dipl. oec. troph. rainer aschenbroichjul 01, 2015 · dipl. oec. troph. rainer aschenbroich rainer...
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secondary Plant compounds are more than essential oils
AbstractThe use of antibiotics for growth promoting
purposes in livestock is now banned for al-
most one decade in the European Union.
This has forced the development of alternati-
ve products replacing their beneficial effects
on health and productivity. Secondary plant
compounds have found their way into ani-
mal feed, since they possess promising pro-
perties known for centuries from their safe
and effective use in humans and animals. In
this review, we give a definition and classi-
fication of secondary plant compounds, de-
scribe their major mode of action and their
synergistic combination and we give examp-
les of their successful use in poultry.
IntroductionUnlike most animals, plants do not have
the ability to escape potential predators by
running away. To secure the survival of their
species, plants have evolved multiple me-
chanisms to defend themselves against po-
tential threats.
Most of these mechanisms are based on the
synthesis of a combination of compounds
with specific biological activities, which
have been recognized and used for appe-
tizing, digestive or therapeutic purposes for
many centuries in humans and animals.
In contrast to so called primary plant com-
pounds that are of importance for growth
and reproduction of a plant like carbohy-
drates, proteins and vitamins (Ehrlinger,
2007), secondary plant compounds are not
directly involved in the general energy and
nutrient metabolism but offer a benefit for
the plants in the natural selection process.
Some compounds, for example emit odors
to attract pollinating insects or as defensive
mechanism to protect against pathogens
or predatory herbivores thus preserving
the individual plant and the species respec-
tively (Westendarp, 2007).
The amount and the composition of secon-
dary plant compounds is determined by
many different factors like genetic configu-
ration and growth stage of the plant as well
as external influences like climate, weather
and soil conditions (Westendarp, 2007).
Between the different active substances
mutual interactions can be observed. The
special combinations determine the inten-
sity of the total impact and it is assumed
that substances with even very low con-
centrations can be significantly involved
in the mode of action (Westendarp, 2007).
This leads to the conclusion that isolated
or chemically synthesized single com-
pounds cannot have the same activity as
a mix of plant components acting synergi-
stically (Heinzl, 2010). Safrol for example as
single substance is very toxic for liver and
kidney and furthermore is assumed to be
carcinogenic. Consumed as an ingredient
of black pepper or nutmeg however, such
toxic effects are not observed. Secondary
plant compounds are of wide structural
variety. Most of the approximately 100,000
Secondary Plant Compounds are more than Essential Oils
Dipl. oec. troph. Rainer Aschenbroichrainer Aschenbroich studied human nutrition, food Law and food technolo-gy at the niederrhein university of Applied sciences and worked in key posi-tions in product development, quality assurance and quality management in the food industry before joining eW nutrition. he developed high technology blends of secondary plant compounds (natural oils, extracts and oleoresins) from herbs and spices for feed.
to contact the author: [email protected]
Vol. 49 (1), July 2015 | LOHMANN Information
13
known secondary plant compounds are
believed to be involved in the plant defen-
se and reproduction system. This diversity
of ingredients also offers a multimodal use
in animal nutrition.
It has to be considered that a specific
and effective application can only be im-
plemented if there is specific knowledge
about their composition and mode of ac-
tion (Westendarp, 2007).
Classification of secondary plant compounds:Secondary plant compounds can be ca-
tegorized in different ways. They are eit-
her distinguished based on their active
groups, chemical characteristics, commo-
nalities in biosynthesis or impact and pur-
pose of use (Westendarp, 2007).
Phenolic or polyphenolic substances
Phenolic or polyphenolic compounds
comprise a large family with over 4,000
diverse compounds widely distributed in
plants and their fruits.
They are produced by the plant for co-
loring, growth, reproduction and as de-
fense mechanisms. They are formed by
several hydroxyls connected to one or
more aromatic rings and possess a high
antioxidant capacity. They can be found
in fruits such as apples or cherries, in ve-
getables such as broccoli or onions, but
are also contained in red wine, chocolate
or green tea. Depending on their natural
function in the plant they can act in an
antimicrobial and antifungicidal or anti-
parasitic way in the gastrointestinal tract
of the animal (Giannenas, 2008).
Essential oils
The ISO standard 9235 (1997) defines
„essential oils“ as products, which are ex-
tracted from plant material (one single
species) by either distillation with steam
(in case of e.g. menthol), by mechanical
treatment at room temperature (e.g. cold
pressed as orange oil or lemon oil) or by
dry distillation.
They are mixtures of volatile, liquid, lipo-
philic compounds. They can be synthe-
sized in each part of the plant. Some plants
have the ability to build essential oils with
different compositions in different parts of
the plant and in practice most of them are
extracted by steam distillation.
Approximately 3,000 compounds have
been isolated and analysed from essential
oils. Whilst in some essential oil types only
a few components are present ore one
compound dominates, other essential oils
can be composed of up to 100 compo-
nents (Wald, 2003).
Due to that diversity it is difficult to deter-
mine the proportional efficacy of single
compounds in often complex mixtures
(Westendarp, 2007). But more and more
scientific studies demonstrate a wide an-
timicrobial activity of many essential oils.
Tanning agents
Tannins are special types of phenols. They
can be found in variable concentrations
in different parts of a plant. Since they in-
teract with proteins on mucous membra-
nes they are traditionally used in cases of
unspecific diarrheas, inflammation of the
oral cavity and the pharynx as well as to
cure slight skin lesions. Additionally tan-
ning agents are radical scavengers and act
as antioxidants. Furthermore they have
antimicrobial and antiparasitic effects.
Bitter substances cannot be allocated
to a chemically consistent group of ele-
ments. The commonalities in this group
are based on their bitter flavor. With oral
administration the production of saliva
and anapepsia is stimulated by the excita-
tion of the taste buds.
Pungent substances cannot be assigned
to chemical group either. Besides a stimu-
lation of saliva and anapepsia production
the oral administration causes an enhan-
cement of gut motility. Other effects are
enhancement of blood circulation, anti-
emetic, antimicrobial, germicidal and in-
secticidal (Westendarp, 2007).
Alkaloids can have a direct impact on the
nervous system, by agonistic or antagoni-
stic binding to neurotransmitter receptors.
Furthermore they can inhibit metabolic
enzymes or have interactions with intra-
cellular proteins. Alkaloids are mainly used
as analgesics, sedatives or against diarrhea.
Saponins can be found in about 75 % of
all plants and the individual forms vary
greatly. They can reduce cholesterol levels,
act fungicidally and some types show an
immune stimulating effect (Westendarp,
2007; Heinzl, 2010). Saponins are also used
for their reducing effects on ammonia
emissions in animal feeding, by inhibition
of urease activity (Veit et al., 2011).
Mode of actionSecondary plant compounds not only
exert one specific mode of action. For
most SPCs a broad range of efficacy has
been demonstrated. In poultry produc-
tion, some of the most important benefi-
cial attributes are mentioned below.
Stimulation of digestion
Stimulation of the sensor cells in the gas-
trointestinal tract. This results in higher
concentration of calcium ions followed
by an increased release of Serotonin. This
chemical messenger activates the muscles
14
of the digestive tract and the secretion of
digestive juices, which as a consequence
improves resorption of nutrients (Braun et
al., 2007).
Antimicrobial interaction on bacterial
cell integrity
a) Through interactions with transmemb-
rane proteins secondary plant compounds
can lead to changes in the transport capa-
city of sodium and potassium ions, which
diminishes the membrane potential ac-
ross the bacterial cell membrane.
b) Through lipophilic interactions, secon-
dary plant compounds can increase the
permeability of the cell membrane, dis-
turbing the balance of ion concentrations
and thus leading to an impairment of os-
motic pressure regulation.
c) Through uncoupling of the electron
transport chain, secondary plant com-
pounds can impair ATP generation and
thus energy production in the bacterial cell.
Increase of antioxidative activity
The antioxidant activity is related to the
capacity of polyphenols to act as metal-
chelators, scavengers for superoxide or
hydroxyl radicals, hydrogen donators and
inhibitors of the enzymatic systems res-
ponsible for initiating oxidation reactions
(Mielnik et al., 2008; Gobert et al., 2010;
Sayago-Ayerdi et al., 2009). Higher oxida-
tion is an index for lower meat quality. Nu-
merous studies have pointed out the posi-
tive effect of secondary plant compounds
on meat quality (Viuda-Martos et al., 2010;
Janz et al., 2007; Viuda-Martos et al., 2010;
Al-Mamary et al., 2002; Russo et al., 2000).
Secondary plant compounds especially
polyphenols and flavonoids generate a
positive effect on meat quality and thus
increase shelf-life by:
Reduction of lipid oxidation and micro-
bial growth in meat during storage
Delayed degradation of vitamin E in meat
Improved meat color conservation du-
ring storage
Moderation of aldehydes and alcohols
related to off-flavor in meat
Synergistic effectsBetween the different components syner-
gistic interactions, leading to an increase
in the efficacy of the single active com-
pounds have been observed in numerous
studies (Figure 1). Therefore the type of
combination determines the intensity
of the total effect. In such a composition
also substances present in very low con-
centrations can significantly contribute to
the overall mode of action (Heinzl, 2010).
Other important factors, influencing the
efficacy of single active compounds and
their combinations are determined by the
uptake rate, metabolisation and their avai-
lability at the preferred site of action in the
organism (Westendarp, 2007).
Trials, demonstrating the in vivo efficacy of special combinationsAnimal trials were conducted with ACTIVO,
a product line containing several seconda-
ry plant compounds acting in a synergistic
way. The trial parameters shown below are
representative for the three main modes
of action.
Figure 2: Feed conversion rate
Figure 1: Synergistic effects
secondary Plant compounds are more than essential oils
Vol. 49 (1), July 2015 | LOHMANN Information
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1. Activation of digestion:
The trial was conducted on a farm in the
Czech Republic with 189,300 (Control
group) and 62,300 (Trial group) Ross 308
chickens of mixed sex. The control group
was fed with standard feed + 150 g / ton of
a competitive product, the trial group recei-
ved standard feed + 100 g of ACTIVO / ton
(Figure 2). Outcome: Feed conversion rate of
animals fed ACTIVO significantly improves
when compared to a competitor product
2. Antimicrobial efficacy compared to
antibiotic growth promoters
In this trial commonly used feeding pro-
grams in Brazil applying AGP’s were com-
pared to a diet containing Activo based
on secondary plant compounds. For this
trial 1,120 Cobb male chicks were divided
into 7 different groups, which were fed as
mentioned in table 1. Experimental diets
were formulated with requirement le-
vels 10% lower than recommended. The
parameters “Feed intake”, “Growth”, “FCR”,
“Average final weight”, “Mortality” and “FEF
Index” were evaluated during 45 days (Fi-
gure 3). The trial was conducted in order
to show the positive effects of secondary
plant compounds in comparison to anti-
biotic growth promoters especially under
bad hygienic conditions. At days 11, 14,
17, and 24 birds were challenged with a
solution containing strained dirty (conta-
minated) bed litter and water in a propor-
tion of 15 g/L. Birds were allotted to boxes
containing reused wood shavings and fa-
cilities were not cleaned at the beginning
or during the experimental period as well.
Outcome: Activo shows similar results as
antimicrobial growth promoters in terms
of animal performance, thus indicating
good animal health. (Trial conducted by
Federal University of Viçosa, Viçosa, Minas
Gerais, Brazil)
3. Increase of antioxidative activities to
extend shelf life of meat
640 male animals were divided into 4
groups, each group with 8 replicates (20
animals / pen). The animals were fed as
shown in the following table.
After slaughter, breast samples were fro-
zen at -20°C for 30 days. Samples were
then thawed to examine lipid oxidation
level, by measuring the Malonedialdehy-
de content (Figure 4). Malonedialdehyde
(* MDA) is generated from reactive oxy-
gen species (ROS), and as such is assayed
in vivo as a bio-marker of oxidative stress
(Stancliffe et al., 2011). Outcome: ACTIVO
significantly decreases the level of lipid
oxidation during meat storage. Trial con-
ducted by Federal University of Viçosa, Vi-
çosa, Minas Gerais, Brazil.
SummaryBased on the current scientific knowledge,
numerous feeding trials and the successful
use in the market there is clear evidence
that well-matched combinations of secon-
dary plant compounds are superior to sin-
gle active substances in order to achieve
significant improvements in animal per-
formance.Figure 3: Replacment of AGPs
Figure 4: lipid oxidation
Day 1 to 21 Day 22 to 35 Day 36 to 45
t1 no Additive no Additive no Additive
t2 Activo® 100 g/t Activo® 100 g/t Activo® 100 g/t
t3 Activo® 100 g/t + enramycin 8 ppm
Activo® 100 g/t + enramycin 8 ppm
Activo® 100 g/t
t4 enramycin 8 ppm Activo® 150 g/t Activo® 150 g/t
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With increased knowledge about secon-
dary plant compounds and their modes
of action, we will be able to further create
well-suited combinations of selected sub-
stances. It will allow us, to fully exploit their
potential for individual species during dif-
ferent stages in their life cycle.
The fact that in more and more countries
the use of antibiotics in feed will be ban-
ned or phased out in the near future, will
further increase the demand for phytoge-
nic products as natural alternatives to anti-
biotic growth promotors.
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Co-authorLea Hesselmann
secondary Plant compounds are more than essential oils
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