Download Effect of Different Growth Promoters on the Cecal Microflora and

461
Bulgarian Journal of Agricultural Science, 12 (2006), 461-474
National Centre for Agrarian Sciences
Effect of Different Growth Promoters on the Cecal
Microflora and Performance of Broiler Chickens
S. A. DENEV
TrakiaUniversity, Agricultural Faculty, BG-6000 Stara Zagora, Bulgaria
Abstract
DENEV, S. A., 2006. Effect of different growth promoters on the cecal microflora and
performance of broiler chickens. Bulg. J. Agric. Sci., 12: 461-474
The objective of this study was an evaluation of the effects of different growth promoters:
probiotic Lacto-Sacc® (Alltech, Inc. USA), nutritive premix Pharmastim and nutritive antibiotic
Avilamycin on the cecal microflora and performance of broiler chickens. The experiment was
conducted using four feeding groups of one-d-old broiler chicken: Group I: Basal diet without
supplement (Untreated control); Groups II, III and IV: Basal diet supplemented with probiotic
Lacto-Sacc®, (1.0 kg/t); nutritive premix Pharmastim, (0.3 kg/t); and nutritive antibiotic Avilamycin
(5,0 mg/kg), respectively. The addition of Lacto-Sacc® to the basal diet significantly increased
the count of lactobacilli and enterococci in the cecum of the broiler chickens and depressed the
count of coliforms by the low pH of cecal content. There was no significant difference in the
count of lactobacilli, enterococci, and coliforms present in the cecum of the untreated control,
Pharmastim and Avilamycin-fed groups. Lacto-Sacc® enhanced growth of beneficial microorganisms, regulated the microbial environment in the cecum. Lacto-Sacc® significantly increased
the body weight of broiler chickens (P<0.001), compared to the untreated control and the groups
fed Pharmastim and Avilamycin. The Lacto-Sacc®, Pharmastim and Avilamycin supplements
improved feed conversion ratio by 8.8, 1.1 and 1.9% (P<0.001), compared to the untreated control, respectively.
These results suggested that feed additives based on microorganisms provide an alternative
to antimicrobial substances in broiler nutrition. Probiotics, and especially Lacto-Sacc® can
reduce or replace antibiotics used for growth promotion in broiler chickens.
Key words: broilers, nutrition, cecal microflora, growth promoters, probiotics, antibiotics
Introduction
The microbial populations that inhabit the
gastrointestinal tract (GIT) of poultry have
been extensively studied in recent years
(Barrow, 1992; Chiang and Hsien, 1995;
Jin et al., 1996; Farran et al., 2004). Many
workers have studied the cecal microbial
This paper was presented as Poster: 1) At the Annual Meeting of the European Association for Animal
Production 2004 (EAAP-2004), 5-9 Sep., Bled, Slovenia, Book of Abstracts No 10 (Eds. A. Hofer and etc.),
Wageningen Academic Publishers, The Netherlands, pp 362. 2) At the 20th Alltech’s Annual Symposium
“Nutritional Biotechnology in the Feed and Food Industries” May 24-26, 2004, Lexington, Kentucky, USA.
Proceedings of the 20th Alltech’s Annual Symposium “Nutritional Biotechnology in the Feed and Food
Industries”, Suppl. 1., (Eds. T.P.Lyons and K. Jacques), pp.46.v
[email protected]
462
flora of the poultry. Several investigations
on indigenous microflora of chickens, laying hens, turkeys, pheasants, and ducks
have shown that the cecum contains the
largest number of resident obligate and
facultative anaerobic bacteria (Smith,
1965; Timms, 1968; Barnes and Impey,
1970, 1972; Barnes et al., 1972; Salanitro
et al., 1974a, 1974b) that perform a number of beneficial functions. The mechanisms whereby these bacteria are maintained in the cecum are poorly understood
(Barrow, 1992). Although many studies
have been carried out in the intestinal flora
of the bird and in particular the chicken,
one is still far from understanding the factors that govern the presence of particular groups of microorganisms in various
parts of the intestine and the role they may
play in the nutrition and physiology of the
bird.
Intensive rearing conditions for livestock are believed to contribute to a delay
or disturbance in the development of intestinal microflora. Chickens reared in
commercial hatcheries are never exposed
to bacteria from the mother hen and therefore the development of their intestinal
microflora is delayed. At hatching, the intestinal tract is essentially sterile, but it
becomes rapidly colonized by microorganisms from the environment (Stavric, 1994).
Several weeks are required to establish
an adult-type microflora in the cecum
(Smith, 1965). Nurmi and Rantala (1973)
recognized that the susceptibility of young
chickens to colonization with pathogens
was due to the delayed establishment of
their microflora.
The cecal microflora of the alimentary
tract has a significant effect on the health
and performance of poultry. There is considerable evidence that the cecal microflora exert protection against the establish-
S. A. Denev
ment of microbial pathogens such as Salmonella (Nurmi and Rantala, 1973) and
Campylobacter (Barrow, 1992), which
preferentially colonize the cecum.
It is well established that the manipulation of the gastrointestinal microflora
(GIM) of poultry has a significant effect
on the growth rate and efficiency of feed
utilization. However, the influences of antimicrobial agents on microbial population
of the cecum are less understood.
Antibiotics disturb the microbial balance
in the cecum. The sensitivity of chickens
to Salmonella infection increases after
antibiotic treatment (Stavric, 1994). Although antibiotics have been used as therapeutic agents and growth promoters since
the 1950s, there has been concern that their
usage as growth promoters could result in
the development of resistant populations
of bacteria, making subsequent therapy
with antibiotics difficult (Fuller, 1989; Skinner, 2003). Furthermore, consumers' concern regarding antibiotic residues in meat
has also been growing.
Because of the growing concern over
the transmission and the proliferation of
resistant zoonotic bacteria via the food
chain, the European Union (EU) decided
in 1999 to ban 4 commonly used antimicrobial growth promoters (AGP) (virginiamycin, spiramycin, tylosin, and zinc bacitracin). During 2003, the EU also
signalised its intention to remove the other
AGP by January 2006 (flavomycin and
avilamycin/monensin and salinomycin).
Currently, there are a number of nonantibiotic alternatives. Some of these alternatives may include significant changes
in husbandry practices or the strategic use
of probiotics, prebiotics, acidifiers, enzymes, herbal products, microflora enhancers, and immuno-modulators (Ferket,
2004).
Effect of Different Growth Promoters on the Cecal Microflora and Performance...
Modulation of the intestinal bacteria
towards a "healthy" community by feeding live bacteria (so called "probiotics") or
speciality carbohydrates supporting beneficial bacteria (so called "prebiotics") is
currently under active research (Apajalahti et al., 2004.). The target of such
nutraceutical products is to improve gastrointestinal health by selecting for beneficial microflora and suppressing known
intestinal and food-borne pathogens.
The interest in the use of probiotics as
substitute is not surprising, especially in
view of some claims that they offer a similar growth promoter benefit (Simon, 2003).
The main benefits attributed to probiotics
as natural feed additives are: restoration
and maintenance of the proper balance of
the microflora in the intestinal tract during
times of stress, diseases and following
antibiotic therapy. Probiotics act as natural growth promoters, and improve the
general health and performance of poultry (Dawson, 2001). Many reports and
reviews have shown that the oral administration of probiotics improve growth rate,
feed conversion (Jernigan et al., 1985;
Hussein and Ashry, 1991; Cho et al., 1992;
Baidya et al., 1993; Va Holourek, 1993;
Alvares et al., 1994; Manickan et al., 1994;
Chiang and Hsieh, 1995; Denev, 1996,
1997; Georgieva et al., 2000; Simon, 2003;
Skiner, 2003; Edens, 2003) and enhance
immune response and health (Perdigon et
al., 1995; Maasen et al., 2000; Sotirov et
al., 2000, 2001; Vitini et al., 2001 Denev,
2000, 2003). For the above reasons, there
is a wide interest in replacing AGP with
more natural feed additives - probiotics.
Although the cecum is an area of high
microbial activity in the intestine of chickens, the effects of such factors as a diet
on the cecal microflora is still not properly
understood, because a number of predomi-
463
nant anaerobic bacteria present have not
yet been isolated and characterized. There
is also little information available describing the predominant species of bacteria
occurring in the GIT of broiler chickens
fed different growth promoters, especially
nutritive antibiotics as well as probiotics.
The objective of the current study was
to examine the effect of probiotic LactoSacc®, a nutritive premix Pharmastim аnd
Avilamycin supplementation on the cecal
microflora and growth performance of
broiler chickens.
Materials and Methods
Chickens, Diet and Husbandry
Two hundred and forty-one-d-old female broiler chickens (Arbor Acres) supplied by a commercial broiler hatchery were
used in the current experiment. An environmentally controlled research building
with floor pens was used to house 60 birds
per pen (0.16 m2 per bird). Litter was new
pine wood shavings. Birds were randomly
assigned to treatment pens with empty
barrier pens between treatment pens. An
initial brooding temperature of 35oC was
maintained for the newly hatched chickens and reduced in weekly increments to
a constant temperature of 25oC at 3 weeks
of age. After that, environmental temperature and ventilation were regulated according to standard management practices for
bird age and external weather. Lighting
was continuous and feed and water were
provided ad libitum.
The chickens were divided into four
groups of 60 chickens each. During the
starter (0 to 28 d) and finisher (29 to 49 d)
periods, all groups were fed the basal
starter or finisher diets. The diet composition is presented in Table 1. We compared
four feeding groups: Group I: Basal diet
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without supplement (Untreated control);
Group II: Basal diet supplemented with
Lacto-Sacc® (Аlltech Inc., USA) (1.0
kg/t), contained per kg): Lactobacillus acidophilus (NLC 84), minimum 110 billion
(CFU); Streptococcus faecium (NCS 97),
minimum 77 billion CFU; Yeast culture Saccharomyces cerevisiaе, minimum.
1 980 billion cells, and enzymes; Group III:
Basal diet supplemented with Pharmastim
(Biovet, Bg), (0.3 kg/t), contained antibiotic Flavophospholipolum (Flavomycine) 2,0 and Excipiens ad 100.0), Group IV:
Basal diet supplemented with Avilamycin
(Elanco, USA) (5.0 mg/kg active substance).
Sampling procedures
At the end of the experimental period,
(49 d of age) five birds from each group
were randomly selected and killed by CO2
asphyxiation for collection of cecal contents. The intestinal tract was removed and
placed in a container under a flow of oxygen-free CO2. By using aseptic techniques,
both cecum with contents were ligated,
removed from the dissected body cavity,
and the contents were squeezed into a
beaker being flushed with CO2. The cecal
contents were collected aseptically, mixed,
while being flushed with CO2, before the
dilutions were made.
A pH-meter with a microelectrode
measured the pH of cecal contents from
each group. The test method was that used
by Barnes et al. (1979).
Microbiological analyses
Media. The count of viable microbes
in the cecal contents were determined
using various media: 1) The Anaerobic dilution solution (ADS) used in this work was
a modification of the dilution blank of
Holdeman and Moore (1977) containing
S. A. Denev
(g/l): K2HPO4 x 3H2O, 4.105; KH2PO4,
1.636; cysteine hydrochloride, 0.5; gelatin, 2.0; and resazurin, 1.0. The solution
was pre-reduced before use; 2) VLMH
Medium (Barnes and Impey, 1970), containing (g/l): tryptone, 10.0; NaCI, 5.0; beef
extract, 3.0; yeast extract, 5.0; cysteine
hydrochloride, 0.4; glucose, 2.5 (pH
7.2±0.2)) enriched with menadione (0.5
µg/ml) and hemin (5.0 µg/ml) and solidified with 1.5% agar (Schneitz et al., 1981)
was used to enumerate the total anaerobic and aerobic counts. The Anaerobic
dilution solution and VLMH Medium were
prepared from individual ingredients
(Merck, Germany); 3) Rogosa Agar
(Difco Laboratories, USA) was used for
enumeration of lactobacilli; 4) Slanetz and
Bartley Medium (Oxoid UK, CM377) was
used for enumeration of enterococci; 5)
MacConkey Agar (Difco Laboratories,
USA) for coliforms bacteria; 6) Bacto
Brilliant Green agar (Difco Laboratories,
USA) for Salmonella spp.
Enumeration Methods. Serial 10-fold
dilutions were prepared with sterile prereduced ADS. All dilution steps and inoculation of media were carried out under
anaerobic conditions according to procedures described by Moore and Holdeman
(1974). The serially diluted cecal contents
were used for the enumeration of the
anaerobic and facultative anaerobic organisms. All the plates used for the enumeration of the cecal microflora were freshly
prepared and poured a day before use,
pre-dried at 60oC for 15 minutes and stored
in the anaerobic conditions. The diluted
cecal contents were incorporated into
plates of VLMH Medium, Rogosa Agar,
Slanetz and Bartley Medium and
MacConkey's Agar, and Bacto Brilliant
Green agar to enumerate the total anaerobic and facultative anaerobic organisms,
Effect of Different Growth Promoters on the Cecal Microflora and Performance...
lactobacilli, enterococci, coliforms, and
Salmonella counts respectively. The
plates were incubated anaerobically in Gas
Pak® anaerobic system (BBL Microbiology Systems, Cockeysville, MD. USA.)
at 37oC for 5 days (Total anaerobic count);
at 37 oC for 48 h (lactobacilli and enterococci), and aerobically at 37oC for 24 h
(facultative aerobic count, coliforms and
Salmonella). The total colony counts per
g of undiluted cecal content from each medium were obtained as the weighed mean
from two or three highest duplicate dilutions that showed growth.
Performance data
During the 7 weeks experimental period, the following performance criteria
were studied: a) Live body weight (LBW)
was recorded individually before feeding
to the nearest 0.1 g at the beginning of the
trial (after hatching) and then to the nearest 0.01 kg at 1, 2, 3, 4, 5, 6, and 7 weeks
of age; b) Daily weight gain (DWG), kg;
c) Feed conversion ratio (FCR) was calculated on the basis of kg of feed/kg
weight gain.
Statistical analysis
All bacterial populations estimates were
calculated and reported on a per g (wet
weight) basis of cecal content. The mean
and standard deviation of the bacterial
counts (CFU/g) were calculated using
logarithmic values. Student's t-test, conducted using Microsoft Excel was used to
determine the significance of the differences between the experimental groups.
Results and Discussion
The composition of the cecal microflora of broiler chickens is shown in Table 1. The total viable count of obligate and
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facultative anaerobes in the cecal contents
was high in all experimental groups. These
bacteria formed the major part of the cecal flora. There was no significant difference in the total count of bacteria present
in the cecum of the control and experimental groups. Many other investigations
have shown that the cecum contains the
largest number of bacteria, most of which
are obligate and facultative anaerobes
(Barnes and Impey, 1970; Barnes et al.,
1972; Salanitro et al., 1978; Sofos et al.,
1985).
The results of the present study on the
bacterial counts of obligate and facultative anaerobes in cecal contents of broiler
chickens indicate also that Pharmastim
and Avilamycin have no inhibitory effect
on cecal microflora. According to Bare and
Wiseman (1964) the mechanisms that have
been proposed to explain the growth promoting effect of antibiotics usually involve
inhibition or stimulation of microorganisms
in the intestinal tract. Ilieva et al. (1997)
reported that the nutritive effect of Avilamycin is a result of its favorable effect on
the intestinal microflora.
Lactic acid bacteria, particularly lactobacilli, constitute an important group of microorganisms colonizing the GIT of chickens (Smith, 1965; Barnes, 1979). Mead
and Adams (1975) have shown that the
number of lactobacilli in the cecal tract of
young chickens increases during the first
14d from 510 to 910/g feces. Lactobacillus acidophilus, Lactobacillus salivarius
and Lactobacillus reuteri been shown to
be the most common species in the chicken
gut by Sara et al. (1985). The colonization
of the GIT by lactobacilli has long been
believed to promote health and productivity.
The experimental data obtained by the
microbiological analysis indicated that the
466
S. A. Denev
Table 1
Composition of basal starter and finisher diets
Ingredient, %
Maize
Soybean meal (41% CP* )
Sunflower meal (38% CP*)
Fish meal
Animal Fat
Vitamin mineral premix*
Sodium chloride
CaCO3
Dicalcium phosphate
DL-Methionine
Total:
Calculated nutrient content:
ME, MJ/kg
Crude protein, %
Lysine, %
Methionine + cystine, %
Calcium, %
Phosphorus (available), %
Starter
(To 28/d)
52.99
31.15
5.00
5.00
3.00
0.50
0.30
0.60
1.40
0.06
100.00
Finisher
(29 to 49/d)
61.89
24.35
5.00
3.00
3.00
0.50
0.30
0.60
1.30
0.06
100.00
3003.00
22.20
1.28
0.90
0.99
0.45
3085.00
18.82
1.01
0.75
0.90
0.40
Vitamin-mineral premix supplied the following vitamins and minerals per kg of diet: vitamin A, 200 000
IU; vitamin D3, 500 000 IU; vitamin E, 4 200 mg; vitamin K3, 400 mg; vitamin B1, 200 mg; vitamin B2, 1000
mg, vitamin B6, 400 mg; vitamin B12, 3 mg; vitamin PP, 5 000 mg; Calcium D-pantotenic acid, 2 000 mg;
Folic acid, 100 mg; Cholin chloride, 80 000 mg; Fe, 5 462 mg; Mn, 10 342 mg; Cu, 926 mg; Zn, 12 727 mg;
Co, 54,5 mg; I, 137 mg, and Se, 18,3 mg.
*
Lactobacillus population increased predominantly when broiler chickens consumed a diet supplemented with probiotic.
The results presented in Table 2 show
clearly that the lactobacilli were the most
numerous microorganisms present in the
cecum of broiler chicks receiving a basal
diet with the microbial supplement LactoSacc ® . Lacto-Sacc ® significantly increased the total number of lactobacilli in
the cecal content of broiler chicks
(P<0.001). Bonomi et al. (1995), and
Maruta et al. (1996) observed similar effects of Lacto-Sacc® (Paik et al., 1990)
and other directly fed microbials (Edens,
2003).
The counts of lactobacilli were significantly lower (P<0.001) in the cecal contents of the untreated control, Pharmastim
and Avilamycin-fed chickens. However, no
significant difference was observed in the
count of lactobacilli present in the cecum
467
Effect of Different Growth Promoters on the Cecal Microflora and Performance...
Table 2
®
Effect of Lacto-Sacc , Pharmastim and Avilamycin on the
cecal microflora broiler chickens*
Bacterial counts**
Total anaerobes
Facultative
Anaerobes
Lactobacilli
Enterococci
Coliforms
Salmonella
Untreated Control
a
Lacto-Sacc®
Pharmastim
a
Avilamycin
a
11.663±0.018
9.595±0.005a
11.533±0.250
9.485±0.015a
11.468±0.180 11.762±0.150a
9.433±0.016a 9.689±0.006a
6.878±0.003a
6.422±0.024a
5.826±0.006a
0
8.467±0.015b
7.039±0.035b
3.969±0.020b
0
6.764±0.069a
6.307±0.066a
5.656±0.012a
0
6.608±0.013a
6.460±0.176a
5.666±0.008a
0
*
Mean of five chickens ± SE of the mean.
** Log10/g (wet weight) of cecal contents
a – d: Different letters indicate significant differences (P < 0.001)
of the control, Pharmastim and Avilamycin-fed groups. These results indicated
that the above nutritive antibiotics do not
inhibit the population of Lactobacilli in the
cecal content of broiler chickens. Duta and
Devriese (1981) also reported that lactobacilli isolated from cecum of poultry are
resistant to some growth promoting
agents, particularly bacitracin, nitrovin,
carbadox, flavomycin, lincomycin, oleandomycin, spiramicin, and tylosin.
Enterococci form a significant part of
the intestinal flora of the bird throughout
life (Barnes et al., 1978). The results of
the present study (Table 2) indicate that
Lacto-Sacc® increases the number of enterococci population in the cecum of broiler
chickens. In the control, Pharmas-tim and
Avilamycin-treated groups, the number of
cecal Enterococci was significantly lower
in comparison with the Lacto-Sacc® - fed
chickens P <0.001). However, no observable significant difference in the counts of
Enterococci between the control, and
Pharmastim and Avilamycin-fed broiler
chickens were found.
One of the most important functions of
probiotics is the control or elimination of
enteropathogens (Fuller, 1989; Gibson et
al., 1997; Denev, 1996, 1977, 2000, 2003;
Edens, 2003). The mechanism by which
this occurs is still not well elucidated.
Among the suggestions that have been
considered are competition for limited carbon sources, and the production of antibacterial compounds (organic acids, hydrogen peroxide, bacteriocins).
The present study has shown that the
probiotic Lacto-Sacc® significantly decreased the number of coliforms in the
cecal content of broiler chicks compared
to the control, Pharmastim and Avilamycin-fed chicks (P<0.001). Chapman
(1989), Paik et al. (1990) and Bonomi et
al. (1995) have also reported that the addition of probiotics to the diet increased
the development and activity of intestinal
microflora, by increasing the number of
LAB, including lactobacilli and by decreasing the number of coliforms, particularly
E. coli. Many other investigators have
studied the potentials of probiotics, which
468
DWG was obtained by Gous (1990);
Wiseman (1990); McGinnis (1992),
Gippert et al. (1992), Gippert and Bodrogil
(1992); Samanta and Biswas (1995),
Wambeke et al. (1995); Vladimirova and
Sourdjiyska (1996); Edens (2003).
The LBW and DWG of Pharmastim,
and Avilamycin fed broiler chickens were
low and unaffected by treatment. The difference between groups with and without
nutritive antibiotics (untreated control) was
not significant. The results concerning the
effect of the nutritive antibiotic Avilamycin
that we obtained is different from the ones
reported by Jambos et al. (1995). Chapman
(1989) obtained similar results as the results achieved by us with other nutritive
antibiotics in comparison with probiotics.
Ayed et al. (2004) reported that Avilamycin decreases chicken growth performance and has undesirable side effect on
health.
The supplementation of probiotic Lac6.4
6.3
6.2
6.1
6
5.9
5.8
5.7
Avilamycin
Pharmastim
Lacto-Sacc
5.6
Control
Cecal pH
exert in vitro inhibitory effects toward enteric microorganisms (Gilliland and Speck,
1979; Edens, 2003) and in vivo growth
competition with E. coli in gnotobiotic
chickens (Watkins et al., 1982; Watkins
and Miller, 1983).
No cecal Salmonella was found from
birds fed the different supplements at 49
d of age (Table 2).
The inclusion of Lacto-Sacc® in the diet
of broiler chickens decreased significantly
(P<0.001) the pH of the cecal content in
comparison with the control, Pharmastim,
and Avilamycin-fed chickens (Figure 1).
The low pH produced in the cecum by the
probiotic microorganisms was partly responsible for the suppression of coliforms
in the cecum. The feeding of Lacto-Sacc®
may have greater significance in birds with
enteric disease caused by pathogenic E.
coli (Kovacz-Zomborszky et al., 1994).
Kumprecht et al. (1994) and Rada et al.
(1995) also reported that including probiotics in the poultry diet decreases pH in
the cecum. Similar results were observed
with the nutritive premix Pharmastim compared to the control (P 0.05). There was
no significant effect of Avilamycin on the
pH of the cecal contents in broiler chickens.
The effects of Lacto-Sacc®, Pharmastim and Avilamycin on broiler performance
are presented in Table 3. These data indicate that at the end of the experimental
period the probiotic Lacto-Sacc® had a
beneficial effect on growth performance.
It significantly increased the LBW and
DWG of broiler chickens (P<0.001). The
LBW of Lacto-Sacc® fed chicks were
7.5, 3.4, and 3.6 % higher in comparison
with the untreated control, Pharmastim and
Avilamycin fed chicks respectively. A
similar beneficial effect of Lacto-Sacc®
and other probiotics on poultry LBW and
S. A. Denev
Fig. 1. Effect of different supplements
on the cecal pH of broiler chickens
469
Effect of Different Growth Promoters on the Cecal Microflora and Performance...
to-Sacc® to the basal diet improved the
efficiency of feed conversion in comparison with the untreated control, Pharmastim
and Avilamycin fed broiler chickens (Table 3). During the experimental period, the
best feed conversion was appeared chickens fed Lacto-Sacc® (2.077 kg) which
needed 8.8% less feed for 1.0 kg weight
gain, in comparison with the untreated
control (2.277 kg). The differences among
the untreated control and other experimental groups were less - 1.1% (2.251 kg
Pharmastim supplemented) and 1.9%
(2.233 kg Avilamycin supplemented).
The better results in body growth and
feed efficiency obtained in the LactoSacc® fed chickens are most probably due
to the beneficial effect of this probiotic on
cecal microflora particularly on the Lactobacilli and the inhibition of enteropathogenic, and harmful bacteria. On the other
hand, Lacto-Sacc® contains some enzymes - amylase, protease, and cellulase
that improve digestibility and feed conversion of the diet.
Mortality was not affected by any of
the dietary treatment during the trial, which
is in agreement with Farran et al. (2004)
who used prebiotics, Avilamycin, Flavomycin, and Parks et al. (2001), who used
mannanoligosaccharides, Bambermy-cin
and Virginiamycin. Zulkifli et al. (2000)
when feeding broiler diets supplemented
with Lactobacillus spp. cultures or oxytetracycline reported similar lack of effect on mortality. According to Wenk
(1990) and Edens (2003) feed additives
based on microorganisms provide an alternative to antimicrobial growth promoters in animal nutrition. The probiotics can
reduce or replace antibiotics used for
growth promotion in broiler chickens.
The present study demonstrated that
Lacto-Sacc® enhanced growth of beneficial microorganisms and regulated the microbial environment in the cecum of broilers. This probiotic significantly increased
the number of lactobacilli and enterococci
and depressed the number of coliforms
and Salmonella spp. by the low pH of ce-
Table 3
Effect of Lacto-Sacc®, Pharmastim and Avilamycin on broiler performance*
Day
Control
Lacto-Sacc
®
Pharmastim
Avilamycin
Live body weight, g
1
7
28
38.08
37.73
103.00±2.00a
110.00±1.90a
818.00±8.60a
37.88
38.08
100.00±2.05a
99.00±1.72a
897.00±11.78b
836.00±16.30a
811.00±8.20a
42
1494.00±13.88a 1560.00±15.47b
1479.00±22.49a
1435.00±12.29c
49
1875.00±20.56a
1810.00±28.76a
1807.00±15.19a
2016.00±21.48b
Feed conversion ratio, g feed/g gain
**
1-28
28-49
1.970 (100)
2.501 (100)
1.769 (89.8)
2.315 (92.6)
1.894 (96.1)
2.543 (101.7)
1.949 (98.9)
2.454 (98.1)
1-49
2.277 (100)
2.077 (91.2)
2.251 (98.9)
2.233 (98.1)
* - Georgieva et al. (2000); ** - (% ; a – d: Different letters indicate significant differences (P < 0.001)
470
cal content. There was no significant difference in the number of lactobacilli, enterococci, and coliforms present in the
cecum of the untreated control, Pharmastim, and Avilamycin-fed groups. LactoSacc® significantly increased the LBW of
broiler chicks by 7.5; 3.4 and 3.6 % respectively - compared to the untreated
control and the groups fed Pharmastim
and Avilamycin. The Lacto-Sacc ® ,
Pharmastim and Avilamycin supplements
improved feed conversion by 8.8; 1.1 and
1.9% (compared to the untreated control),
respectively. These results suggested that
feed additives based on microorganisms
provide an alternative to antimicrobial substances in poultry nutrition. The probiotic
Lacto-Sacc® can reduce or replace antibiotics used for growth promotion in broiler
chickens.
Conclusions
The addition of probiotic Lacto-Sacc®
to the basal diet significantly increased the
count of lactobacilli and enterococci in the
cecum of the broiler chickens and depressed the count of coliforms by the low
pH of cecal content. There was no significant difference in the count of lactobacilli, enterococci, and coliforms present
in the cecum of the untreated control,
Pharmastim and Avilamycin-fed groups.
Lacto-Sacc® enhanced growth of beneficial microorganisms, regulated the microbial environment in the cecum.
Lacto-Sacc® significantly increased the
body weight of broiler chickens (P<0.001),
compared to the untreated control and the
groups fed Pharmastim and Avilamycin.
The Lacto-Sacc®, Pharmastim and Avilamycin supplements improved feed conversion ratio by 8.8, 1.1 and 1.9% (P<0.001),
S. A. Denev
compared to the untreated control, respectively.
These results suggested that feed additives based on microorganisms provide
an alternative to antimicrobial substances
in broiler nutrition. Probiotics, and especially Lacto-Sacc® can reduce or replace
antibiotics used for growth promotion in
broiler chickens.
Acknowledgements
The author express gratitude to L. Gati
(The Eastern European Director of
Alltech, Kft., Budapest, Hungary) for
supplying the Alltech's product LactoSacc®, to Lina Popova (MSc.), Department of Microbiology, Agricultural Faculty,
Trakia University, Stara Zagora 6000,
Bulgaria) for her excellent technical assistance, and to Prof. F. W. Edens (Department of Poultry Science, North Carolina State University, USA) for his constructive comments on the manuscript.
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