Vol.5, No.8, 1210-1215 (2013) Health
Effect of onion (Allium cepa L.) as an antibiotic
growth promoter substitution on performance,
immune responses and serum biochemical
parameters in broiler chicks
Majid Goodarzi1*, Nasir Landy2, Shahram Nanekarani1
1Department of Animal Science, Borujerd Branch, Islamic Azad University, Lorestan, Iran;
*Corresponding Author: majidgoudarzi117@gmail.com
2Young Researchers Club of Islamic Azad University, Khorasgan Branch, Isfahan, Iran
Received 6 May 2013; revised 6 June 2013; accepted 1 July 2013
Copyright © 2013 Majid Goodarzi et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This experiment was conducted to evaluate the
effect of onion (Allium cepa L.) as an antibiotic
growth promoter substitute on growth perfor-
mance, immune responses and serum bio-
chemistry in broilers. A total of 192 one-d-old as
hatched broiler chicks (Ross 308) were weighed
and randomly allocated to four treatment groups,
each with 4 replicate pens of 12 chicks. The die-
tary treatments consisted of the basal diet (con-
trol), antibiotic (15 mg Virginiamycin/kg), and
control +10 or 30 g fresh onion bulb/kg diet.
Body weights of broilers were determined at d 1,
21 and 42, feed intake was determined at the
same periods, and feed conversion ratio was
calculated accordingly. At 14th and 21st days
blood samples were taken for measuring anti-
body titers against NDV and at 42nd day for bio-
chemical analysis. At d 42, two birds per repli-
cate were slaughtered for determination of lym-
phoid organ weight s. Dietary supplement ation of
30 g/kg onion increased final body weight of
broilers at 42nd d of age compared to the other
treatments (P < 0.05). Birds fed 30 g onion/kg in
the diet had the highest feed intake than other
treatments at different growth periods (P < 0.05).
Dietary treatments failed to induce any signifi-
cant effect on antibody titers against NDV, al-
though the weight of lymphoid organs was sig-
nificantly (P < 0.05) higher for birds fed diets
supplemented with 30 g/kg Onion. Broilers re-
ceiving 30 g/kg onion had a significantly higher
HDL and lower triglyceride concentrations com-
pared to control groups (P < 0.05). Feeding 30
g/kg onion resulted in a marked reduction in the
concentration of the glucose comp ared to control
groups (P < 0.05). The results suggested that die-
t ary inclusion of 30 g/kg onion can be applied as
alternatives to in-feed antibiotics for broiler diet s.
Keywords: Allium cepa; Onion; Broiler Chickens;
Immune Response; Serum Biochemical Parameters
Subtherapeutic feeding of antibiotics has historically
been a practice in some sectors of the commercial broiler
industry to promote growth performance and protect
flock health [1,2]. However, the use of dietary antibiotics
has resulted in controversial problems such as devel-
opment of antibiotic resistant bacteria and drug residue
in the final products [3] which can be harmful to con-
sumers. Thus, the use of antibiotics as a growth promoter
is no longer acceptable and it is forbidden in European
Union countries. As a result new alternatives are being
introduced to livestock producers, among which phyto-
genic and herbal products have been given considerable
attention as possible in-feed antibiotics substitutions. In
recent years, the use of phytogenic compounds has
gained momentum for their potential role as natural al-
ternatives to antibiotic growth promoters in animal nu-
triation [4,5].
The genus Allium includes about 550 species. A few
of these are important as food plants and as drugs in folk
medicine, notably onion (Allium cepa L.) and garlic (Al-
lium sativum L.). Onion is a bulbous plant widely culti-
vated in almost every country of the world with leading
Copyright © 2013 SciRes. OPEN A CCESS
M. Goodarzi et al. / Health 5 (2013) 1210-12 15 1211
production in China, India and United States [6]. Onion
bulbs possess numerous organic sulphur compounds in-
cluding Trans-S-(1-propenyl) cysteine sulfoxide, S-methyl-
cysteine sulfoxide, Spropylcycteine sulfoxides and cycl-
oallicin, flavinoid s, phenolic acids, stero ls including cho-
lesterol, stigma sterol, b-sitosterol, saponins, sugars and a
trace of volatile oil compounds mainly of sulphur com-
pounds [7]. Most of the plant parts contain compounds
with proven antibacterial, antiviral, antiparasitic, anti-
fungal properties and have antihypertensive, hypoglyce-
mic, antithrombotic, antihyperlipidemic, anti inflamma-
tory and antioxidan t activity [8].
Aji et al. [9] observed the beneficial influence of on-
ion bulbs on growth performance of broiler chickens.
Sebastian et al. [10] r eport ed that administr at ion of on ion
extract in rabbits significantly reduced serum, liver and
aorta triglycerides and serum and liver proteins. The aim
of this work was to evaluate the effects of the inclusion
of two levels of fresh onion bulbs on broiler responses
regarding growth, immune responses and serum bioche-
2.1. Animals and Dietary Treatments
One hundred ninety two, 1-d-old broi ler chickens (mean
initial weight: 3 5.5 ± 1 g) of mixed sex (Ross-308) were
weighed and randomly assigned to each of the 4 treat-
ment groups, each with 4 replicate pens of 12 chicks.
The dietary treatments included the basal diet (control),
control + 15 mg Virginiamycin/kg, or control + 10 or 30
g fresh onions (Allium cepa) bulb/kg diet. Table 1 lists
the basal diet formulated according to the nutrient re-
quirements of broilers provided by National Research
Council [11]. The birds were fed a starter diet from 0 to
21 d and grower diet from 22 to 42 d. All the dietary
treatments were added to the basal diets at the expense of
sand. Chicks were raised on floor pens (120 × 120 × 80
cm) for 6 wk and had free access to feed and water
throughout the entire experimental period. The lighting
program consisted of a period of 23 h light and 1 h of
darkness. The ambient temperature in experimental house
was maintained at 32˚C during the first week and gradu-
ally decreased by 3˚C in the second and third weeks, and
finally fixed at 22˚C thereafter.
2.2. Performance
Body weights of broilers were determined at d 1, 21,
and 42 of age. Feed intake and weight gain were re-
corded in different periods and feed conversion ratio
(FCR) was calculated. Mortality was recorded as it oc-
curred and was used to adj ust the to tal nu mber of birds to
determine the total feed intake per bird and FCR.
Table 1. The ingredient and calculated composition of basal
starter and grower diets.
Item Starter Grower
Ingredient, g/kg
Corn 505.1 524.6
Soybean meal 385 350
Soybean oil 35.8 59
Mono calcium phosphate 14.2 10
CaCO3 17.3 16.7
NaCl 3.1 2.1
NaHco3 2 1.6
Trace mineral premix1 2.5 2.5
Vitamin premix2 2.5 2.5
DL-Methionine 2.5 1
L-Lysine - -
Sand 30 30
Calculated composition
Metabolizable energy (kcal/kg) 2,900 3,100
Crude protein (g/kg) 215 200
Calcium (g/kg) 10 9
Available phosphorus (g/kg) 4.5 3.5
Methionine + cysteine (g/kg) 9 7.2
Lysine (g/kg) 11.8 10.9
1Provided the following per kg of diet: Mg, 56 mg; Fe, 20 mg; Cu, 10 mg;
Zn, 50 mg; Co, 125 mg; I, 0.8 mg. 2Provided the following per kg of diet:
vitamin A, 10,000 IU; vitamin D3, 2000 IU; vitamin E, 5 IU; vitamin K, 2
mg; riboflavin, 4.20 mg; vitamin B12, 0.01 mg; pantothenic acid, 5 mg;
nicotinic acid, 20 mg; folic acid, 0.5 mg; choline, 3 mg.
FCRFeed intakeweight gain
2.3. Immune Parameters
The commercially available oil-adjuvant injectable
emulsion against Newcastle Disease virus (NDV) and
Avian Influenza virus (AIV) were used (H9N2 subtype)
for vaccinating broiler chicks, and they were injected
subcutaneously with 0.2 mL per chick at 9 d of age. At
14 and 21 days of age two birds per replicate were ran-
domly chosen and blood samples were collected from the
brachial vein and centrifuged at 2000 ×g for 15 min to
obtain serum (SIGMA 4 - 15 Lab Centrifuge, Germany).
Antibody titers against NDV were measured using He-
magglutination Inhibition Test according to the method
of Thayer and Beard [12].
At 42 d of age, three birds per replicate were randomly
Copyright © 2013 SciRes. OPEN A CCESS
M. Goodarzi et al. / Health 5 (2013) 1210-12 15
Copyright © 2013 SciRes. OPEN A CCESS
chosen, based on the average weight of the group and
slaughtered through cutting carotid arteries and partial
slicing of the neck by a manual neck cutter; bursa and
spleen were collected, weighed and calculated as a per-
centage of live body wei g ht .
2.4. Serum Biochemistry
After 12 h of fasting, blood samples were collected in
non-heparinised tubes at day 42 of age from 8 birds in
each treatment by puncturing the brachial vein and the
blood was centrifuged at 2000 ×g for 15 min to obtain
serum (SIGMA 4 - 15 Lab Centrifuge, Germany). Indi-
vidual serum samples were analyzed for glucose, total
cholesterol, high-density lipoprotein (HDL) and low-
density lipoprotein (LDL) cholesterol and triglyceride
(Pars-Azm oo n C o., Tehran).
2.5. Statistical Analysis
The obtained data were subjected to analysis of vari-
ance procedures appropriate for a completely randomized
design using the General Linear Model procedures of
SAS Institute (2008). Means were compared using Dun-
can multiple test. Statements of statistical significance
are based on P < 0.05.
3.1. Performance Parameters
The impact of dietary treatments on growth perform-
ance indices from 1 to 42 day of age is presented in Ta-
ble 2. At 21 d of age BW of chicks did not differ (P >
0.05) between the dietary treatments, although BW of
broiler supplemented with 30 g onion/kg was higher than
other groups. At the end of the trial (d 42), birds supple-
mented with the 30 g onion/kg had a greater BW com-
pared with other groups (P < 0.05). The average daily
feed intake (from d 1 to 21) was increased (P < 0.05) for
bird supplemented with 30 g onion/ kg of diet. The av-
erage daily feed intake (ADFI) during grower and the
entire experimental period was higher for broilers sup-
plemented with 30 g onion/kg compared with control
birds and birds supplemented with antibiotic (P < 0.05).
Broilers receiving 10 or 30 g onion/ kg had a lower feed
conversion ratio (FCR) compared to broilers receiving
antibiotic during the starter period (P < 0.05), but FCR of
broilers in other periods was not affected. No differences
because of treatment effects were observed on mortality.
3.2. Immunity
The effects of treatments on immune related parame-
ters are shown in Tables 3 and 4. The additives used in
the current study failed to induce any significant impact
on antibody titers against NDV at 14 and 21 days of age
(P > 0.05). The weight of lymphoid organs was signed (P
< 0.05) higher for birds fed diets supplemented with 30
g/kg Onion.
3.3. Serum Biochemistry
Table 5 summarizes the impact of treatments on serum
constituents at day 42 of age. Treatments did not induce
any significant effect on the serum concentration of total
cholesterol and LDL-cholesterol. Broilers receiving 30
Table 2. Effect of experimental diets on performance indices of broilers at different ages.
Performance parameters Dietary treatments
Control Virginiamycin 10 g/kg Onion 30 g/kg Onion SEM1
Daily Feed Intake (g per bird/day)
0 - 21 d 31.4ab 31.4ab 29.4b 32.6a 0.33
21 - 42 d 122.5b 124.5b 128.9ab 133.5a 3.29
0 - 42 d 77.0b 78.0b 79.2ab 83.0a 1.96
Feed Conversation Ratio (g/g)
0 - 21 d 1.53ab 1.56a 1.51b 1.51b 0.005
21 - 42 d 1.87 1.89 1.92 1.89 0.014
0 - 42 d 1.79 1.81 1.83 1.81 1.010
Body Weight (g)
21d 465.8 463.8 447.1 477.5 16.79
42 d 1838.3b 1845.2b 1859.2b 1955.1a 14.84
Values in the same row not sharing a common superscript differ significantly (P < 0.05). 1Standard error of mean.
M. Goodarzi et al. / Health 5 (2013) 1210-12 15 1213
Table 3. Effect of experimental diet s on lymphoid organs at 42nd day.
Dietary treatments
Lymphoid organs Control Antibiotic 10 g/kg Onion 30 g/kg Onion SEM1
Bursaa 0.137d 0.165b 0.149cd 0.190a 0.010
Spleena 0.111b 0.139ab 0.138ab 0.148a 0.005
Values in the same row not sharing a common superscript differ significantly (P < 0.05). aPercentage of live body weight. 1Standard error of mean.
Table 4. Effect of experimental die ts on antibod y titers against Newcastle Disease Virus at 14th and 21st days.
Dietary treatments
Antibody titers (log) Control Antibiotic 10 g/kg Onion 30 g/kg Onion SEM1
14 days 0.619 0.650 0.643 0.650 0.016
21 days 0.739 0.775 0.775 0.775 0.019
1Standard error of mean.
Table 5. Effect of experimental diets on serum biochemical parameters of broilers at day 42.
Dietary treatments
Serum biochemistry Control Antibiotic 10 g/kg Onion 30 g/kg Onion SEM1
Triglyceridea 120.67a 111.25ab 104.25ab 95.75b 7.59
Total cholesterola 146.29 153.14 130.60 134.00 11.83
LDL-cholesterola 36.75 32.75 30.50 41.75 6.77
HDL-cholesterola 77.75b 94.25a 86.25ab 88.75a 2.89
Glucosea 93.75a 81.75ab 75.00ab 59.00b 7.37
Values in the same row not sharing a common superscript differ significantly (P < 0.05). 1Standard error of mean. a(mg/100 mL).
g/kg onion had a significantly higher HDL and lower
triglyceride concentrations compared to control groups
(P < 0.05). Feeding 30 g/kg onion resulted in a marked
reduction in the concentration of the glucose compared
to control groups (P < 0.05).
4.1. Performance
Dietary supplementation of 30 g/kg onion increased
body weight and feed intake of broilers at different
growth periods. Also, feeding 30 g/kg onion resulted in a
marked reduction in the concentration of the glucose.
Onion containing sulfur organic compounds including
S-Methylcysteine sulfoxide (SMCS) and S-allylcysteine
suiloxide (SACS) is related to decreasing of blood lipid,
liver protein and glucose. Hypoglycemia stimulates a
nerve center for intake whereas hyperglycemia stimu-
lates the center for satiety. Shurlock and Forbes [13] ob-
served reductions in feed intake after they infused glu-
cose into the hepatic portal vein of fasted chickens at
physiological rates, whereas no effect was observed
when glucose was infused into the jugular vein. Onion
stimulated growth by increasing the inflow of glucose
into tissues, thyroid like activity. The results of the pre-
sent experiment are consistent with Al-homidan [14].
Similar to our results Aji et al. [9] reported an enhance-
ment in BW, FCR and ADFI of broilers offered diets
containing fresh onion bulbs in comparison with broilers
fed basal diet. In this trial the positive impact of the on-
ion on the feed utilization was ob served at starter period,
but the improved FCR obtained in bro ilers supplemented
with 30 g onion/kg was not reflected at grower period
probably due to the facts that older birds’ nutrient re-
quirements decrease with age and also they have a better
developed digestive tracts and organs [4].
4.2. Immunity
With respect to a higher weight of lymphoid organs
recorded in chicks fed onion diets, it is concluded that
the active components of onion which have antibacterial,
antiviral, antifungal, anti inflammatory and antioxidant
activities [8] induce positive effects on these organs.
These results are in agreement with those obtained by
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M. Goodarzi et al. / Health 5 (2013) 1210-12 15
Ibrahiem et al. [15] who reported that bursa weights
were magnified by feeding onion to broiler muscovy
ducks. Onions have a mode of action which is similar to
antibiotics. Yamamoto and Glick [16] reported that the
synthesis of immunoglobulins was higher in chicken
with larger Bursa. Dafwang et al. [17] reported that the
effects of onion and garlic on immunoglobulins were si-
milar to antibiotics. But in the present trial that antibody
titers measured against NDV, neither positive nor nega-
tive effect was affected. Since antimicrobial agents start-
ed to be used as growth promoters, researchers [18,19]
working with broilers and swine respectively understood
that the presence of an important health challenge in the
field was essential to reveal the significant effects of
these products. This was while the current trial was con-
ducted in optimum cond itions and no external challeng es
or stresses were impelled to the broilers.
4.3. Serum Biochemistry
Broilers receiving 30 g/kg onion had a significantly
higher HDL and lower triglyceride concentrations com-
pared to control groups. Suresh and Srinivasan [20]
found that 3% onion powder reduced blood lipids, lipid
peroxides and cholesterol. Al-homidan [14] and Sebas-
tian et al. [10] also observed the reduced serum choles-
terol in their experiments by using of onion. In contrast
to the foreign experiments, Sklan et al. [21] did not
observe any effect of onion on hepatic cholesterol. The
effects of onion have been ascribed to its sulfur contain-
ing principles wh ich oxidize thiol compound s either pre-
sent free or combined with a protein and NADPH which
are necessary for lipid synthesis [10].
In conclusion, the results suggested that the dietary
inclusion of 30 g/kg onion can be applied as an alter-
native to in-feed antibio tics for broiler diets.
This study was supported by the Islamic Azad University, Borujerd
Branch, Lorestan, Iran.
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FCR = Feed conversion ratio;
NDV = Newcastle Disease virus;
AIV = Avian Influenza virus;
HDL = High-density lipoprotein;
LDL = Low-density lipoprotein;
BW = Body Weight;
ADFI = Average daily feed intake;
NADPH = Nicotinamide adenine dinucl eotide phosphate;
SEM = Standard error of mean.