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Review of the Application of Garlic, Allium sativum, in Aquaculture

Authors:

Abstract

The extensive use of antibiotics and various chemical compounds has resulted in drug residue and resistant pathogens in treated fish. Drug residue not only pollutes the environment, but also threatens human consumers. In contrast, garlic as a well‐known natural antibiotic that causes no environmental or physical side effects has shown to be effective for the treatment of many diseases in humans and animals owing to its antimicrobial, antioxidant, and antihypertensive properties. In aquacultural operations, garlic with dose optimization is strongly recommended. This review focuses on the application of garlic in various fish diseases treatments and the prospects of using garlic preparations in aquaculture.
JOURNAL OF THE
WORLD AQUACULTURE SOCIETY
Industrial aquaculture is growing rapidly
in many developed and developilrg countries
due to the depletion of fisheries and market
forces aimed at globalizing food sources (Gold-
burg et al. 200t; Goldburg and Naylor 2005).
This impressive industrial development has
been accompanied by certain practices that can
potentially damage human and animal health
(Goldburg and Naylor 2005; Naylor and Burke
2005), such as passing large amounts of drugs
into the environment (Haya et al. 2000; Boxall
et aL.2004). Antibiotics have been used exten-
sively in industrial aquacultural operations for
various reasons (Jayaprakas and Sambhu 1996).
Although they confer positive effects on fish
and shrimp (Sambhu 1996), antibiotics cannot
be recommended for use due to their resid-
ual and other side effects, which can lead to a
myriad of problems. In marine fish hatcheries,
the indiscriminate use of antibiotics for pro-
phylaxis has led to the development of resis-
tant microbial strains (Brown 1989). Moreover,
drug resistance in fish pathogens can be trans-
ferred to environmental and human pathogenic
bacteda. Thus, the accumulation of antibiotics
in fish can be harmful to the environment as
well as consumers. Accordingly, many coun-
tries refuse to import cultured products. These
Vol.43, No.4
August, 2012
problems have prompted scientists to search for
an alternative to antibiotics.
Garlic, Allium sativum L., has a reputation as
an "a1l-healing" herb. Garlic has been proven
effective as a hypolipidemic (Sumiyoshi 1997),
antimicrobial (Kumar and Berwal 1998), anti-
hypertensive (Suetsuna 1998), hepatoprotec-
tive, and insecticidal (Wang et al. 1998) agent
in various human and animal therapies. Gar-
lic extracts have also been shown to reduce
serum cholesterol levels (Bordia et al. 7975;
Augusti 1977) and increase blood coagula-
tion time (Bordia et al. 1975). In aquacultural
operations, garlic promotes growth, enhances
the immune system, stimulates appetite, and
sffengthens the conffol of pathogens, especially
bacteria and fungi. Many reports have doc-
umented that garlic can effectively eliminate
principal pathogenic bacteria in freshwater fish,
including Pseudomonas fluorescens, Myxococ-
cus pis cic ola, Vibrio anguillarum, Edw ardsiella
tarda, Aeromonas punctata f. intestinalis, and
Yersinia ruckeri. As a food additive in fish.
garlic has a food calling effect and improves
flesh quality. Garlic may also prevent heavy
metal-induced alterations in the lipid profile
(Gupta et al. 2008). These effects of garlic are
attributed to the presence of various organosul-
fur compounds, including allicin (Augusti et al.
1974). Garlic extracts and most commercial
Review of the Application of Garlic, Allium sativum,
in Aquaculture
JEoNc-Yeor LnEl lNn YnNc Gno
Department of Aquaculture and Aquatic Science, Kunsan National University, Kunsan, Korea
Abstract
The extensive use of antibiotics and various chemical compounds has resulted in drug residue
and resistant'pathogens in treated fish. Drug residue not only pollutes the environment, but also
threatens human consumers. In contrast, garlic as a well-known natural antibiotic that causes no
environmental or physical side effects has shown to be effective for the treatment of many diseases
in humans and animals owing to its antimicrobial, antioxidant, and antihypertensive properties, In
aquacultural operations, garlic with dose optimization is strongly recommended. This review focuses
on the application of garlic in various fish diseases treatments and the prospects of using garlic
preparations in aquaculture.
@ Copyright by the World Aquaculture Society 2012
'Corresponding author
447
448 LEE AND GAO
garlic food supplements including tablets and
capsules containing garlic powder, are based
on either the allicin content or the potential to
produce allicin (Lawson and Wang 2001). The
content of allicin and other sulfurous chemicals
in garlic varies widely and depends on sev-
eral factors. For medicinal applications, higher
levels of allicin are favorable (Huchette et al.
2005). However, the real content of effective
ingredients in a garlic product and whether they
can work well in an aquatic environment need
to be verified.
The application of garlic as a therapeutic
agent in humans and poultry has a long his-
tory. The utilization of garlic in aquaculture has
developed alongside the application and popu-
larization of Chinese herbs in aquaculture. Most
aquatic garlic research has involved fresh gar-
lic extracts, with experimental subjects either
fed a garlic-added feed or treated with a gar-
lic juice immersion. This review will focus on
the available literature on the use of garlic in
aquatic treatments, locating the gaps and con-
straints of recent research, and providing topics
for potentially instructive studies.
Effect of Garlic as a Feed Stimulator
and Growth Promoter
Herbs perform their initial activity in feeding
as a flavor and thereby influence eating patterns,
the secretion of digestive fluids, and total feed
intake. The stimulation of digestive secretions,
including saliva, digestive enzymes, bile, and
mucus, is considered to be an important action
of phytobiotics.
Allicin has an intense garlic flavor with a
strong stimulatory effect on olfaction in most
aquatic animals, including Pelodiscus sinensis,
Ctenopharyngodon idellus, Cyprinus carpio,
Carassius auratus. and Oreochromis nilotiEus.
Allicin can induce fish to ingest, increasing feed
intake. Harada (1990) reported that garlic had
a strong food calling effect on loach (Oriental
weatherfish) and Japanese amberjack, Seriola
quinque radiata Temminck et Schle gel.
Allicin can also inhibit and kill various
pathogenic bacteria, enhance immunocompe-
tence, improve gastrointestinal motility, and
modulate the secretion of various enzymes
to improve digestion and nutrient absorption.
Other research has indicated that allicin can
improve digestion by promoting the perfor-
mance of the intestinal flora, thereby enhancing
the utilization of energy and improving growth
(Khalil et al. 2001). Some reports showed that
garlic can inhibit deleterious bacteria while
intensifying beneficial bacteria, such as Lac-
tobacillus bifidus. Tang et al. (1997) claimed
that allicin could react with vitamin 81 (VB1)
to form allithiamine. which is more stable and
digestible than VB1. Meanwhile, allithiamine
can inhibit the decomposing effect of thiami-
nase, ensuring the supplication of VB1 and
improved growth in fish.
Many repofts have documented the effect of
allicin as a growth promoter. Fo et al. (1990)
mixed a I7o garlic residue premix with the
feed of grass carp, C. idellus, and common
carp, C. carpio, in a polyculture system. After
3 mo of breeding, the feed intake rates of the
grass carp and common cafp were improved,
and the feed coefficient decreased 23.5Vo. Zeng
et al. (1996) reported that when 50 mg/kg
synthesized allicin was added to tilapia feed,
the weight gain and survival rates increased by
more than 2-37o after 45 d. the feed conversion
ratio increased llVo, and biological appraisal
was 127o higher than in the control group.
Jia et al. (1999) found that the addition of 50
and 100 mg/kg allicin to soft-shelled turtle feed
increased the weight gain rate by 26.97 and
45.3557o (P < 0.01), the feed conversion ratio
by 15.18 and I7.377o, and the survival rate
by 2.44 and 2.967o, respectively, compared to
the control group. Similar results were obtained
in common carp when 100 mg/kg synthesized
allicin and iodized allicin were added to carp
feed (Jia et al. 1997,1999; Hu 1999).
Shalaby et al. (2006) reported that the final
weight and specific growth rate of O. niloticus
increased significantly with increasing levels
of A. sativuim. These results are in agreement
with those obtained by Khattab et al. (2004).
In addition, Aly et al. (2008) and Aly and
Mohamed (2010) examined the growth rates of
Nile tilapia after feeding with garlic (10 and
REVMW OF TIIE APPLICATION OF GARLIC, ALUUM SATNUM, IN AQUACUUTURE 449
20 glkgdiet fed), and found statistically non-
significant increases after 1 or 2 mo, but a
significant increase only after 8 mo, indicating
that high doses or a long period was needed
to enhance the growth rate. The most effec-
tive ingredient in garlic (allicin) is unstable, so
the efficacy of garlic may vary considerably by
species and preparation.
On the other hand, negative effects have also
been reported. Ndong and Fall (2007) rsported
that hybrid tilapia fed a garlic-supplemented
diet at 0.5 and lVo exhibited no improvement
in growth compared to those fed a control diet
after 2-4 wk. This may be due to the brief
experimental period, or the fact that the fish
used in the experiment were larger (25.5 +
1.0 S) than those used in the aforementioned
two experiments (7 * 1 and 6.5 + 1.0 g, respec-
tively), so the growth performance was not
obvious. A negative effect was also observed
in Manila clam, Ruditapes philippinarum (Yang
et al. 2010). The hatching rate of Manila clam
decreased with increasing concentrations of
garlic extract. The application of t6 mg[L ga:.-
lic extract resulted in delayed embryo develop-
ment, and 32 mg/L resulted in hatching failure
of the embryos. During the planktonic stage,
larval growth was depressed by garlic exffact;
larval survival and metamorphosis increased
and then decreased as the garlic extract concen-
tration increased. The 16 mglL garlic extract
appeared to be optimal for larval metamor-
phosis and survival. The growth and survival
of juveniles also increased and then decreased
as the garlic extract concentration incteased,
with 8 mgl[- being the optimum concentra-
tion. This suggests that the effects of garlic
are affected by dosage, fish species, and devel-
opment stage. A similar finding was reported
by Huang et al. (2001), who reported that rice
field eel, Monopterus albus, died within 3 d of
being fed 800 mg/kg composed allicin. Xiang
and Liu (2002) found that the growth rate of
Colossoma barchypomum incteased and then
decreased with increasing amounts of allicin.
These results indicate that extremely high
concentrations of garlic extract or allicin do not
improve fish growth; instead, they are harm-
ful to fish health. This mav be because too
much alkyl sulfide reaches the intestine, inter-
fering with normal metabolism and suppress-
ing mitosis, resulting in slow growth and even
death. Yang et al. (2010) observed the inges-
tion behavior of larval R. philippinarurn that
became passive after being fed garlic (gastroin-
testinal color became delicate), but recovered
soon after the water was changed. This suggests
that the inhibitory effect of high concenffations
of garlic extract on larval and juvenile fish is
caused by the suppression of larval ingestion.
Therefore, garlic as a feed additive is not
optimal for all fish species, and the opti-
mal feeding amount is species-specific. Further
study is needed to determine the optimum garlic
concentration for specific fish species.
Effect of Garlic on Flesh Quality
Despite many studies on the effects of garlic
in aquaculture, little is known about the effect
of garlic on flesh quality. Currently, there is no
perfect system for evaluating the flesh quality
of cultured fish. Nonetheless, the contents of
crude protein, crude lipids, amino acids, water
loss rate, and folding endurance of muscle may
reflect the flesh quality to some extent. Long-
term feeding may lower the lipid and choles-
terol content of fish. Moreover, allicin could
activate intestinal proteases, which convert feed
protein into fish protein, increasing the content
of palatable amino acids. Xiang and Liu (2002)
reported that the addition of 25-100 mglkg
garlic to the diet increased the crude protein
content and reduced the crude lipid content of
C. barchypomum.Luo et al. (2008) found that a
compound from Eucommia ulmoides and garlic
could improve the flesh quality of grass carp,
C. idellus. Aly et al. (2008) reported rhat rhe
post-harvest flesh quality and shelf-life of fish
fed a garlic-supplemented diet were improved.
Metwally (2009) found that the protein con-
tent in whole fish increased significantly in the
group fed a garlic-containing diet, whereas the
total lipid and ash contents decreased signif-
icantly in the same group. These results are
in agreement with those obtained by Xiang
and Liu (2002), Abdelhamid er al. (2002),
450 LEE AND GAO
Khattab et al. (2004), Shalaby et al. (2006), and
El-Dakar et al. (2007).
Most fish feed is lacking in amino acids that
generate an aroma and palatable taste, such as
histidine, leucine, aspartic acid, and valine. The
fragrant ingredients of fish are generally sulfur-
containing base groups. Biochemical analysis
has indicated that garlic contains various alkyl
sulfide compounds and the C3H6S (O)-base
group, which relates to flesh aroma. Therefore,
the addition of garlic to feed could make up for
the shortage and improve flesh quality.
Effect of Garlic as an Antimicrobial
Substance
Much research has been conducted on the
inhibitory effects of garlic on the princi-
pal pathogenic bacteria of freshwater fish,
including P. fluorescens, M. piscicola, E. tarda,
Aeromonas hydrophila, A. punctata f. intesti-
nalis, Streptococcus agalactiae, and Staphy-
lococcus aureus. Table 1 lists the inhibitory
effects of garlic on several common fish bac-
terial pathogens.
Garlic has antibacterial activity against
A. hydrophila in freshwater, as reported by
Diab (2002) and Diab et al. (2002). Nya
and Austin (2009) reported that the use of
garlic-supplemented diets for 14 d led to a
marked reduction in mortality after challenge
with A. hydrophila. Only 47o mortalities were
recorded in groups fed 0.5 and l7o garlic-mixed
feed compared to 88% mortality in the con-
trol group. Sahu et al. (2007) obtained similar
results for controlling A. hydrophila infection
in Labeo rohita fingerlings, and they noted that
the 0.1 and 0.57o added groups showed the
highest level of survival (857o) compared to
the control group (5770). Aly and Mohamed
(2010) also found that O. niloticus fed a
3Vo garlic-supplemented feed showed a signif-
icantly increased survival rate (85Vo) after a
challenge withA. hydrophila. Zhang (2003) sur-
veyed the inhibitory effects of garlic on two
isolates of A. hydrophila, AHl and AH2, invitro
and found that the minimum inhibitory con-
centrations (MICs) were 15.6 and 1.95 mg/mI-,
respectively. When examined with infected Si/-
urus soldatovi meridionalis Chen (L977) at
50 mg garliclkg diet, there was an obvious
inhibitory and controlling effect on AH2, but
neither isolate was eradicated. This indicates
that a higher concentration or longer time may
be needed to obtain a healing effect in practice.
Rahman ,et al. (2009) evaluated the effi-
cacies of antibiotics and medicinal plants
on three common bacterial fish pathogens:
A. hydrophila, P. fluorescens, and E. tarda,
They found that young Thai silver barh (Bar-
bonymus gonionotus) fed a diet supplemented
with 8 mg/ml garlic showed the best recov-
ery rate (907o) during the 10-d experimental
period. This is almost in agreement with Lee
and Musa (2008), who reported that the MIC
of 18 isolates of E tarda nnged from 7.81 to
31.25 mg/ml-, within which ETls had an MIC
value of 7.81 mg/ml.
The reported MIC was 625 mglmL for
S. aureus at an inoculum density of 106
CFU/mL (Lee and Musa 2008). However,
Deresse (2010) reported that dilute solutions
of garlic completely inhibited the growth
of S. aureus at concentrations greater than
7.50 mg/ml (15.00-60.00 mg/ml) with an
S. aureus inoculum density of 104 CFU/mL.
Using the same protocol, garlic had a bacterici-
dal effect at 30 mg/ml using a clinical isolate
of S. aureus. This is different from the bacte-
ricidal concentrations reported by Sivam et al.
(1997) (160 pg/ml) and Rees et al. (1993)
(0.6-1.3 mg/ml). These differences may be
due to variation among garlic species across
countries, processing differences, or the inocu-
lum density.
Rattanachaikunsopon and Phumkhachorn
(2009) found that an aqueous extract of
A. sativum had an MIC > 500 pg/ml in O.
niloticus infected with .S. agalactiae, in con-
trast to the results of Lee and Musa (2008).
Thus, the efficacy of garlic can vary widely due
to differences in processing conditions, species,
or biological conditions.
Luo's (2006) in vitro experiment deter-
mined the MIC values of a garlic extract
for P. fluorescens, M. piscicola, and A" punc-
tata f. intestinalis to be 3.125, 0.195, and
REVIEW OF THE APPLICATION OF GARLIC,,AI,UUM SATNUM,IN AQUACIJLTURE
Teu-e 1. The inhibition effects of garlic on several common fish bacterial pathogens.
451
Strain MIC (mg/ml)' Experimental subject References
Aeromonas
hydrophila
Pseudomonas
fiuorescens
Edwardsiella tarda
Streptococcus
agalactiae
Staphylococcus
aureus
Myxococcus piscicola
Aeromonas punctata
f. intestinalis
Mycobacterium
marinum
AH1:15.6
AH2:1.95
(Zhang)
3.125 (Luo)
7.81 *3 1 .25 (Lee)
62.5 (Lee)
62.5 (Lee)
0.195
0.098
2.0 (Delaha)
Labeo rohita, Oncorhynchus
mykiss, Oreochromis
ni lo t ic us, Silur us so lda! ovi
meridionalis Chen.
Barbonymus gonionotus
Barbonymus gonionotus
O re o chromi s nilotic us,
Barbonymus gonionotus
Invitro only
Invitro only
In vitro only
Dicentrarchus labrax
Zharg (2003); Sahu et al. (2007); Lee and
Musa (2008); Nya and Austin (2009);
Rahman et al. (2009); Aly and Mohamed
(20 I 0)
Luo et al. (2006); Rahman et al. (2009)
Lee and Musa (2008); Rahman et al. (2009)
Lee and Musa (2008); Rattanachaikunsopon
(2009)
Lee and Musa (2008); Deresse (2010)
Luo et al. (2006)
Luo et al. 12006)
Delaha and Garagusi (1985); Colorni et al.
( I ee8)
MIC : minimum inhibitory concentration.
aMIC parameters were obtained from in vitro experiments.
0.098 mg/ml, respectively. They also showed
a synergistic effect between garlic and
E. ulmoides against P. fl,uorescens at a concen-
tration of 0.098 mg/mL. However, the combi-
nation was not effective against M. piscicola
and A. punctata f. intestinalis compared to gar-
lic alone. The minimum bactericidal concentra-
tion of garlic for P. fluorescens and A. punctata
f. intestinalis was 25 and 6.25 mglmL, respec-
tively. Garlic had no bactericidal effect on
M. piscicola; however, the combination of gar-
lic and E. ulmoides could klll M. piscicola
at a concentration of 25 mg/ml. This sug-
gests that garlic can work synergistically with
other medicinal plants; however, more research
is needed before such treatment is put into
practice.
Woo et al. (2010) found that non-specific
immune defense factors in olive flounder. Par-
alichthys olivaceus, were strengthened signifi-
cantly after either the injection of a 5Vo garlic
extiact or immersion in 0.25 g/I- garTicjuice. In
a challenge infection experiment with Strepto-
coccus iniae and E. tarda, the relative percent
survival values were much higher in the SVo
garlic exffact pre-injected group and O.25 g/I-
garlic juice immersed group than in the other
groups tested, fospectively.
Delaha reported that 30 strains, represent-
ing I7 species of mycobacteria, were inhibited
by various concenffations of garlic extract, as
measured by their failure to grow. The con-
centrations ranged from 1.34 to 3.35 mg/ml,
within which the MIC for Mycobacterium mar-
inum was 2.0 mg/mL. However, no eradication
of M. marinum in surviving sea bass, Dicen-
trarchus labrax, was found after the injection
of garlic extract at a concentration of approxi-
mately 0.9 mglml- (Colorni er al. 1998).
It appears that the in vitro studies of
the inhibitory power of garlic extract against
mycobacteria can be interpolated. It may be sur-
mised that very high levels in serum would have
to be achieved (Delaha and Garagusi 1985).
These high levels could be toxic to the thiol
groups of the animal or human being treated.
Additional studies in animals are needed to
determine the safe blood levels and overall
toxicity.
Effect of Garlic as an Antiprotozoal Agent
The antiparasitic effect of garlic has been
known for a long time; for example, it
is effective in treating intestinal parasites.
Reuter et al. (1996) showed that an exffact
of garlic was effective against a host of pro-
tozoa, including Opalina ranarum, Opalina
dimidicita, Balantidium entozoon. Entamoeba
452 LEE AND GAO
histolytica, Trypanosoma, Leishmania, Lep-
tomonas, and Crithidia. Few reports describe
the use of garlic extracts for the treatment of
parasitic diseases in fish; Ichthyophthirius mul-
tifiliis and Neoparamoeba pemaquidensis arc
the only two fish parasites that have been
described.
Ichthyophthirius multifilils is one of the most
pathogenic parasites affecting freshwater fish.
The use of malachite green is considered to
be the most effective treatment for this disease.
but this application has been discouraged due to
its mutagenic and teratogenic properties. Buch-
mann et al. (2003) investigated the effects of
garlic extract on L multifiljis theronts and tomo-
cysts lz vitro and found that it killed theronts
within 15 h at a concentration of 62.5 mg/I-,
but had no effect on tomocysts within 24 h at
30 mg/l-, except at concentrations of 117 and
570 mg/I-; the lethal concentrations for mala-
chite green were 0.1 and 0.15 mg/L, respec-
tively. Bartolome (2007) also showed that garlic
exffact (10-fi0%o) could effectively control
or delay I. multifiliis infection in fish. There
were substantial reductions in the number of
infested black mollies, and parasite-induced
fish mortality was reduced significantly. These
two experiments indicate that garlic can inhibit
I. multifiliis, but it cannot eradicate it as effec-
tively as malachite green. It can be concluded
that garlic may be used to reduce infections at
fish farms with minimal environmental effects,
but it cannot act as a pesticide.
Neoparamoeba pemaquidensis is the etio-
logical agent of amoebic gill disease (AGD)
and causes significant losses in marine-cultured
salmonids and turbot Scophthalmus maximus.
Peyghan et al. (2008) showed that a garlic
extract appeared to be completely effective
at killing a cultured strain (NP251002) of
N. pemaquidensis invitro at a dilution of 1:100
within 24 h.In addition, it was efficacious at
killing wild-type amoebae isolated from the dis-
eased fish, slowing the clinical signs of AGD.
However, it is necessary to study the toxicity
and pathological effect of garlic on Atlantic
salmon before using garlic to treat AGD in
farmed Atlantic salmon.
Principle Behind Garlic as an Antimicrobial
Agent
The extensive use of antibiotics has resulted
in serious health and environmental problems.
Consequently, we are in need of safe and
effective alternatives. In this context, immunos-
timulants have attracted significant attention.
Garlic is one of the most effective natural
immunostimulants with a reputation as a natu-
ral antibiotic. Garlic, A. sativum, has long been
used as a therapeutic measure for humans and
livestock. Various garlic preparations exhibit-
ing a wide spectrum of activity, including
antibacterial activity against gram-negative and
-positive bacteria (Cavallito and Balley 1944;
Adetumbi et al. 1986; Ankri and Mirelman
1999), antiviral activity (Weber et al. 1992),
antifungal activity (Yoshida et al. 1987 Gupta
and Porter 2001), and antiparasitic effects (Lun
et al. 1994; Ankri et al. 1997), have been
reported. Garlic also has beneficial effects on
the cardiovascular and immune systems (Hanis
et al. 2001), and its purported anti-cancer prop-
erties have attracted recent attention. Given
its use in human medicine and agriculture as
a proven prophylactic and therapeutic agent,
interest in garlic as an immunostimulant for
use in aquaculture has increased (Amagase
et al. 2001).
For many years, the use of garlic as an
antimicrobial agent has been accepted, and sev-
eral mechanisms of action have been proposed.
Generally, garlic takes effect by facilitating
the function of phagocytic cells and increas-
ing their bactericidal activities; however, it can
also stimulate natural killer cells, complement,
lysozyme, and the antibody responses of flsh.
The activation of these immunological func-
tions is associated with increased protection
against infectious disease. Garlic accelerates
phagocytosis by macrophages (Lau et al. 1991).
Martins et al. (200D verified that the addition
of A. sativum to fish diets increased the erythro-
cyte number, hemoglobin content, hematocrit,
leukocyte number, and thrombocyte number.
Aly (2008) suggested that garlic improved the
immune response of O. niloticus via a rapid
increase in monocytes, and that over a longer
REVIEW OF THE APPLICATION OF GARLIC, ALUUM SATNUM, IN AQUACULTURE 453
time frame it enhanced phagocytic activity,
which affords increased protection against an
immediate challenge with A. hydrophila, ilhts-
trating the anti-infection properties of garlic.
These findings are in agreement with those
obtained by Kyo et al. (1998), Iranloye (2002),
Ndong and Fall (2007), and Nya and Austin
(2009). Garlic supplementation induced signifi-
cant changes in serum total protein and globulin
in rainbow trout following 14 d administra-
tion (Nya and Austin 2009). The increases in
the serum total protein, albumin, and globulin
contents are considered to reflect strong innate
immunity (Wiegertjes et al. 1996; Jha et al.
2007). These data are in agreement with the
flndings of Siwicki (1989), who also obtained
an increase in total protein content after feeding
B-glucan and chitosan to fish. Globulin frac-
tions are certainly important for maintaining a
healthy immune system (Jha et al. 2007). The
gamma globulin fractions are the source of all
proteins necessary for immune functions in the
blood, whereas albumin is essential for main-
taining the osmotic pressure needed for proper
distribution of body fluids and acts as plasma
carrier and non-specific ligand with many bind-
ing domains (Jha et al.20O7).
Cavallito and Bailey (1944) found that the
antibacterial properties of crushed garlic could
be attributed mainly to allicin. Allicin, the
immunologically active component of garlic,
has been found to affect oxidative stress and
immune responses in several experimental sys-
tems. The inhibition of certain SH-containing
enzymes in microorganisms by the rapid reac-
tion of thiosulfinates with thiol groups was
assumed to be the main mechanism involved
in the antibiotic effect of garlic (Cavallito
and Bailey 1944).In amoebic parasites, allicin
was found to strongly inhibit cysteine pro-
teinases, alcohol dehydrogenases, and thiore-
doxin reductases (Ankri and Mirelman 1999),
which are critical for maintaining the coffect
redox state within the parasite. Allicin can also
completely inhibit RNA synthesis and partially
inhibit DNA and protein synthesis (Feldberg
et al. 1988); in fact, its antibacterial effect on
S. aureus may be due to the inhibition of RNA
synthesis (Deresse 2010). Inhibition of these
enzymes was obseryed at rather low concen-
trations (<10 pg/ml). In addition to the allyl
group, it has been reported that the disulfide
group in ajoene (Naganawa et al. 1996) and
sulfide bonds in the diallyl sulfide breakdown
products of allicin are necessary for garlic's
antimicrobial activity (Tsao et al. 2001). It has
been suggested that microbial cells are apt to
be affected because they do not have intracel-
lular thiol content adequate to counterbalance
the thiol oxidation by allicin and allicin-derived
products. Ajoene has been shown to inhibit
phosphatidyl choline synthesis in trypanosomes
(Urbina et al. 1993). Ajoene was also recently
shown to inhibit phosphatidylcholine biosyn-
thesis in the human pathogenic fungus Para-
coccidioides brasiliensls (San-Blas et al. 1997).
The inhibition capacities shown for ajoene
clearly suggest that additional microbe-specific
enzymes may also be targets for allicin.
However, other studies claim that the pro-
tective effect of garlic is associated with its
antioxidant properties (Pedraza-Chaverri et al.
2000; Rahman 2003). Many defense mech-
anisms activated by garlic counteract infec-
tion, including the production of superoxide
anions against A. hydrophila infection (Sahu
et al. 2007). An aqueous exffact of raw gar-
lic and dried powder was shown to scav-
enge hydroxyl radicals (Yang et al. 1993; Kim
et al. 2001) and superoxide anions (Kim et al:
2001). Metwally (2009) verified that the activity
of antioxidant enzymes, including glutathione
peroxidase, superoxide dismutase (SOD), and
catalase (CAT), in O. niloticzs increased sig-
nificantly compared to the control group after
feeding with garlic preparations. The same
result was reported by Li et al. (2008), wherein
the activities of CAT and SOD increased sig-
nificantly and malonaldehyde diethyt acetal
decreased in the allicin-supplemented group.
Schulz et al. (2004) reported that, garlic has
antioxidant properties, which could have inhibit
lipoxygenase enzymes, increase the antioxi-
dant capacity in hamsrers (Yaoling et al. 1998).
Lipid peroxidation of rats was conffolled with
the antioxidant S-allyl cysteine sulfoxide iso-
lated from garlic (Augusti and Sheela 1996).
Lipid peroxides, uric acid, blood glucose,
454 LEE AND GAO
total lipid, triglycerides, and cholesterol were
decreased significantly after treatment with gar-
lic oil, also in liver and kidney lipid peroxides
decreased significantly (Mamdouh and Abdel-
Raheim 2003). Glucose concentration in blood
serum reduced significantly in fish fed on diets
containing different sources of A. sativum (Met-
wally 2009). This condition was attributed to
improving of the antioxidant system in cell of
pancreas to produce insulin. Same results were
found in mice feeding with garlic where sig-
nificant decrease of serum glucose levels was
observed (Kumar and Reddy 1999; Thomson
and Ali 2003). Lower levels of plasma glucose
in fish have also been reported in the assessment
of biochemical effects of A. sativura (Sheela
and Augusti 1992). Reduction of total lipid in
blood serum of O. niloticus fed on diets con-
taining garlic in different forms is in agreement
with the study of Adler and Holub (1997) who
verified that serum total lipid and total choles-
terol decreased significantly in men treated with
garlic and fish oil alone or combined. Also,
Hussein et al. (2001) found that the serum total
lipid decreased significantly in albino rats after
administration of garlic. The sulfur-containing
compound of garlic may be increased the oxi-
dation of plasma and cell lipids by improving
fish health.
The involvement of mannose-binding lectin
is assumed to be another mode for improv-
ing immune responses (Nya and Austin 2009).
Lectin is regarded as the most abundant pro-
tein in garlic (Fenwich and Hanley 1985),
and it is said to bind bacterial cells, trigger-
ing the complement cascade (Janeway 1993)
and, subsequently, phagocytosis (Magnadottir
2006). Conversely, it is recognized that man-
nose constitutes an important surface compo-
nent of cells, including A. hydrophila (Merino
et al. 1996). Here, the mannose-specific lectin
is used as a means of attachment of the bac-
terial cells to the gut epithelium of the host,
thus serving as adhesin mediating the binding
of bacterial cells with phagocytic cells (Wright
et al. 1989).
There are also data suggesting that gefina-
nium, a therapeutic factor present in garlic, may
enhance natural kill cell and macrophage activ-
ity in experimental animals (Aso et al. 1985).
Outlook
In an aquarium trial, an experimental infec-
tion was resolved much faster through the use
of antibiotics (seven days) compared to medic-
inal plants (Rahman et al. 2009). Garlic has
an apparent inability to evoke resistance in
most bacteria because its mode of action is
completely different from that of other antibi-
otic substances (Gupta and Viswanathan 1955).
Sivam et al. (1997) noted that garlic has a broad
spectrum of activity, and it is known to act syn-
ergistically with antibiotics. A synergistic effect
of allicin against Mycobacterium tuberculosis
was found with antibiotics such as streptomycin
or chloramphenicol (Gupta and Viswanathan
1955). In combination with a fish vaccine, gar-
lic shows great potential as a means for increas-
ing the protective capabilities of fish while
reducing the vaccine dose (i.e., the immunos-
timulant will boost the potency of the vaccine,
thereby reducing the dose required to achieve
the same effect) (Jeney and Anderson 1993).
Additional clinical studies are needed to assess
the effectiveness of using an antibiotic/garlic
combination for bacteria that are difficult to
eradicate.
The application of garlic may be an effec-
tive part of proper fish health management.
Garlic is easily obtained, inexpensive, and acts
against a broad spectrum of pathogens. More-
over, garlic extracts can be given orally, which
is the most convenient method of immunos-
timulation, though immersion and injection
are usable alternatives. To date, most studies
have been confined to laboratory conditions.
The application of garlic preparations, com-
pounds of garlic, and other medicinal plants
under practical-farming conditions has been
documented in China. However, the efficacy
depends on the dose and mode of administra-
tion, and there is potential for overdosing and
unskilled use may have a negative impact; thus,
dose optimization is strongly recommended.
Furthermore various companies do sell it as an
aqueous solution, but the purity of such allicin
product is questionable since allicin is unstable,
the degree of instability depending on a range
of parameters including solvent, pH, concentra-
tion, and the presence of additives. Similarly,
commercial garlic supplements can lose their
potoncy as a result of alliinase inactivity. Thus,
despite allicin's potent antimicrobial activity,
its benefits remain predominantly at laboratory
level with little available quantitative data con-
cerning its ability to fight aquatic disease in
practice. We conclude that garlic can be used
in fish culture as an alternative to antibiotics
or chemotherapeutic agents; however, further
research is needed under practical conditions.
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... Owing to the use of harmful chemicals in fish farming, which threatened human health, several studies are attempting the introduction of vegetable supplements in fish feeds. Garlic, which has been widely used in traditional medicine since ancient times, is one such example of a vegetable plant supplement (1)(2)(3). ...
... Many reports have documented that garlic can effectively eliminate principal pathogenic bacteria in freshwater fish, including Pseudomonas fluorescens, Myxococcus piscicola, Vibrio anguillarum, Edwardsiella tarda, Aeromonas punctata f. intestinalis and Yersinia ruckeri (1). Garlic, used as a feed additive in fish breeding, is also used to raise meat quality. ...
... The most important criterion in fish feed development is the achievement of rapid growth at low feed cost. However, it is necessary to determine the likely influence on fish nutrient and fatty acid profiles caused by differences among feeds administered to fish (1,2). ...
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In this study, rainbow trout were fed for a total of 90 days with different feed mixes containing 0.00%, 1.00%, 1.50% and 2.00% garlic (Allium sativum). The effect of garlic on the growth performance, body composition and fatty acid profile of rainbow trout was researched. The starting weight of fish in the experimental group was approximately 64.12±0.29 gr, which increased to 234.12±3.54gr, 246.31±4.41gr, 258.74±4.42gr, and 268.79±4.79gr, while the difference in growth between the groups was observed to be statistically significant (p<0.05). At the end of the feeding period, the specific growth rate (SGR), the economic conversion ratio (ECR), the feed conversion ratio (FCR), the economic profit index (EPI) and the protein efficiency ratio (PER) were checked. In this study, the nutritional composition and fatty acid profiles of fish after 90 days of feeding were examined. As a result of this study, the supplementation of garlic to the diet given to rainbow trout caused an increase in their protein ratio and a decrease in their moisture content and fat ratio. Additionally, it led to a decrease in fatty acid and monounsaturated fatty acid levels and an increase in polyunsaturated fatty acids.
... Garlic contains several antioxidant (flavonoids, sulfur containing substrates: 4,5 dithia 1, 7 octadiene and allyl cysteine), hepatoprotective and antimicrobial compounds (Sharma et al., 2010). Literature evidenced that garlic possesses natural antibiotic, antimicrobial and antihypertensive elements that causes no side effects of environmental or physical and it is used effectively for the treatments of many diseases both in human and animals (Lee and Gao, 2012;Yang et al., 2020). Moreover, garlic contains antiparasitic compound that controls egg development, hatching success etc. (Militz et al., 2014). ...
... This could be due to the synchronized effect of garlic and Lactobacillus casei supplementation results in increased cellular competence against oxidative stress with subsequent decrease in lipid peroxidation and a higher number of healthy cells in enhancing GPx function with synbiotic fed fish. A number of studies have reported that garlic contains antioxidants which can inhibit the formation of free radicals, reinforce the uptake mechanism of endogenous radicals, and increase cellular antioxidant enzymes such as such as CAT and GPx (Lee and Gao, 2012;Naji et al., 2017;Shang et al., 2019;Szychowski et al., 2018;Valenzuela-Gutiérrez et al., 2021). ...
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The positive effect of dietary synbiotic supplementation on fish exposed to bacterial infection is poorly researched. The present study addressed the knowledge gap of dietary supplementation of Lactobacillus casei and garlic, Allium sativum, termed as synbiotic on the growth performance, lipid utilization, antioxidant activities, skin mucosal status, cytokine gene expression and intestinal epithelial responses following Vibrio harveyi infection in juvenile barramundi, Lates calcarifer. Juvenile barramundi with an initial weight of 9.16 ± 0.08 g were randomly allocated into 8 tanks of 300 L capacity each at a density of 20 fish per tank. The quadruplicate groups were fed either a non-supplemented control diet or the same control diet supplemented with 1% of garlic powder and 1% of L. casei (10⁹ CFU/mL) for 56 days. Results indicated that although the synbiotic supplemented diet did not produce any significant improvement in growth rate and feed utilization, lipid utilization and glutathione peroxidase activity were improved (P < 0.05). Synbiotic diet also reduced the intraperitoneal adipocyte cells size and increased the number of skin mucin cells. TEM micrographs showed an enhanced microvilli length with a normal intestinal morphological pattern in synbiotic fed fish compared to a leaky intestinal tight junction in the control when fish are subjected to V. harveyi infection. In addition, a significant improvement of the expression of immune responsive genes were found in synbiotic fed fish when compared to control. Overall, the results indicate that dietary synbiotic supplementation has the potential to improve antioxidant response and health welfare of barramundi.
... Phytogenics modulate gut microbiota, increase productive parameters, appetite stimulation and antipathogenic properties in both terrestrial and aquatic species, resulting in promising functional feed additives [10,52]. Extracts from Allium plants, mainly from garlic and onion, have been used as supplement for fish diets in different studies, showing beneficial effects on immune system, growth performance, and health status [53,54]. The effects of these Allium extracts are related to secondary metabolites and organosulfur compounds such as allicin, PTS or PTSO [23,24]. ...
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This study analyzes the potential use of an Allium-derived compound, propyl propane thiosulfonate (PTSO), as a functional feed additive in aquaculture. Gilthead seabream (Sparus aurata) juveniles had their diet supplemented with this Allium-derived compound (150 mg/kg of PTSO) and were compared with control fish. The effects of this organosulfur compound were tested by measuring the body weight and analyzing the gut microbiota after 12 weeks. The relative abundance of potentially pathogenic Vibrio and Pseudomonas in the foregut and hindgut of supplemented fish significantly decreased, while potentially beneficial Lactobacillus increased compared to in the control fish. Shannon’s alpha diversity index significantly increased in both gut regions of fish fed with a PTSO-supplemented diet. Regarding beta diversity, significant differences between treatments only appeared in the hindgut when minority ASVs were taken into account. No differences occurred in body weight during the experiment. These results indicate that supplementing the diet with Allium-derived PTSO produced beneficial changes in the intestinal microbiota while maintaining the productive parameters of gilthead seabream juveniles.
... Dietary supplementation of garlic is reported to improve feed conversion and protein efficiency (Agbebi et al., 2013;Nya and Austin, 2009) that significantly contribute to the growth of fish. Garlic specifically its active ingredient allicin modulates the total bacterial counts, and status of beneficial bacteria in the fish gut, kill various pathogenic bacteria, enhance immunocompetence, improve gastrointestinal motility, and modulate the secretion of various enzymes to improve digestion, nutrient absorption, and enhance the energy utilization, resulting in improved growth in fish (Foysal et al., 2019;Büyükdeveci et al., 2018;Lee and Gao, 2012). These reports support our findings. ...
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Motile Aeromonas septicaemia (MAS) caused by Aeromonas spp. is one of the major fish diseases that causes substantial losses in the aquaculture industry. The present study was conducted to screen the in vitro inhibitory effects of garlic extracts on Aeromonas veronii isolated from MAS, evaluate the effects of dietary inclusion of garlic extracts on growth and prevention of MAS in Labeo rohita. In vitro antibacterial activities of garlic aqueous and organic solvent extracts (ethyl acetate, methanol, ethanol, and acetone) were screened by disc diffusion assay. The minimum inhibitory concentrations (MICs) of ethyl acetate and methanol extracts were determined by using a quantitative bioassay method. Four groups of fish were fed garlic ethyl acetate extract at the rate of 0 (T1, control), 6.25 (T2), 12.50 (T3), and 25.00 (T4) mg/kg feed with three replications for 90 days. The fish fed with different concentrations of garlic extracts were artificially challenged with the high virulent A. veronii strain B55. In this study, ethyl acetate extract of garlic inhibited all the A. veronii strains (A22, B7, B9, B19, B27, B36, B55, F143, K743, and L1324) with the maximum inhibition zones. The MICs of ethyl acetate and methanol extracts were obtained 31.25 and 62.5 μg/ml, respectively. The final weight gain of L. rohita was obtained 28.21±0.51, 31.33±0.76, 40.05±0.76, and 34.82±0.51 g in the treatments T1, T2, T3, and T4, respectively. The growth of ethyl acetate extracts-fed fish were significantly (p < 0.05) higher compared to the control. The specific growth rate was also found significantly higher in the T3, T4, and T2 relative to control. The fish fed garlic extracts enriched feed at 12.5, and 25 mg/kg developed resistance against MAS, while all the control fish died with expressions of distinct disease symptoms. Therefore, garlic ethyl acetate extracts could be used for growth enhancement and prevention of MAS in L. rohita.
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This study examined the Nile tilapia (Oreochromis niloticus) to determine the presence of Streptococcus agalactiae bacteria in three different sites. Isolates were identified, and gene sequences revealed four strains (accession numbers OL471406, OL471407, OL471408, and OL470978). The four strains harbored different virulence genes, and the most virulent strain was used in the treatment trial. The antibiotic of choice was florfenicol (FFC) for the isolate (minimum inhibitory concentration, 12 µg/g body weight, b.w.) and the median lethal dose of S. agalactiae was determined to be 0.3 × 105 CFU/mL. Experimental infection propagated the same clinical signs and post-mortem close to those obtained in the natural infection. Spirulina platensis at a concentration of 5 g/kg b.w. ameliorated the impact of FFC (12 and 1200 µg/k b.w.). A high dose of FFC could minimize the presence of carrier fish, but with deleterious effects on the immunity, which could be boosted by dietary S. platensis. Therefore, S. agalactiae could be confirmed to be associated with a high isolation rate in freshwater fish farms. A 100-fold of the minimum inhibitory concentration (MIC) in FFC could eliminate carriers and minimize coherent infection; thus, the addition of S. platensis to the medicated diet of O. niloticus is recommended to enhance the therapeutic efficacy by improving the immune responses of fish.
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The increasing demand for fish consumption has promoted the rapid development of fish aquaculture. With the continuous expansion of culture scale and the deterioration of culture environment, various diseases have broken out frequently, leading to huge economic losses to fish farming. Antibiotics and chemicals are common options to prevent and control of fish diseases, but their use is now restricted or even banned due to serious problems such as drug residues, pathogen resistance, and environmental pollution. Herbs and their extracts have increasingly become promising supplements and alternatives, because of their effectiveness, safety, environmental friendliness and less drug resistance. The application of herbal medicines in prevention and control of fish diseases is mainly attributed to the powerful immune enhancement, antioxidant or direct anti-pathogenic efficacies of their effective components, including mainly polyphenols, polysaccharides, saponins, flavonoids, alkaloids, and essential oils. Recently these herbal active ingredients have been extensively studied for their efficacies in prevention and control of viral, bacterial, parasitic, and fungal diseases in fish. In the present paper, we comprehensively summarize the research progress of the active ingredients of herbal medicines used for prevention and control of fish diseases, especially of their action mechanisms, and highlight the potential application of the herbal medicines in fish aquaculture.
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In the current study, growth performance, biochemical constituents of muscle, activities of enzymes in the haemolymph, and expressions of immune‐related genes were evaluated in the giant freshwater prawns Macrobrachium rosenbergii fed diets supplemented with aqueous garlic (Allium sativum) extract at 0, 5, 10 and 20 g/kg (w/w) for 60 days. At the end of the feeding trial, weight gain and specific growth rate were significantly improved in garlic‐fed prawn groups compared with the control (p < 0.05). Moreover, feed conversion ratio was significantly lower in the garlic‐fed groups than in the control (p < 0.05). Activities of catalase, superoxide dismutase and glutathione peroxidase in the hepatopancreas, activities of alanine aminotransferase, aspartate aminotransferase and levels of albumin and total protein in the hemolymph were significantly increased in the garlic treatments (p < 0.05). Furthermore, garlic supplemented diets improved muscle biochemical profiles, particularly contents of crude protein and total ash and upregulations of immune deficiency and heat shock proteins (HSP70) gene expression (p < 0.05). Therefore, garlic has positive effects on growth performance and physio‐biochemical responses of M. rosenbergii, and thus, it can be used as an additive for stress resistance and as a growth promoter in sustainable aquaculture.
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In this study, the dietary effect of garlic powder (GP) as an herbal supplement on the growth performance, digestive enzymes, innate immunity, and antioxidant capacity of narrow-clawed crayfish, Postantacus leptodactylus, was investigated. In a 90-day feeding trial, the crayfish (N = 360; 25.90 ± 0.41 g initial weight) were fed with a basal diet (control; GP-free) and supplemented diets with three levels of GP (0.5%, 1%, and 2%). The highest final weight and specific growth rate were obtained in the crayfish fed with GP at 1% and 2% (P < 0.05) and the weight gain in GP 2% treatment was 1.6 fold more than the control group. Also, the feed conversion rate and protein efficiency rate were improved in the GP-add groups compared to the control group (P < 0.05). Furthermore, the highest counts of total hemocyte, large-granular cell, and semi-granular cell were recorded in those fed with GP 2% diet. The crayfish fed GP 2% diet showed the highest and lowest body crude lipid (0.24 ± 0.03%) and protein contents (15.95 ± 0.12%), respectively. The highest protease (1.92 ± 0.03 U/ml) and amylase (8.36 ± 0.3 U/ml) activities were detected in the crayfish hepatopancreas fed with GP at 2% (P < 0.05). The highest lysozyme activity (21.26 ± 2.08 U/ml) was observed in the group fed with GP 2% diet, which showed a significant difference from others. Besides, total plasma protein and phenoloxidase activity in the groups fed with GP 1% and GP 2% diets were significantly higher than the control group. Moreover, the activities of superoxide dismutase (79.30 ± 2.19 U/ml) and nitric oxide synthase (4.16 ± 0.05 U/ml) in the plasma were significantly increased in GP 2% diet with respect to the GP 0.5% and control groups (P < 0.05). These findings confirmed the beneficial effects of dietary GP, especially at 2%, on growth rate, physiological performance, innate immunity, and antioxidant capacity in P. leptodactylus.
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Fruits and vegetables (FVs) have long been a major source of nutrients and dietary phytochemicals with outstanding physiological properties that are essential for protecting humans from chronic diseases. Moreover, the growing demand of consumers for nutritious and healthy foods is greatly promoting the increased intake of FVs. Allium (Alliaceae) is a perennial bulb plant genus of the Liliaceae family. They are customarily utilized as vegetable, medicinal, and ornamental plants and have an important role in agriculture, aquaculture, and the pharmaceutical industry. Allium plants produce abundant secondary metabolites, such as organosulfur compounds, flavonoids, phenols, saponins, alkaloids, and polysaccharides. Accordingly, Allium plants possess a variety of nutritional, biological, and health-promoting properties, including antimicrobial, antioxidant, antitumor, immunoregulatory, antidiabetic, and anti-inflammatory effects. This review aims to highlight the advances in the research on the bioactive components, physiological activities and clinical trials, toxicological assessment for safety, and applications of different Allium plants. It also aims to cover the direction of future research on the Allium genus. This review is expected to provide theoretical reference for the comprehensive development and utilization of Allium plants in the fields of functional foods, medicine, and cosmetics.
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The purpose of the study was to evaluate the effectiveness of garlic powder on lipid metabolism and the activities of antioxidative enzymes while treated with various lipids containing diet in hamsters. Thirty eight-week old hamsters were divided into five groups and fed with 15% dietary lipids and 0.1% cholesterol containing diet. The control group (S group) was given soy oil without garlic powder, other groups were added 3% garlic powder and various lipids such as soy oil (SG group), lard (LG group), fish oil (FG group) and canola oil (CG group). After 6 weeks, the animals were scarified. The lipids profile of plasma, livers and feces and the serum antioxidative status were also determined. Comparing each garlic subgroup, the LG group had the highest plasma total cholesterol, phospholipid, total lipids, low density lipoprotein-cholesterol (LDL-C), TG, very low density lipoprotein- triglyceride (VLDL-TG), LDL-TG and liver total lipids than other groups (P < 0.05), but no significantly differences with S group. The LG group, SG group and CG group showed the higher liver total cholesterol than the FG group (P < 0.05). The activities of plasma glutamateoxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT) showed no significantly differences. All garlic groups exhibited an increase in the excretion of total bile acids in feces, and an inhibition in the accumulation of total cholesterol, phospholipids, and triglycerides (TG) in liver as compared to the control group. Hamsters consumed garlic powder showed higher plasma total antioxidative status (TAS), less activities of plasma glutamic-pyruvic transaminase (GPT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and lower liver lipid peroxides (TBARS). Garlic powder affected the lipid metabolism and antioxidative status while hamster fed with various lipids-containing diets. Garlic powder consumption may decrease the accumulation of lipids in liver, increase the excretion of total bile acids in feces, and higher the antioxidative capacity while hamsters fed with various lipids-containing diets.
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This study investigated effects of various concentrations of garlic extract (0, 2, 4, 8, 16, and 32 mg/L) on hatching rate, growth and survival of larvae and juveniles, metamorphosis, and disease prevention for Manila clam Ruditapes philippinarum. The results showed that the hatching rate decreased with increasing concentrations of garlic extract. A garlic extract concentration of 16 mg/L resulted in delayed embryo development, and 32 mg/L resulted in hatching failure of the embryos. During the planktonic stage, larval growth was depressed by garlic extract; larval survival and metamorphosis increased and then decreased as garlic extract concentrations increased. A garlic extract concentration of 16 mg/L appeared to be optimal for larval metamorphosis and survival. The metamorphosis size decreased with increasing garlic extract concentrations. During the indoor rearing period, the growth and survival of juveniles also increased and then decreased as garlic extract concentrations increased, with 8 mg/L being the optimum concentration. Results from the present study demonstrated that garlic extract concentrations of 8 -10 mg/L could prevent diseases in the hatchery.
Article
The influence of environmental conditions and genotype x environment effects on the alliin content of garlic bulbs were studied. The objective was to improve the quality of garlic bulbs with regard to alliin content. Field trials were carried out for 2 years in France and Spain with increasing sulphur fertilisation in soil: 0-50-100-200 or 400 kg SO4/ha were investigated on 3 varieties in 2000 ('Printanor', 'Messidrôme' and 'Morasol') and only on 'Printanor' in 2001. S fertilisation affected alliin content on 'Printanor' in France, but was not confirmed in Spain where alliin contents were 3 to 5 fold higher than in France. These results were correlated to the soil sulphur in the two areas as Spanish soil was always higher in water soluble and total sulphur than French soil. However, the influence of other factors could not be excluded. Experiments were also carried out in controlled conditions (in vitro and greenhouse) to study the influence of sulphur fertilisation combined to other environmental factors such as light, carbohydrate availability and temperature. A strong genotypic effect was confirmed in both controlled conditions with light spectral quality having a large effect on alliin content on the in vitro bulbs. Temperature did not have a large effect on allying, but did interact with sucrose concentration to affect alliin accumulation in the bulbs. We also found an interaction between S fertilisation and genotype in greenhouse, and genotype by light spectrum interaction, in vitro. Our results confirm that multiple factors affect alliin accumulation in garlic, and that these factors should be considered when growing garlic for flavour or therapeutic value.