Application of herbs and phytogenic feed additives in poultry production-A Review

INTRODUCTION

The industrialization of poultry husbandry and the improvement of feed nutritional efficiency have accelerated the introduction of feed additives which became widely used in animal feed for many decades. The objective outlined by scientists, is to increase production (eggs, meat) while maintaining animals in good health. The use of antibiotics in poultry feed as a growth promoter is beneficial in improvement of production parameters and diseases prevention. However this large utilization has led to the increasing resistance of pathogens to antibiotics and the accumulation of antibiotic residues in animal products and in the environment. This situation requires the world to restrict using AGPs in animal feed (Nisha, 2008).

The nutritional value of raw materials available to livestock is closely linked to the quality and size of the microbial flora especially in the host animal digestive tract and its environment. Unlike ruminants, poultry do not have a natural bacterial flora capable of degrading all nutrients. These animals are characterized by a resistor and a limited immunity against infection due to colonization by pathogenic microorganisms. This is why, the use of AGPs for the inhibition of pathogenic bacteria has been recommended in order to improve production performance and animal health. Nevertheless, this is no longer possible after the observation made by the WHO on antimicrobial resistance in both animals and humans. From 2006, the European Union banned systematically the use of AGPs in animal feed (http://www.efsa.europa.eu/en/topics/topic/amr.htm).

The removal of AGPs from animal feed may affect their productions performance and foster the resurgence of pathogens causing illness and economic losses in farms.

In this context, herbs and plant extracts are searched to be incorporated in poultry feed as growth promoters such as probiotics and prebiotics (Alloui, 2013).

Herbs and plant extracts represent a new class of additives in poultry feed. Their uses are still limited in relation to their mode of action and aspects of application. In addition, complications may be encountered due to various changes in botanical origins, transformations and compositions of plants and their extracts. Most of the investigations have studied the interactions of various active compounds and their physiological impacts and effects on production performance (Figueiredo et al., 2008)

The hypothesis that phytogenic compounds could improve the food palatability has not been demonstrated. Furthermore, it is believed that the phytogenic compounds can improve the digestive enzyme activity and nutrient absorption. Many studies have demonstrated their antioxidant and antimicrobial activity in vitro but in vivo these results are limited.

In addition, other effects such as anti-inflammatory, anti-fungal, anti-infectious and antitoxigenic have been confirmed in some researches (Giannenas et al., 2003; 2004; Lopez - Bote, 2004; Burt, 2004; Lee et al., 2004; Walace, 2005; Naidoo et al., 2008; Ayachi et al., 2009; Arczewska-Wlosek and Swiatkiewicz , 2012; Ahmed et al., 2013; Khan, 2014 ).

All these assumptions are being addressed by the project ‘’REPLACE’’ in the EU programs framework. The objective of this project is to examine the possibility of using plants and their extracts as natural alternatives to antimicrobials in animal feed (http://www.replace-eu.com). The aim of this work is to provide a synthesis of current knowledge in the scientific literature demonstrating the efficiency of plants or their extracts, to replace AGPs in poultry feed.

Definition and regulation of phytogenics feed additives (PFA)

Herbs and plant extracts used in animal feed, called today phytogenics feed additives (PFA), are defined as compounds of plant origin incorporated into animal feed to enhance livestock productivity through the improvement of digestibility, nutrient absorption and elimination of pathogens residents in the animal gut ( Kamel, 2001; Balunas and Kinghorn, 2005; Athanasiadou et al., 2007) .

The large variety of plant compounds used as PFA are assembled according to their origin and treatment, such as herbs and spices (eg: garlic, anise, cinnamon, coriander, oregano, chili, pepper, rosemary and thyme) but also essential oils or oleoresins (Kamel, 2000). Another category of compounds are extracted exclusively from fruits. They are represented by water soluble polyphenols (flavonoids) which can also be used in animal feed (Lopez –Bote, 2004). The content of active substances in these products can vary greatly depending on what part of the plant is used (grains, leaves, roots, bark, flowers, or buds), the harvest season and geographical origin. The technique of treatment (cold, steam distillation, extraction or maceration with non-aqueous solvents…) also changes the active substances and related compounds in the final product (Windisch et al., 2008).

The use of feed additives is generally subjected to regulatory restrictions. In general, they are considered as products applied by the farmer to healthy animals for nutritional purposes on a permanent basis, in contrast with veterinary drugs which are applied for the prophylaxis and treatment of diagnosed diseases under veterinary supervision for a limited time followed by a waiting period.

In the EU, these feed additives must demonstrate the identity and traceability of the entire commercial product, the claimed nutritional effects in addition to proofs of absence of interaction with other compounds. They must be tolerated by the animals, the users (farmers, manufacturers of animal feed) and the environment (European Commission, 2003).

Problems using these plant extracts in animal feed may occur and cause physiological disturbances in animals, in relation with biochemical interactions within the animal organism. This is why the study of their use in diets will focus not only on their antioxidant, antimicrobial activities and their beneficial effects on palatability and intestinal functions, but also on their effectiveness to promote animal growth as AGPs.

Antioxidant action of PFA

The antioxidant properties of herbs and spices have been largely described by Craig (1999), Nakatani (2000) , Lambert et al., (2001) ; Ruberto et al., (2002) ; Wei and Shibamoto (2007). Among the varieties of plants with antioxidant constituents, plants of the Labiatae families (like mint) have attracted a great interest. Their antioxidative activities are due to phenolic terpenes (Cuppett and Hall, 1998). Other herbs species with antioxidative properties such as thyme and oregano contain large amounts of monoterpenes, thymol and carvacrol (Ruberto et al., 2002; Rahim et al., 2011). Plants rich with flavonoids such as green tea and other Chinese herbs have been described as natural antioxidant (Nakatani, 2000; Piao et al., 2006; Wei and Shibamoto, 2007).

Black pepper (Piper nigrum), red pepper (Capsicum annuum L) and chili (Capsicum fretuscene) contain also several antioxidative compounds (Nakatani, 1994) but in many of these plants, the parts containing the active substances are of a very fragrant and/or spicy taste leading to restrictions of their use in animal feed.

The antioxidant properties of several PFA can contribute to dietary lipids protection from oxidation. This aspect has not been described in poultry feed; however Labiatae plants used as antioxidants in feed diet of small animals is very encouraging (Cuppett and Hall, 1998).

The activity of Labiatae phenolic compounds in improving the stability of animal products has been demonstrated in broiler chickens by several authors (Botsoglou et al., 2002a; Botsoglou et al., 2003; Basmacioglu et al., 2004; Giannenas et al., 2005; Florou - Paneri et al., 2006). The oxidative stability was also demonstrated with other PFA (Botsoglou et al., 2004; Govaris et al., 2004; Schiavone et al., 2007). However, it is uncertain whether these phytogenics antioxidants can replace commonly used antioxidants in feeds (α - tocopherol) in common feeding practices.

The use of PFA as an antioxidant is not only important for the poultry health, but also for the oxidative stability of their products (meat). Supplementation of turkey feed with 200 mg extract of oregano / kg feed significantly decreases lipid per-oxidation during refrigerated storage of fresh and cooked meat (Botsoglou et al., 2003).

The use of PFA instead of antioxidants is costly. However, this economic impact can be reduced by intensifying systemic needed plants and developing new technological processes of extraction.

Actions on palatability and digestion of FPA

Some PFA were sometimes seen as having a role to improve the taste and feed palatability. This implies an improvement in poultry production performance. The number of studies that tested the effect of plant extracts on palatability is very limited in this specie.

In general, an increase in feed intake in chickens is much more due to additives such as organic acids, probiotics and prebiotics (Catala - Gregori et al., 2007). Thus, the assumption that herbs, spices and extracts improve the feed palatability does not seem to be justified in general (Windisch et al., 2008).

A wide range of PFA is known to exert beneficial actions on the gastrointestinal tract, such as spasmolytic, laxative or against flatulence (Chrubasik et al., 2005). In Chinese medicine, cinnamon (Cinnamonum cassia zeylanicum) was used against diarrhea and reduced appetite. Smith-Palmer et al., (1998) found cinnamon extract, thyme and clove to be efficient against several bacteria. Furthermore, stimulation of the digestive secretions of bile, mucus, saliva and improvement of enzymes activities are of great nutritional interest (Platel and Srinivasan, 2004).

Other researchers have shown that essential oils used in chickens have positively influenced the activity of trypsin and amylase (Lee et al., 2003; Jang et al., 2004; Jamroz et al., 2005). It was also found that the phytogenic additives have a stimulatory effect on intestinal mucus in chickens. This effect is assumed to influence the adhesion of pathogens and in consequence help to stabilize the microbial equilibrium in the chicken gut (Jamroz et al., 2006).

These improvements could also be due to morphological changes induced in the gut such as villi and crypts size modifications in the jejunum and colon of PFA ingesting chickens (Jamroz et al., 2006).

Srivastava et al., (1995); Kumar and Berwal, (1998) showed that the use of garlic oil (Allium sativum) have anti-tumoral and anti-oxidative properties. Similarly, a British study showed a positive effect of garlic on growth and feed intake in chickens (Lewis et al., 2003). These authors concluded that garlic may have a positive effect on the gut flora by reducing pathogenic bacteria explaining the improved chicken performances.

All these observations encourage the assumption that these additives may favorably affect the gut functions, but the number of in vivo studies in poultry is still limited.

Antimicrobial and immune actions of FPA

PFA are well known for their antimicrobial effects in vitro against important pathogens but also against fungi (Allen et al., 1997; Smith -Palmer et al., 1998; Cosentino et al., 1999; Waldenstedt, 1998, 2003; Giannenas and Kyriazakis, 2009).

Most studies show a greater sensitivity of Gram + bacteria compared to Gram- (Shelef, 1983; Zaika, 1988; Smith -Palmer et al., 1998; Ceylan and Fung, 2004). This does not mean that the plant extracts are not active on Gram - bacteria, but the dosage should be higher. In addition, the antimicrobial activity is dependent on the physico-chemical characteristics of plant compounds and bacterial strains used (Sari et al., 2006). Burt and Reindeers (2003) observed an antibacterial effect of essential oils of oregano and thyme against E. coli (Gram -) at a dose of 0.6 ml / L.

Ayachi et al., (2009) studied the in vitro effect of some extracts of berries, dates and thyme to fight against E. coli and Salmonella isolates from chicken. These authors concluded that only the thyme would be effective against Salmonella.

Thyme would work with the most active compounds (thymol and carvacrol) against fungi such as Candida albicans (Cosentino et al., 1999). Other investigations have demonstrated the effectiveness of walnut leaves (Juglandaceae) to reduce the proliferation of Clostridium perfrengens in chickens but also to enhance the growth of these birds (Lovland and Kaldhusdal, 2001 ; Engberg et al., 2007; Mathis et al., 2007). Clove frequently used as a spice is very rich in eugenol. It is used as an antibacterial in human and veterinary medicine (Nascimento et al., 2000; Rhayour et al., 2003).

The essential oil of oregano contains about 60% carvacrol and 10% thymol with a demonstrated effectiveness against some strains of salmonella (Koscova et al., 2006) located in the digestive tract of chicken. However, to have a good efficacy against several types of microorganisms, it is interesting to combine several extracts devoid of chemical incompatibility. The same way as antibiotics, antibacterials from plants do not distinguish between commensal and pathogenic bacteria. It is worth-noting that, as other bacteria, the lactobacilli and bifidobacteria are less sensitive to plant extracts, which is reassuring, because they are used as probiotics.

PFA are an interesting solution to clean the digestive tract of birds which is very useful in diseases prevention in poultry (Shelef, 1983). Additionally, some plant extracts have demonstrated an activity against some chicken parasites, especially coccidia (Eimeria spp) (Giannenas et al., 2003, 2004; Christakis et al., 2004; Naidoo et al., 2008; Rczewska-Wlosek and Swiatkiewicz, 2012).

Betaine is a byproduct of the sugar beet industry; it has recently been a subject of several studies in the USA and Sweden. It seems to have a positive impact in fighting coccidiosis. In Sweden, Waldenstedt et al., (1999) showed that the addition of betaine in the poultry feed, reduced weight loss during coccidial infection by different Eimeria species in poultry. It protects against osmotic stress associated with dehydration and permits normal metabolic activity of cells. However, the protective effects of betaine on the intestinal cells are also exerted on parasitic cells.

Turmeric is a spice coming from the rhizome of Curcuma longa. It is used as a food coloring, but also for medicinal purposes. The active component is curcumin, a phenolic compound at concentrations of about 1 to 5%. It has antioxidant, anti-inflammatory and antitumoral activities. In infected chicken with Eimeria maxima, supplementation of feed with 1% turmeric spice improves weight gain, reduces intestinal lesions and oocyst excretion. Curcumin exerts its anticoccidial effect through its antioxidant action on the immune system (Allen et al., 1998). Soltan et al., (2008) found that the supplementation of poultry feed with anise grains, improved blood parameters and increased the phagocytic activity and lymphocyte counts. Cinnamon has also an immuno-stimulating effect that can be attributed to its anti-oxidant property.

In addition to all these antimicrobial implications, phytogenics improve the microbial carcass hygiene and the preservation quality, in relation with their antimicrobial and antioxidant properties (Botsoglu et al., 2002b; Ruberto et al., 2002; Aksit et al., 2006).

According to the European Food Safety Authority (EFSA), this alternative should be considered as one of the most effective ways to reduce the microbial contamination of food and to control the spread of foodborne diseases within the human population through the food chain. Addition of plants extracts in foods and / or systems used on carcass surfaces decreases the bacterial contamination of poultry products (Gülmez et al., 2006). In the improvement of microbial carcass hygiene, oils extracted from plants (such as oregano, rosemary, sage) have a positive effect (Young et al., 2003; Govaris et al., 2007). However, it is too early to conclude that these decontamination methods are entirely effective and reliable.

Effects of FPA on production performances

The effects of FPA on production performance have shown promising results. Cabuk et al., (2006) measured production parameters in chickens grown on feed supplemented with a mixture of essential oils of oregano, bay leaf, sage, anise and citrus. This mixture has significantly improved feed conversion resulting of high nutrients availability due to changes in the intestinal ecosystem.

Lippens et al., (2005) have attempted to assess the effectiveness of a mixture composed of cinnamon, oregano, thyme, cayenne pepper, citrus extracts and of another mixture of plant extracts and organic acids in comparison with the avilamicine in chicken feed. The supplemented with plant extracts group of animals reached a much larger body weight than the other groups. Apparently, the increase in body weight was due to the increase of feed intake. This was attested by a reduced feed conversion in animals of the plant extracts group (0.4% lower than avilamicine group and 2.9% lower than the organic acids group).

Fenugreek (Trigonella foenum-graecum), is an annual legume, cultivated all over the world, it is one of the herbs with multi-functional characteristics. It is a good source of dietary proteins for humans and animals. Fenugreek seeds supplementation improved significantly feed conversion ratio of broiler chickens which might be related to morphological changes in the gastrointestinal tissues (Srinivasan, 2006; Alloui et al., 2012; Mamoun et al., 2014).

The inclusion of anise seeds at a level of 0.5-0.75/kg corn-soybean-meal diet administered to broilers during 6 weeks, improved their body weight gain, performance index and relative growth rate. In contrast, a higher inclusion level of anise seeds (1.5 g/kg diet) reduced growth performance (Soltan et al., 2008).

Garlic (Allium sativum), thyme (Thymus vulgarus) and conflower (Echinacea purpurea) as feed supplements have recently been reported to exert a wide range of beneficial effects on the production performance (weight gain, feed conversion, egg production and quality) of broilers and laying hens (Aji et al., 2011; Rahimi et al., 2011; Khan et al., 2012).

Bolukbasi and Erhan, (2007) studied the effect of dietary supplementation with thyme on performance of laying hens and E. coli concentrations in their feces. Thyme addition to basal diet at the level of 0.1-0.5% have given an improvement in feed conversion and egg production associated to a decline of E.coli concentration in feces.

Effect of PFA on egg quality traits, such as yolk composition, shell thickness or Haugh Unit rating, were reported in a few studies only, whereas the majority of reports did not identify substantial effects (Nichol and Steiner, 2008; Singh, 2009; Navid et al., 2013 ).

CONCLUSION

PFAs are good alternatives to replace AGPs. They can be combined with other compounds such as prebiotics or probiotics to promote the performance of poultry production. Phytogenics have been used since a very long time, but empirically. General mechanisms of action were little known in humans and animals. Nowadays, much progress has been made to evaluate their effects on the poultry organism. For this, it is the responsibility of additivemanufacturers to promote and control these products taking into consideration all legislative requirements governing the production and marketing of these products. The identification, composition, effectiveness, toxicity and residues analysis, traceability and the risk of manipulation are the main factors to control during the manufacturing process. The industry of animal feeds and especially the poultry one must bring to market an effective, cheap diet of high quality.

REFERENCE

Ahmed, A., R. Mangaiyarkarasi, N. Shahid Umar Shahina, S. Rahmanullah and Y. Zahra. 2013. Effect of black tea extract (polyphenols) on performance of broilers. Int. J. Adv. Res. 1 (7): 563-566

Aji, S.B., K. Ignatuius, A.Y. Ado, J.B. Nuhu and A. Abdulkarim. 2011. Effect of feeding onion (Allium cepa) and garlic (Allium sativum) on some performance characteristics of broiler chickens. Res. J. Poult. Sci. 4: 22-27.

Aksit, M., E. Goksoy, F. Kok, D. Ozdemir and M. Ozdogan. 2006. The impacts of organic acid and essential oil supplementations to diets on the microbiological quality of chicken carcasses. Arch. Geflugelkd. 70:168-173.

Allen, P.C., H.D. Danforth and P.C. Augustine. 1998. Dietary modulation of avian coccidiosis. Int. J. Parasitol. 28: 1131-1140.

Allen, P.C., J. Lydon and H.D. Danforth. 1997. Effects of components of Artemisia annua on coccidian infections in chickens. Poult. Sci. 76 (8):1156-1163.

Alloui, M.N., W. Szczurek and S. Swiatkiewicz. 2013. The usefulness of prebiotics and probiotics in modern poultry nutrition. Ann. Anim. Sci. 13 (1): 17–32

Alloui, N., S. Ben Aksa and M.N. Alloui. 2012. Utilization of fenugreek (Trigonella foenum-graecum) as growth promoter for broiler chickens. J. World Poult. Res. 2(2): 25-27.

Arczewska-Wlosek A. and S. Swiatkiewicz. 2012. The effect of a dietary herbal extract blend on the performance of broilers challenged with Eimeria oocysts. J. Anim. Feed Sci. 21: 133- 142.

Athanasiadou, S., J. Githiori and I. Kyriazakis. 2007. Medicinal plants for helminthes parasite control: facts and fiction. Animal. 1 (9):1392–1400.

Ayachi, A., N. Alloui, O. Bennoune, S. Yakhlef, W. Daas Amiour, S.Bouzdi, K. Djemai Zoughlache, K. Boudjellal and H. Abdessemed. 2009. Antibacterial activity of some fruits; berries and medicinal herb extracts against poultry strains of Salmonella. Am. Eurasian J. Agric. Environ. Sci. 6 (1):12-15

Balunas, M.J. and A.D. Kinghorn. 2005. Drug discovery from medicinal plants. Life Sci. 78(5):431-441

Basmacioglu, H., O.Tokusoglu and M. Ergul. 2004. The effect of oregano and rosemary essential oils or alpha-tocopheryl acetate on performance and lipid oxidation of meat enriched with n-3 PUFAs in broilers. S. Afr. J. Anim. Sci. 34:197–210.

Bölükbasi, S.C. and M.K. Erhan. 2007. Effect of dietary thyme (Thymus vulgaris) on laying hens performance and E. coli concentration in feces. Int. J. Nat. Eng. Sci. 1(2): 55-58

Botsoglou, N.A., P. Florou-Paneri, E. Christaki, D.J. Fletouris and A.B. Spais, 2002a: Effect of dietary oregano essential oil on performance of chickens and on ironinduced lipid oxidation of breast, thigh and abdominal fat tissues. Br. Poult. Sci. 43: 223–230.

Botsoglou, N.A., P. Florou-Paneri, E. Christaki, D.J. Fletouris and A.B. SPAIS. 2002b. Effect of dietary oregano essential oil on lipid oxidation in raw and cooked chicken during refrigerated storage. Meat Sci. 62: 259-265.

Botsoglou, N.A., S.H. Grigoropoulou, E. Botsoglou, A. Govaris and G. Papageorgiou. 2003. The effects of dietary oregano essential oil and [alpha]-tocopheryl acetate on lipid oxidation in raw and cooked turkey during refrigerated storage. Meat Sci. 65: 1193–1200.

Botsoglou, N. A., E. Christaki, P. Florou-Paneri, I. Giannenas, G. Papageorgiou and A.B. Spais. 2004. The effect of a mixture of herbal essential oils or alpha-tocopheryl acetate on performance parameters and oxidation of body lipid in broilers. S. Afr. J. Anim. Sci. 34: 52–61.

Burt, S. 2004. Essential oils: their antibacterial properties and potential applications in foods – a review. Inter. J. Food Microbiol. 94: 223- 253

Burt, S. and R.D. Reindeers. 2003. Antibacterial activity of selected plant essential oils against E. coli O157:H7. Lett. Appl. Microbiol. 36 (3):162-167.

Cabuk M., M. Bozkurt, A. Alçiçek, K. Akba and Y. Küçükylmaz. 2006. Effect of an herbal essential oil mixture on growth and internal organ weight of broilers from young and old breeder flocks. S. Afr. J. Anim. Sci. 36: 135– 141.

Catala-Gregori, P., S. Mallet, A. Travel and M. Lessire. 2007. Un extrait de plante et un probiotique sont aussi efficaces que l’avilamycine pour améliorer les performances du poulet de chair. VIIemeJournées de la Recherche Avicole, Tours, France, 202-206.

Ceylan, E. and D.Y.C. Fung. 2004. Antimicrobial activity of spices. J. Rapid Methods Autom. Microbiol. 12 (1):1-55.

Christaki, E., P. Florou-Paneri, I. Giannenas, M. A. Papazahariadou, N. A. Botsoglou and A.B. Spais. 2004. Effect of a mixture of herbal extracts on broiler chickens infected with Eimeria tenella. Anim. Res. 53: 137–144.

Chrubasik, S., M.H. Pittler and B.D. Roufogalis. 2005. Zingiberis rhizome: A comprehensive review on the ginger effect and efficacy profiles. Phytomedicine. 12: 684–701.

Cosentino, S, C.I.G. Tuberoso, B. Pisano, M. Satta, V. Mascia and F. Palmas. 1999. In vitro antimicrobial activity and chemical composition of Sardinian thymus essential oils. Lett. Appl. Microbiol. 29: 130-135.

Craig, W.J. 1999. Health promoting properties of common herbs. Am. J. Clin. Nutr. 70 (Suppl.): 491–499.

Cuppett, S.L. and C.A. Hall. 1998. Antioxidant activity of Labiatae. Adv. Food. Nutr. Res. 42: 245–271.

Engberg, R.M., B.B. Jensen and O. Hojberg. 2007. Plant of the Juglandaceae family as alternative to antibiotic growth promoters in broiler production. 16th European Symposium on Poultry Nutrition, Strasbourg, France.

European Commission. 2003. Regulation (EC) N 1831/2003 of the European Parliament and of the Council of 22 September 2003 on additives for use in animal nutrition. Official EU Journal.

Figueiredo, A.C, J.G. Barroso, L.G. Pedro and J.J.C. Scheffer 2008. Factors affecting secondary metabolite production in plants. Flavour Fra. J. 23: 213-226

Florou-Paneri, P., I. Giannenas, E. Christaki, A. Govaris and N.A. Botsoglou. 2006. Performance of chickens and oxidative stability of the produced meat as affected by feed supplementation with oregano, vitamin C, vitamin E and their combinations. Arch. Geflugelkd. 70: 232–240.

Giannenas, I.A., P. Florou-Paneri, N.A. Botsoglou, E. Christaki and A.B. SPAIS. 2005. Effect of supplementing feed with oregano and (or) alpha-tocopheryl acetate on growth of broiler chickens and oxidative stability of meat. J. Anim. Feed Sci. 14:521–535

Giannenas, I.A. and I. Kyriazakis. 2009. Phytobased Products for the control of intestinal diseases in chickens in the post antibiotic era. Phytogenics in animal nutrition: Natural concepts to optimize gut health and performance: Ed. Nottingham University Press, ISBN 978-1-904761-71-6, 61-85.

Giannenas, I., P. Florou-Paneri, M. Papazahariadou, E. Christaki, N.A. Botsoglou and A.B. Spais. 2003. Effect of dietary supplementation with oregano essential oil on performance of broilers after experimental infection with Eimeria tenella. Arch. Anim. Nutr. 57: 99-106.

Giannenas, I., P. Florou-Paneri, M. Papazahariadou, E. Christaki, N.A. Botsoglou and A.B Spais. 2004. Effect of diet suplementation with ground oregano on performance of broiler chickens challenged with Emeria tenella. Arch. Geflugelkd. 68: 247-252.

Govaris, A , N.A. Botsoglou , G. Papageorgiou, E. Botsoglou and I. Ambrosiadis. 2004. Dietary versus post-mortem use of oregano oil and/or alpha-tocophenol in turkeys to inhibit development of lipid oxidation in meat during refrigerated storage. Int. J. Food. Sci. Nutr. 55: 115-123.

Govaris, A, P. Florou Panieri, E. Botsoglou, I. Giannenas, I. Ambrosiadis and N.A. Botsoglou. 2007. The inhibitory potential of feed supplementation with rosemary and/or– tocopheryl acetate on microbial growth and lipid oxidation of turkey breast during refrigerated storage. LWT. Food Sci. Tech. 40: 331-337.

Gulmez, M., N. Oral and L. Vatansever. 2006. The effect of water extract of sumac (Rhus coriaria L.) and lactic acid on decontamination and shelf life of raw broiler wings. Poult. Sci. 85: 1466-1471.

Jamroz D., T. Wertelecki, M. Houszka and C. Kamel. 2006. Influence of diet type on the inclusion of plant origin active substances on morphological and histochemical characteristics of the stomach and jejunum walls in chicken. J. Anim. Physiol. Anim. Nutr. 90: 255–268.

Jamroz, D., A. Wiliczkiewicz, T. Wertelecki, J. Orda and J. Scorupinska. 2005. Use of active substances of plant origin in chicken diets based on maize and domestic grains. Br. Poult. Sci. 46: 485-493.

Jang I.S., Y.H. Ko, H. Y. Yang, J. S. Ha, J.Y. Kim, S.Y. Kang, D. H. Yoo, D.S. Nam, D. H. Kim and C.Y. Lee. 2004. Influence of essential oil components on growth performance and the functional activity of the pancreas and small intestine in broiler chickens. Asian. Australas. J. Anim. Sci. 17: 394–400.

Kamel, C. 2000. A novel look at a classic approach of plant extracts. Feed Mix. 11: 19-21. Kamel, C. 2001. Natural plant extracts: classical remedies bring modern animal production solutions. Feed manufacturing in the Mediterranean region. Improving safety: from feed to food. In Brufau J. (Ed.) Zaragoza: CIHEAM-IAMZ, 31-38.

Khan, R.U., Z. Nikousefat, V. Tufarelli, S. Naz, M. Javdani and V.Laudadio. 2012. Garlic (Allium sativum) supplementation in poultry diets: Effect on production and physiology. World Poultry Sci. J. 68: 417-424.

Khan, S.H. 2014. The use of green tea (Camellia sinensis) as a phytogenic substance in poultry diets. Onderstepoort J. Vet. Res. 81(1): Art. #706, 8 pages. http://dx.doi. org/10.4102/ojvr.v81i2.706

Koscova, J., R. Nemcova, S. Gancarcikova, Z. Jonecova, L. Scirankova, A. Bomba and V. Buleca. 2006. Effect of two plant extracts and Lactobacillus fermentum on colonization of gastrointestinal tract by Salmonella enteric var. Dusseldorf in chicks. Biol. Brat. 61(6): 775 – 778.

Kumar, M. and J.S. Berwal. 1998. Sensitivity of food pathogens to garlic (Allium sativum). J. Appl. Microbiol. 84: 213-215.

Lambert, R.J.W., P.N. Skandamis, P.J. Coote and G.J.E. Nychas. 2001. A study of the minimum inhibitory concentration and mode of action of oregano essential oil, thymol and carvacrol. J. Appl. Microbiol. 91: 453- 462.

Lee, K.W., H. Everts, H.J. Kappert, M. Frehner, R. Losa and A.C. Beynen. 2003. Effects of dietary essential oil components on growth performance, digestive enzymes and lipid metabolism in female broiler chickens. Br. Poult. Sci. 44:450–457.

Lee, K.W., H. Ewerts, A.C. Beynen. 2004. Essentiel oils in broiler nutrition. Intern. J. Poult. Sci. 3: 738-752.

Lewis, M.R., S.P. Rose, A.M. Mackenzie and L.A. Tucker. 2003. Effects of dietary inclusion of plant extracts on the growth performance of male broiler chickens. Br. Poult. Sci. 44 (Suppl. 1): 43-44.

Lippens, M., G. Huyghebaert and E. Cerchiari. 2005. Effect of the use of coated plant extracts and organic acids as alternatives for antimicrobial growth promoters on the performance of broiler chickens. Arch. Geflugelkd. 69: 261-266.

Lopez-Bote, C.J. 2004. Bioflavonoid effects reach beyond productivity. Feed Mix. 12: 12-15.

Lovland, A. and M. Kaldhusdal. 2001. Severely impaired production performance in broiler flocks with high incidence of Clostridium perfringens-associated hepatitis. Avian Pathol. 30:73-81.

Mamoun, T., A. Mukhtar and M.H. Tabidi. 2014. Effect of fenugreek seed powder on the performance, carcass characteristics and some blood serum attributes. Adv. Res. Agri. Vet. Sci. 1: 6-11.

Mathis, G.F., Hofacre C. and N. Scicutella. 2007. Performance improvement with a feed added coated blend of essential oils, a coated blend of organic and inorganic acids with essential oils, or virginiamycin in broilers challenged with Clostridium perfringens. International Poultry Scientific Forum, Atlanta, Georgia.

Naidoo, V., L.J. MC Gaw, S.P.R. Bisschop, N. Duncan and J.N. Eloff. 2008. The value of plant extracts with antioxidant activity in attenuating coccidiosis in broiler chickens. Vet. Parasitol. 153: 214-219.

Nakatani, N. 1994. Antioxidants from spices and herbs. In: Food phytochemicals for cancer prevention II: Teas, spices and herbs. In: ACS Symposium Series 547, HO, C.T., T Osawa, M.T. Huang, R.T Rosen, Ed. American Chemical Society, Washington, DC., 264-264.

Nakatani, N. 2000. Phenolic antioxidants from herbs and spices. BioFactors. 13:141–146.

Nascimento, G.G.F., J. Locatelli, P.C. Freitas and G. L. Silva. 2000. Antibacterial activity of plant extracts and phytochemicals on antibiotic-resistant bacteria. Braz. J. Microbiol. 31: 247-256.

Navid, J., M. Mozaffar and K. Kazem. 2013. Effect of dietary medicinal herbs on performance, egg quality and immunity response of laying hens. Adv. Env. Biol. 7(13): 4382-4389.

Nichol, R. and T. Steiner. 2008. Efficacy of phytogenics in commercial Lohmann Brown layers. In: Feed Ingredient & Additives Asia Pacific Conference, March 5, Bangkok, Thailand. Nisha, A.R. 2008. Antibiotic residus: A global health hazard. Vet. World. 1 (12): 375-377.

Piao, X.L., X.S. Piao, S. W. Kim, J. H. Park, H. Y. Kim and S.Q. Cai. 2006. Identification and characterization of antioxidants from Sophora flavescens. Biol. Pharm. Bull. 29: 1911–1915.

Platel, K. and K. Srinivasan. 2004. Digestive stimulant action of spices: A myth or reality? Indian. J. Med. Res. 119:167–179.

Rahim, A., A. Mirza Aghazadeh and M. Daneshyar. 2011. Growth performance and some carcass characteristics in broiler chickens supplemented with Thymus extract (Thymus vulgaris) in drinking water. J. Am. Sci. 7(11), 400-405.

Rahimi, S., T. Zadeh, M.A. Karimi, R. Omidbaigi and H. Rokni 2011: Effect of the three herbal extracts on growth performance, immune system, blood factors and intestinal selected bacterial population in broiler chickens. J. Agric. Sci. Technol. 13: 527- 539.

Rhayour, K., T. Bouchikhi, A. Tantaoui Elaraki, K. Sendide and A. Remmal, 2003. The mechanism of bacteriacidal action of oregano and clove essential oils and of their phenolic major components on Escherichia coli and Bacillus subtilis. J. Essent. Oil Res. 15: 286-292.

Ruberto, G., M.T. Barrata, M. Sari and M. Kaabeche. 2002. Chemical composition and antioxydant activity of essential oils from Algerian Origanum Glandulosum Desf. Flavour Frag. J. 17: 251-254.

Sari, M. , D. M. Biondi, M. Kaâbeche , G. Mandalari, M. D’arrigo , G. Bisignano, A. Saija, C. Daquino and G. Ruberto. 2006. Chemical composition, antimicrobial and antioxidant activities of the essential oil of several populations of Algerian Origanum glandulosum Desf. Flavour Frag. J. 21: 890-898.

Schiavone, A., F. Righi, A. Quarantelli, R. BrunI, P. Serventi and A. Fusari. 2007. Use of Sibyllum marianum fruit extract in broiler chicken nutrition: Influence on performance and meat quality. J. Anim. Physiol. Anim. Nutr. 91: 256–267.

Shelef, L.A. 1983. Antimicrobial effects of spices. Journal of Food Safety. 6: 29-44.

Shing, R., K.M. Cheng and F.G. Silversides. 2009. Production performance and egg quality of four strains of laying hens kept in conventional cages and floor pens. Poult. Sci. 88: 256-852.

Smith-Palmer, A., J. Stewart and L. Fyfe. 1998. Antimicrobial properties of plant essential oils and essences against five important food-borne pathogens. Lett. App. Microbiol. 26: 118–122.

Soltan, M.A., R.S. Shewita and M.I. El-Katcha. 2008. Effects of dietary anise seeds supplementation on growth performance, immune response, carcass traits and some blood parameters of broiler chickens. Int. J. Poult. Sci. 7: 1078 – 1088.

Srinivasan, K. 2006. Fenugreek (Trigonella foenum-graecum): A review of health beneficial physiological effects. Food Rev.Int. 22: 203–224.

Srivastava, K.C., A. Bordia and S.K. Verma. 1995. Garlic (Allium sativum) for disease prevention. South African J. Sci. 91: 68-77.

Wallace, R.J. 2005. Antimicrobial properties of plant secondary metabolites. In: Proceedings of the Nutrition Society. 63: 621-629; DOI: 10.1079/PNS2004393

Waldenstedt, L. 1998. Coccidial and clostridial infections in broiler chickens: influence of diet composition. Acta Uni. Agric. Suec. Agrar. 88: 1-61.

Waldenstedt, L. 2003. Effect of vaccination against coccidiosis in combination with an antibacterial oregano (Origanum vulgare) compound in organic broiler production. Acta Agr. Scand. 53: 101-109.

Waldenstedt, L., K. Elwinger, P. Thebo and A. Uggla. 1999. Effect of betaine supplement on broiler performance during an experimental coccidial infection. Poult. Sci. 78: 182-189.

Wei, A. and T. Shibamoto. 2007. Antioxidant activities and volatile constituents of various essential oils. J. Agric. and Food Chem. 55: 1737–1742.

Windisch, W.M., K. Schedle, C. Plitzner and A. Kroismayr. 2008. Use of phytogenic products as feed additives for swine and poultry. J. Anim. Sci. 86 (E. Suppl.): 140– 148.

Young, J.F., J. Stagsted, S.K. Jensen, A.H. Karlsson and P. Heckel. 2003. Ascorbic acid alpha-tocopherol and oregano supplements reduce stress induced deterioration of chicken meat quality. Poult. Sci. 82: 1343- 1351.

Zaika, L. 1988. Spices and herbs: Their antimicrobial activity and its determination. J. Food Safety. 9: 97-118.

This paper was originally published at the Global Journal of Animal Scientific Research, . 2(3):234-243. 2014. Online ISSN: 2345-4385