Since the European Union’s (EU) ban on the use of Antibiotic growth promoters (AGPs) in animal feed in 2006, the need to find novel strategies to maintain and improve poultry gut health has become ever-important.

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2. S
ince the European Union’s (EU) ban on the use of
Antibiotic growth promoters (AGPs) in animal feed in
2006, the need to find novel strategies to maintain and
improve poultry gut health has become ever-important.
This is because over the years, use of AGPs has managed to
control a range of pathogens that can cause poultry intestinal disease.
These diseases, which include Coccidiosis and Necrotic Enteritis
(NE), can significantly affect the health and performance of birds and
result in severe economic losses in the industry.
Since the ban on AGPs in feed, these diseases have become
increasingly commonplace.
Components contained in essential oils such as Carvacrol and
Thymol found in Oregano oil offer an alternative and natural solution
in the war against poultry gut health diseases.
Cell invaders
Coccidiosis is caused by a protozoan parasite known as Eimeria that
invades the cells of the poultry intestine. Several species of coc-
cidia are known to affect poultry and they include Eimeria tenella,
E. acervulina, E. necatrix, E. maxima and E. brunette. Each species is
known to cause a separate disease, exhibiting a characteristic degree
of pathogenicity. Coccidia also have a genetically-fixed self-limiting
lifecycle, thus the severity of each coccidiosis is positively correlated
with the number of infected oocysts ingested.
Coccidia oocysts are practically ubiqui-
tous in the poultry environment and even
new houses where poultry have not been
kept previously will quickly become contami-
nated (Reid, 1989; Williams 2005).
Necrotic Enteritis (NE), on the other
hand, is associated with the gram posi-
tive, spore-forming anaerobic bacteria
Clostridium perfringens. This bacterium is
also common to the poultry environment
and forms part of the normal gut microbiota
in poultry and other species. There are five
major strains of C. perfringens labelled A to
E and classified on the basis of the toxins the
organism produces. Type A is the strain that
is most commonly found in the gastrointes-
tinal tract and associated with NE manifesta-
tion. Furthermore, NE is often associated
with prior infection of coccidiosis.
Both diseases can manifest themselves in two forms: acute clinical
characterised by sudden increase in flock mortality with no prior
warning symptoms or the sub-clinical form which is milder but usually
does not have any peak mortality.
With the subclinical form, production losses ensue due to
decreased digestion and absorption, reduced growth rate and
increased FCR resulting from intestinal damage. It is for this reason
the sub-clinical form is considered to result in the greatest economic
losses and therefore more important as it can persist in broiler flocks
undetected with birds and remain untreated for a long period of time
(Dahiya et al 2006).
History of disease treatment
First attempts at treating coccidiosis date back to an outbreak in
poultry 70 years ago, using sulphonamides. Through further experi-
mentation, poultry producers in the United States found in the late
1940s that the most economic method of treating the disease was
via continuous usage of sulphaquinoxalines in the feed. This not
only reduced mortality but also lessened morbidity of the disease
in poultry.
Since the 1950s, various types of anticoccidials have been
produced from different drugs and chemicals. Some of the older
chemicals such as amprolium and nicarbazine are still being used
today. Most are no longer in use or allowed in various countries,
due to proven toxicological findings or a lack of efficacy due to the
development of resistance by the coccidia.
In the 1970s a new class of antibiotics was discovered. These
were named the ionophores and eventually replaced the earlier
chemical compounds. Ionophores are unique, because they permit
a small amount of coccidian to survive and complete their life cycle
within the intestines of the bird, enabling the bird to develop a
certain level of immunity. This allows a greater degree of protection
against the parasite and is a very efficient method of control.
However, these more recent developments were still not able
to address the issue of resistance and soon enough, most species of
coccidian had developed resistance to all the ionophores available
in the industry.
Conversely treatment of NE has a much shorter history as even
as recently as 1997 it did not merit special attention in an interna-
tional poultry disease directory (van der Sluis, 1997). It was at the
beginning of the 21st Century it emerged as a worldwide problem.
A survey in 2001 indicated that 31 percent of broiler flocks in the
UK suffered from NE (Hermans and Morgan, 2003). The reason for
this is because NE in poultry has long been controlled incidentally by
some in-feed AGP’s including virginiamycin and bacitracin (Johansson
et al., 2004). Some in-feed ionophorous anticoccidial drugs also
possess activity against Gram positive bacteria such as Clostridium
perfringens (Watkins et al 1997). Withdrawals and reductions in the
use of in-feed AGPs have contributed to the growing incidence of
this disease.
The battle against coccidiosis and NE
An outbreak of coccidiosis and/or NE in a poultry flock has a very
negative economic impact for the poultry producer. There is an
immediate and considerable drop in production figures as well as
the recovery and re-establishment period after treatment being
slow. Some flocks never fully recover or regain their full production
potential.
NE carries further risk as the causative agent, Clostridium per-
fringens, poses a significant threat to public health too. Hence, it is a
well-recognised fact that treatment alone cannot prevent the eco-
Bot
Figure 1: The effect of oregano oil on sporozoite-infected enterocytes within the
lumen (Do you have a version of this without reference to Orego-stim or it is easy
to change to just oregano oil based product or something?)
The natural alternative to prevent Coccidiosis and Necrotic Enteritis
anical Warfareby Meriden Animal Health
20 | May - June 2014 GRAIN&FEED MILLING TECHNOLOGYF

3. nomic losses. It is well-established within the poultry sector that
the only choice is therefore prevention of the disease. However,
an effective and sustainable prevention and control programme
against the disease is not easy.
Coccidiosis is particularly difficult to combat because several
different species of Eimeria exist in the field. Poultry may become
infected with different species because the immunity that develops
after infection is specific only to one species. Eimeria has a very
complex life cycle that involves many developmental stages within
the host cells. Each Eimeria type is able to infect only one host
species and they each attack different segments of the intestine
in their host.
The disease carries losses for the producer in the form of mor-
talities, reduced market value of the affected birds and sometimes
culling or delayed slaughter time. Another predisposing factor is
the confined host-rearing conditions, which lead to an increase
in the numbers of oocysts, which are ingested by poultry via the
litter. These lead to destruction of the integrity of the intestinal
mucosae and interfere with nutrient absorption, ultimately causing
diarrhoea, which in turn causes high medication costs. Ultimately,
all these setbacks lead to huge losses for the producer.
Another factor is the increasing incidence of drug resistance to
field strains of coccidia. The conventional methods to control the
disease include using certain coccidiostats or coccidiocidal drugs.
Producers are adding a number of anticoccidial drugs to commer-
cial feed to control the recurring coccidial challenge. In the case of
salinomycin, it is known that at approximately day 28 of the broiler
production period, performance declines in birds receiving the
anticoccidial due to the presence of subclinical coccidiosis. Under
normal management conditions, this is a typical occurrence when
this ionophore is used.
To prevent widespread resistance to the narrow range of
anticoccidial drugs available in the field, nutritionists and veterinar-
ians have resorted to devising and implementing many different
forms of complex anticoccidial shuttle and rotational programmes
in an attempt to achieve optimal efficacy with minimal side effects.
However, the design, implementation and monitoring of such
programmes has become extremely complicated and fraught with
obstacles and risks. For example, poultry flocks cannot be treated
with nicarbazine during early autumn or spring because sudden
heat waves can result in high mortality, even in young birds.
Albeit still valuable to the industry, ionophores also have its
own share of dangers. Detectable residual levels of coccidiostats
have been found in commercial broiler meat and table eggs.
A relatively common problem that poses devastating conse-
quences is the accidental feeding of diets containing coccidiostats
to non-target animals. For instance, turkeys fed rations containing
salinomycin may encounter an increase in mortality, whereas
broiler breeders fed rations containing nicarbazine may be affected
by a drop in egg production and infertility.
Last but not least, producers need to consider the extra time
and money spent by the feed mill for flushing systems of coccidi-
ostat residues, the planning and mixing of various different batches
of medicated feed and attempts to avoid cross contamination of
drug-free withdrawal feed. Residual effects, if ever found in the
poultry meat or eggs, may pose a serious problem for producers
who wish to export their produce to countries where legislation
requires drug and residue-free chicken meat and eggs and where
demands for such healthy produce are on the rise.
Not only does subclinical infection NE impact on bird perfor-
mance but intestinal damage also allows the bacteria to reach the
bile duct and portal blood stream. When this occurs the liver can
be colonised by high numbers of C. perfringens resulting in cholan-
giohepatitis. Often liver lesions are found during meat inspection at
slaughter without any sign of clinical disease in the flock, resulting
in a large number of condemnations.
Prevention and management of NE is further compounded by
the multifactorial nature of the disease. A number of predisposing
factors have been implicated in the pathogenesis of the disease
including nutrition, stress and coccidiosis.
These factors contribute to creating an intestinal environment
that favours growth of C. perfringens. Diets with high levels of
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4. indigestible, water-soluble NSP such as wheat and barley are risk
factors as well as high dietary concentrations of animal protein.
Anything that results in high concentrations of protein in the
gastrointestinal tract is a predisposing factor as the protein acts
a substrate for the bacteria (Timbermont et al 2011). Any factor
that causes stress in the chicken, alters the intestinal environment
and could also induce NE. This could include changes in diets such
as moving from starter to grower diets and/or stocking density
(McDevitt et al 2006).
However, it is coccidosis that is the most important predispos-
ing factor. Coccidiosis outbreaks often precede outbreaks of NE
in the field. It has also been shown that Eimeria oocysts or an
overdose of commercial coccidiosis vaccines containing attenu-
ated Eimeria strains, act synergistically with C. perfringens (Park
et al 2008).
Eimeria parasites kill epithelial cells when they colonize the
small intestine. This allows plasma proteins to leak into the
gut lumen thereby creating a substrate for C. perfringens (Van
Immerseel et al 2004). In addition to this, C. perfringens is able
to utilize mucus as a substrate and intestinal mucogenesis is
increased in an immune response to coccidial infection (Collier
et al 2008).
Coccidial Vaccinations: A Boon or a Bane?
Vaccination is an obvious alternative system to control coccidiosis.
Currently, a number of coccidial vaccines have been developed
and used commercially. Most coccidial vaccines include a low
dose of the live parasite as a key ingredient to stimulate protec-
tive immunity. These have been used in millions of chickens.
However, the parasite can still cause disease in vaccinated chick-
ens if their immune systems are already compromised, damaged
or suppressed by other infectious agents.
In the field, once birds have been exposed to coccidia, they
develop immunity after approximately three cycles of oocyst
production. Although live or attenuated parasites have been
widely used as a commercial vaccine, antigenic variability between
the Eimeria species present in the vaccine and those in the field,
restricts the effectiveness of commercial vaccines.
There is also a price to be paid for protection against a poten-
tial threat. This could be in the form of the high cost of vaccines,
time spent administering the vaccines, losses due to vaccine reac-
tions in live vaccines and localized tissue damage in killed vaccines.
The disadvantages associated with the live vaccines are
problems with uniform vaccine application, excessive vaccine
reactions, unwanted spread of the vaccinal viruses, extreme
handling requirements needed to maintain viability of the vac-
cinal organisms and last but not least, the emergence of necrotic
enteritis. The relationship between coccidioses and NE is still
poorly understood and is therefore a major factor limiting use of
anticoccidial vaccine in broilers (Williams 2003).
Furthermore, the risk of vaccination failure cannot be totally
eliminated . A vaccination failure occurs when, following vaccine
administration, the chickens do not develop adequate protection
and are susceptible to a field disease outbreak. There are several
factors, including high levels of maternal antibodies, environmental
extremes, inadequate nutrition, parasitism and other concur-
rent diseases that can also contribute towards vaccine failure.
Improper handling or administration of the vaccine should also
be considered.
A new natural weapon: Botanical Warfare!
Essential oils from plants have been used by humans for centu-
ries for medical purposes so it is no surprise that with the ban
on AGP’s in the EU, there has been growing attention to their
potential as feed additives. Compared with synthetic antibiotics
or inorganic chemicals they are considered natural, less toxic and
residue-free (Hashemi et al 2008) and also offer a cost-effective
solution. Oregano oil in particular has been identified as a natural
alternative in the prevention of coccidosis and NE.
Oregano oil contains phenolic components called carvacrol
and thymol. These help to reduce mortality caused by gastroin-
testinal diseases by preventing the occurrences of gastrointestinal
22 | May - June 2014 GRAIN&FEED MILLING TECHNOLOGYF

5. pathogen invasion. Aside from offering a solution to coccidiosis and
NE, extensive research has demonstrated oregano oil can provide
additional performance benefits. Furthermore there is no evidence of
any bacterial or coccidian resistance from oregano oil. This is because
of the primitive and straightforward mode of action. No withdrawal
period is required either so, oregano oil can be used safely right up
until the slaughter period.
In humans and animals, the upper layer of enterocytes is constant-
ly shed and replenished every 4 to 7 days. Oregano oil speeds up
this natural renewal process creating an environment that is hostile
to the coccidial lifecycle. The sporozoite-infected cells are thus shed
before the next developmental stage thereby disrupting the life cycle
and preventing coccidiosis.
This rapid shedding of the intestinal cells also prevents thickening
of the intestines caused by E. coli and other pathogenic bacteria
that may be potential secondary invaders. The accelerated rate of
epithelial cell turnover results in lesser contamination of the emerging
enterocytes and improved absorption capacity for nutrients.
Further to this, a number of recent studies have reported that
essential oils can have a direct effect on the eimeria oocysts. Remmal
et al (2013) tested the in vitro efficacy of eight EO components at
killing oocysts and carvacrol, the main constituent in oregano oil,
was found to have the greatest efficacy of those tested. Thymol also
ranked highly compared to the other components tested.
In a trial conducted in the USA by Colardo Quality Research
Incorporated, an oregano oil-based product was fed to chicks that
had been challenged with coccidiosis oocysts in order to evaluate
the ability of the product to protect against a coccidiosis challenge, in
comparison to a commonly used ionophore coccidiostat, which was
salinomycin. The results indicate that the Oregano-based product
gave effective protection against the coccidiosis challenge. The level
of protection achieved by the oregano product group was similar to
the protection provided by salinomycin at 55gr/tonne.
In the same experiment, performance of chicks fed Orego-Stim
in the presence of a necrotic enteritis challenge was also evaluated.
Oregano oil was compared with Bacitracin Methylene Disalicylate
(BMD) in this part of the experiment. Results showed that the oreg-
ano product gave effective protection against the necrotic enteritis
challenge model. The level of protection achieved by the Oregano
product was similar to protection provided by BMD at 27.5gr/tonne.
Carvacrol and thymol have both been demonstrated to have
anti-microbial activity against C. perfringens as well as other patho-
gens including salmonella and e. coli. In vivo studies in broilers have
further demonstrated the antimicrobial efficacy of oregano oil against
C. perfringens and hence protection against NE (Jamroz et al 2003;
Mitsch et al 2004). The mechanism of antimicrobial control is poorly
understood but it is believed to be related to the potential of the
hydrophobic essential oils to intrude into the bacteria cell, disinte-
grate membrane structures and cause ion leakage.
Clearly this antimicrobial effect will have beneficial effects on
the gut microbiota and health in general, thereby improving perfor-
mance. The reduction in immune response has further benefits for
performance. However positive effects on nutrient digestibility have
also been reported. Halle et al 2004 have reported improved feed
efficiency with carvacrol and thymol. Essential oils stimulate digestive
secretions; bile, mucus and enzyme activity were also reportedly
enhanced (Platel and Srinivasan 2004). Carvacrol and thymol also
have significant antioxidant properties (Cuppet and Hall, 1998).
Taking all of this into account, botanical warfare through the use
of essential oils such as oregano oil, offers a viable alternative for
the natural prevention of coccidiosis and NE, as well as supporting
poultry gut health. However it is important to note that in the litera-
ture, some discrepancies exist in the efficacies of essential oils. This
is because they can vary in composition and quality according to the
processing they have been subjected to, therefore it is important to
use a product which contains high specification oregano oil, with the
right balance of carvacrol and thymol with proven efficacy.
References
Collier, c.T., Hofacre, C.L., Payne, A.M., Anderson, D.B., Kasier, P., Mackie, R.I.
and Gaskins, H.R. (2008). Coccidia-induced mucogenesis promotes the onset
of necrotic enteritis in chickens. Veterinary Immunology and Immunopathology
122, 104-115.
Cuppet, S.L. and Hall, C.A. (1998). Antioxidant activity of Labiatae. Advances in
Food Nutrition Reseach 42, 245-271.
Dahiya, J.P., Wilkie, D.C., Van Kessel, A.G. and Drew, M.D. (2006). Potential
strategies for controlling necrotic enteritis in broiler chickens in post-antibiotic
era. Animal Feed Science and Technology 129, 1-2, 60-88.
Hashemi, S.R., Zulkifli, I., Hair-Bejo, M., Farida, A. and Somchit, M.N. (2008). Acute
toxicity study and phytochemical screening of selected herbal aqueous extract in
broiler chickens. International Journal of Pharmacology 4, 352-360.
Hermans, P.G. and Morgan, K.L. (2003). The epidemiology of necrotic enteritis in
broiler chickens. Research in Veterinary Science 74, supplement A, 19.
Jamroz, D., Orda, J., Kamel, C., Wiliczkiewicz, A., Wertelecki, T and Skorupinska,
J. (2003). The influence of phytogenetic extracts on performance, nutrient
digestibility, carcass characteristics and gut microbial status in broiler chickers.
Journal of Animal Feed Science 12, 583-596.
Johansson, A., Greko, C., Engström, B.E. and Karlsson, M. (2004). Antimicrobial
susceptibility of Swedish, Norwegian and Danish isolates of Clostridium
perfringens from poultry and distribution of tetracycline resistant genes.
Veterinary Microbiology, 99, 251-257.
McDevitt, R.M., Brooker, J.D., Acamovic, T. and Sparks, N.H.C. (2006) Necrotic
enteritis: a continuing challenge for the poultry industry. World’s Poultry Science
Journal 62, 221-247.
Mitsch, P., Zitterl-Eglseer, K., Kohler, B., Gabler, C., Losa, R. and Zimpernik, I.
(2004). The effect of two different blends of essential oil components on the
proliferation of Clostridium perfringens in the intestines of broiler chickens.
Poultry Science 83, 669-675.
Park, S.S., Lillehoj, h.S., Allen, P.C., Park, D.W., FitzCoy, S., Baurista, D.A. and Lillehoj,
E.P. (2008). Immunopathology and cytokine responses in broiler chickens
coinfected with Eimeria maxima and Clostridium perfringens with the use of an
animal model of necrotic enteritis. Avian Diseases 52, 34-39.
Platel, K. and Srinivasan, K. (2004). Digestive stimulant action of spices: A myth
or reality? Indian Journal of Medical Research 119, 167-179.
Reid, W.M. (1989). Recommending sanitary practices for coccidiosis control. In P. Yvoré
(Ed.), Coccidia and Intestinal Coccidiomorphs (pp 371-376). Paris: INRA.
Williams, R.B. (2003). Coccidial and clostridial interactions in broilers vaccinated
against coccidiosis. World Poultry, Special Supplement Coccidiosis,4, 26-28.
Remmal, A., Achahbar, S., Bouddine, L., Chami, F. and Chami, N. (2013).
Oocysticidal effect of essential oil components against chicken eimeria oocysts.
International Journal of Veterinary Medicine Article ID 599816, 8 pages DOI:
10.5171/2013.599816
Timbermont, L., Haesebrouck, F., Ducatelle, R., Van Immerseel, F. (2011). Necrotic
enteritis in broilers: an updated review on the pathogenesis. Avian Pathology
40, 4, 341-347.
Watkins, k.L., Shryock, T.R., Dearth, R.N. and Saif, Y.M. (1997). In-vitro
antimicrobial susceptibility of Clostridium perfringens from commercial turkey
and broiler chicken origin. Veterinary Microbiology, 54, 195-200.
Williams, R.B. (2005). Intercurrent coccidiosis and necrotic enteritis of chickens:
rational, integrated disease management by maintenance of gut integrity. Avian
Pathology 34, 3, 159-180.
Van der Sluis, W. (1997). Poultry diseases around the world. World Poultry, 13,
7, 32-44.
Van Immerseel, F., De buck, J., Pasmans, F., Huyghebaert, G., Haesebrouck, F. and
Ducatelle, R. (2004). Clostridium perfringens in poultry: an emerging threat of
animal and public health. Avian Pathology33, 537-549.
Figure 2: Oregano oil based product weight gain (Bar) &
Feed conversion (Line) 11-19 days
May - June 2014 | 23GRAIN&FEED MILLING TECHNOLOGY F

6. 24 | May - June 2014 GRAIN&FEED MILLING TECHNOLOGY
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