces serum SGOT levels in broilers, whereas it has no significant effect on SGPT, creatinine and uric acid. Supplementation of herbal growth promoters such as amla to broilers causes reduced cholesterol, increased SAP and SGPT levels and no effect on SGOT (Vidyarthi et al., 2008). Reddy et al. (2007) reported that feeding of broilers with tulsi leaf powder (0.5%) and selenium (0.3 ppm) significantly decreased the lipid peroxidation levels and increased the plasma GSH levels. Feeding of broilers with combination of Aloe vera and Curcuma longa had no significant effect on serum glucose, HDL, LDL, total cholesterol and triglyceride levels. Furthermore, Reddy (2010) observed that supplementation of amla, tulsi and turmeric powder in different combinations had no significant change on serum SGOT, SGPT and cholesterol levels.

ROLE OF HERBS IN ORGANIC EGG PRODUCTION IN POULTRY

Recently, organic egg production is gaining more importance and needs access to forage material such as pasture/crop in the hen yard or supplemented with roughage in the form of silages and vegetables in addition to the basal diet (The Council of the European Union, 2007). Hammershoj and Steenfeldt (2012) studied the effect of feeding kale (Brassica oleracea ssp. acephala), thyme (Thymus vulgaris) and basil (Ocimum basilicum) as a forage material on various egg quality parameters and egg production. They reported no significant difference in forage intake and laying rate between treatment groups but kale treatment significantly increased egg weight, higher egg shell strength; lutein, β-carotene and violaxanthin content. Several studies have emphasized on the importance of forage material (whole wheat, Phacelia tanacetifolia, Fagopyrum esculentum and Linum usitatissimum) on egg production, calcium supplements to laying hens, carotenoids in egg yolk, various egg quality parameters, conversion of oil rich forage material into specific fatty acids to the egg yolk and supply of vitamins, essential amino acids and minerals (Horsted et al., 2006; Hammershoj and Steenfeldt, 2009; Woods and Fearon, 2009; Hammershoj et al., 2010). Moreover, different aromatic herbs, vegetables and forage material can directly transfer flavours to the egg (Tserveni-Gousi, 2001) and as a result of altered microflora composition of the intestine due to change in forage material, thereby causing new flavours to the egg (Richter et al., 2002).

ROLE OF HERBS IN ORGANIC MEAT PRODUCTION IN POULTRY

Incorporation of turmeric (Curcuma longa) root powder and mannan oligosaccharides in broiler ration as a feed supplement results in decrease in the fat percentage up to 1% (Al-Sultan, 2003) and 1.2% (Samarasinghe et al., 2003) levels over body weights. Emadi and Kermanshahi (2006) reported that supplementation of turmeric rhizome powder (0.75%) in broiler rations leads to improved carcass quality, lean meat and significant decrease in abdominal fat pad up to 57% level and heart weights to live body weight. Furthermore, turmeric powder supplementation in broiler feed causes higher dressing percent up to 57% level, increased the liver weight, spleen weight and whole giblets weight (Kurkure et al., 2002; Al-Sultan, 2003; Durrani et al., 2006). Shyama Tulsi (Ocimum sanctum) leaf preparation as a broiler feed supplementation for its growth promoter activity causes no significant change in the weights of the bursa, liver and spleen (Gupta and Charan, 2007). Singh et al. (2007b) reported that supplementation of the amla and turmeric combined powder at the rate of 5g kg-1 in broiler feed results in enhanced dressing percentage and decreased mortality in broiler chicks. Mehala and Moorthy (2008) demonstrated that combination of Curcuma longa (Turmeric) and Aloe vera at different concentrations showed no significant change in the abdominal fat and breast muscle weights. A combination of tulsi, amla and turmeric at the rate of 0.5% has not shown significant difference in ready to cook yield percentage and giblet weights (Reddy, 2010).

CONCLUSION

It has been vivid that the potential of medicinal herbs as the valuable source of therapeutics aids has attained a global significant place in the health system all over the world not only for humans but also for animals as well as birds. Herbs can be used as a good alternative therapeutic aid to costly allopathic medicines/chemotherapy and boosting immune functions in intoxicated conditions and can also effectively complement allopathic medicines in diseased state. Globally, the poultry industry is going through a crucial era of increasing demand for the products at the same time, experiencing production and health problems. So the sustainable present and future of poultry sector necessitates the optimum and accurate implementation of herbal remedies which overcome the demerits of extensive allopathic drugs. The tremendous potentials of traditional, herbal, botanical and medicinal plants could be made practical with the adjunct of the recent advances in science and technologies including of molecular, biotechnological and nanotechnology. Also, there is a great need to strengthen Research and Developmental facilities for integration of these modern and novel scientific advances with herbal usages. A thorough re-evaluation and scientific validation of these valuable ancient medicines need to be redirected from current perspectives and future prospects which are in great demand in the developed world as they are able to cure many infectious diseases. These need to be much promoted to combat a variety of poultry diseases, particularly the immunosuppressive ones, safeguard poultry health and boost the productive performance of birds.

Research works and project formulations should be carried out for studying and assessing the potentials of useful medicinal properties, discovering beneficial active components, revealing mechanism of actions of individual herbs in particular, herbal metabolites and standardization of doses, purification and extracting procedures, so as to authenticate, strengthen and widen the beneficial usages of these traditional medicines. Advances in biotechnological and molecular approaches being exploited for allopathic drugs and other medicines need to be explored to their full potentials for scientific validation and promoting fruitful applications of herbs. Nanotechnology based ‘smart’ drug delivery systems and nanomedicines would facilitate drug delivery in an efficient way and targeted manner which would reduce the drug doses to be administered as well as drug toxicity/side effects thereby rendering safer products. Species identification, cultivation and efforts for conserving precious herbal species also need to be taken on priority. Apart from this, strict quality control and regulatory measures need to be implemented so as to have a check on the standards and avoid adulteration of these various traditional medicines/products available. All these approaches would help to prove the medicinal and health values of herbs and their products which would make them promoted and popularized as well as accepted by mass community with dimension and practical applications for animal and human health benefits as well as poultry industry. These will all together improve prospects of this traditional wealth towards modern medicines, drugs and health care products derived from their origin to improve the market potential and commercialization aspects at global level.

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