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Research Article
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Comparison of Broiler Performance and Carcass Parameters When Fed Diets Containing a Probiotic, an Organic Acid or Antibiotic Growth Promoter
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Ali Khosravi,
Fathollah Boldaji,
Behrouz Dastar
and
Saeed Hasani
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ABSTRACT
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This study was conducted to compare the broiler performance and carcass measurements fed diets containing a probiotic and an organic acid with those fed a diet containing antibiotic. In a completely randomized design, 320 commercial broilers were assigned to four dietary treatments. A control negative diet was prepared based on NRC recommendations. For preparing other diets, control diet was supplemented with a probiotic, propionic acid and an antibiotic (positive control) at the levels of 0.1, 2 and 1 g kg-1 of diet, respectively. Metabolic body weight and feed intake were recorded on days 14, 28 and 42. At the day 43, one male chicken from each pen was randomly selected and killed for determining the carcass parameters. Metabolic weight gain just was significantly increased during the first 2 week by propionic acid. The birds fed probiotic and propionic acid, either significantly or numerically, had better feed efficiency and lower metabolic feed intake than negative control. Thigh, breast, abdominal fat and carcass yields were unaffected by probiotic and propionic acid compared to negative control birds. No significant differences were observed in viability index among experimental groups. Although there were significant differences in performance index among the negative control group and those supplemented by propionic acid and probiotic groups during the first and the second 2 week, this difference just remained significant for propionic acid during the second 2 week. In conclusion, probiotic and especially propionic acid have potential to be used as suitable alternatives to antibiotic growth promoters in starter phase of broilers nutrition.
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Received: August 03, 2011;
Accepted: December 05, 2011;
Published: January 19, 2012
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INTRODUCTION
Antibiotic Growth Promoters (AGPS) have been used in the poultry
industry since about 50 years ago to improve poultry performance. However, the
use of AGPS in the poultry industry is completely being removed because
of their potential effects on humans and the environment (Boxall
et al., 2003; Rooklidge, 2004). Nowadays,
with the exclusion of AGPS in different parts of the world, there
is widespread concern that the removal of these feed additives will be negatively
affected poultry industry. It is, therefore, of interest to look for alternatives
to decrease the growth of harmful bacteria and to increase poultry performance.
Probiotics and organic acids are two of several feed additives that seem to
have a potential for reducing enteric diseases and for improving performance.
Organic acids have been used extensively in recent years and are capable of
reducing colonization of some opportunistic microorganisms, particularly Salmonella,
in the gastrointestinal tract and in the feces by changing the bowel pH (Heres
et al., 2004). It is reported that organic acids can improve nutrient
absorption (Boling et al., 2000) by controlling
intestinal microbial growth (Davidson, 2001; Chaveerach
et al., 2004), resulting better growth performance and feed conversion
ratio.
In the other hand, probiotics are microorganisms capable of adjusting the gastrointestinal
environment to the benefit of health status and of improving feed efficiency
Dierck (1989). Although, the actual modes of action
of probiotics in broiler chicks are not clearly understood, the recommended
modes mainly includes: removal of harmful microbial such as Salmonella
and Campylobacter by competitive exclusion (Jin et
al., 1998; Line et al., 1998; Nisbet,
1998; Netherwood et al., 1999; Fritts
et al., 2000), improving feed intake and the digestion of nutrients
altering metabolism by increasing digestive enzyme activity and decreasing bacterial
enzyme activity and ammonia production (Jin et al.,
1997) and stimulating the immune system (Gibson and
Fuller, 2000; Rolfe, 2000).
Although, there is a growing number of letters investigated the effects of dietary inclusion of these feed additives on poultry diets, fewer studies compared the efficiency of probiotics and organic acids as an alternative for AGPs. Therefore, the present study was conducted to compare the broiler chicken performance and carcass measurements when fed diets containing a probiotic and an organic acid with those of broilers fed diet containing a conventional antibiotic growth promoter. MATERIALS AND METHODS
Animals and diets: Four replicate groups, each consisting of 16 unsexed
1-d-old broiler chickens (Cobb, 500), were randomly assigned to four dietary
treatment groups and reared on floor pens for 42 days. A control corn-soybean
based diet (Table 1) was prepared based on National Research
Council recommendations (negative control) in 1994. For preparing other treatments,
the control diet was supplemented with a commercially probiotic (protexin, consisting
Lactobacillus acidophilus, L. bulgaricus, L. plantarum,
L. rhamnosus, Bifidobacterium bifidum, Candida pintolopesii,
Enterococcus faecium, Aspergillus oryzae and Streptococcus
thermophilus with minimum 2x109 CFU g-1 powder, obtained
from Nikotech Inc., Tehran, Iran), propionic acid (Merck, Germany, obtained
from Nemone Vasegh Inc., Gorgan, Iran) and flavomycin (positive control) as
0.1, 2 and 1 g kg-1 of diet, respectively. Propionic acid is a liquid
organic acid used in poultry nutrition which has about 4.97 kcal g-1
and the highest gross energy among the common organic acids (Kirchgessner
and Roth, 1991). No antibiotic and coccidiostat were added to water or diet
during the experiment. All chicks had ad libitum access to feeds and water.
The temperature of the room with continuous lighting was initially maintained
at 34°C and then it was reduced by 3°C week until it reached 18°C.
This temperature was maintained for the rest of the feeding period.
Experimental procedures
Metabolic Weight Gain (MWG) and Metabolic Feed Intake (MFI): MWG
and MFI were recorded on the 14, 28 and 42 days of the experiment. Initial body
weights were similar among the groups prior to diet allocation (average = 41
g bird-1).
Table 1: |
Composition of experimental (negative control) basal diet |
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*Premix contained 50% vitamin and 50% mineral premix that
contained or exceeded levels of recommended by the National Research Council
in 1994 |
Feed efficiency was calculated through dividing weight gain (g) by feed intake
(g). In calculation of feed conversion ratio, body weights of dead birds were
also considered.
Viability and performance index: The chickens were daily inspected and the number and the body weight of dead birds were registered. Mortality rates were calculated through dividing the number of dead birds by the total number of the birds and these rates were shown as percentage. Percentage of Viability Index (VI) and Performance Index (PI) of dietary treatments were measured using the following formula:
Sampling procedures for carcass analysis: At the end of the experiment (43 days of age), 20 male birds (1 bird per pen with 5 pens per treatment) the nearest to the mean weight of the pen, were randomly selected, weighed and killed for determination of the carcass characteristics. Then, determination of the thigh, breast, abdominal fat and carcass yield percentage (g kg-1 of BW) was performed.
Statistical analysis: Statistical analysis of data was performed using
Completely Randomized Design (CRD), in which the pens were signed as the experimental
units. Univariate analysis of variance was performed using General Linear Model
(GLM) procedures of SAS software (SAS, 2000). Differences
among treatments were separated using Duncan multiple range test at 0.05 probability
level.
RESULTS The effects of using probiotic, propionic acid and flavomycin on the MWG, MFI and feed efficiency of broiler chickens are shown in Table 2. MWG was increased (p<0.05) by propionic acid in the first 2 week period, whereas flavomycin resulted in a significant (p<0.05) increase in MWG during the third 2 week period of the experiment compared to the control diet. During the second 2 week period, MWG had no significantly difference among the groups. At the first 2 week, the birds fed diets inclusion of probiotic and propionic acid had significantly lower MFI than both negative and positive control. Birds fed control diet had significantly more MFI than the propionic acid diet in the second 2 week period. During the second 2 week, flavomycin and propionic acid made a significantly lower MFI compared to those fed control diet while no significant difference was observed using a diet supplemented with probiotic. There were no significant difference among the diets for MWG and MFI in the second and third 2 week, respectively. In the first 2 week period, the birds fed any feed additives had (p<0.05) better average feed efficiency than control and probiotic groups. Nevertheless, FI just improved (p<0.05) by supplementing propionic acid and flavomycin but not by supplementing protexin, compared to the control diet, in the second 2 week period. No significant difference was found between the birds fed control diet and those fed supplemental growth promoters in the third 2 week period.
The effects of dietary treatments on the percentage of the carcass components
are presented in Table 3. The thigh, breast and abdominal
fat yields of birds were unaffected by inclusion of any additives while the
birds fed a diet supplemented by flavomycin had higher carcass yield compared
to those fed by control and protexin diet (p<0.05).
Table 2: |
Mean (±SE) of control, probiotic, propionic acid and
flavomycin on performance of broiler chicks |
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a,b,cRow means with different superscripts differ
significantly at p<0.05. 1Probiotic. 2Propionic
acid |
Table 3: |
Mean (±SE) of control, probiotic, propionic acid and
flavomycin on percentage of carcass components of 6-week old broiler chicks |
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a,bRow means with different superscripts differ
significantly at p<0.05. 1Probiotic, 2Propionic
acid |
Although no significant difference was found in VI percent among the treatments,
there were a significant difference (p<0.05) in the PI between groups fed
any of the supplemental growth promoters in the first 2 week period compared
to the control group. In addition, the birds fed a diet inclusion of propionic
acid and flavomycin supplements had significantly better PI than control birds,
in the second 2 week.
DISCUSSION
Not only must a diet provide nutrient requirements of the bird but also must
regulate the bodys different function (Awad et
al., 2006) such as regulating gastrointestinal microbiota. Probiotics
and organic acids are capable of either facilitating or disturbing of the growth
of intestinal harmless or harmful bacteria, respectively. Undissociated form
of organic acids are capable of penetrating the membrane bacteria and of disturbing
their neutral pH (Eklund, 1983). Since bacteria have
to maintain an internal environment with a neutral pH, they have to frequently
transport excess protons from the interior of the cell, resulting a wasting
of cellular energy and finally killing the bacteria (Hinton
et al., 1990; Davidson, 2001). In addition,
organic acids can be absorbed in the distal end of the intestinal tract and
be metabolized as a substrate in the Krebs cycle (Hinton
et al., 1990; Hume et al., 1993) for
ATP production, providing an excess source of energy for growth purpose.
Reducing effects observed for performance among the birds fed diets supplemented
with propionic acid and probiotic with increasing birds age, suggesting that
the inclusion-timing of these additives alters their ability to have a significant
effects on broiler performance. Accordantly, Higgins et
al. (2010) observed that probiotic administration 24 h after Salmonella
enteritidis challenge provided no protection from enteric Salmonella
colonization, showing that the timing of the probiotic treatment is of affecting
factors for reducing cecal Salmonella incidence. These effects may be
related to the inability of young birds, especially during the first 15 days
of life, for producing of suitable levels of volatile fatty acids. Anaerobic
bacteria found in the intestinal microbiota of adult poultry produce volatile
fatty acids as a natural mechanism of host resistance to some bacteria (Corrier
et al., 1990; Van der Wielen et al., 2000).
Therefore, because young birds do not have suitable levels of this established
flora (Corrier et al., 1990), inclusion of diet
with organic acids and probiotic can reduce their sensitivity to pathogenic
bacterial infections. In addition, organic acids can reduce bufferic capacity
of diet, resulting a better protein digestion, especially in young animals having
low production of stomach acid (Kirchgessner and Roth, 1982).
It is noteworthy that the birds fed propionic acid diet had, either significantly
or numerically, lower metabolic feed intake than those fed control diet during
the throughout the experiment. This difference may be caused either by decreasing
in palatability of acidified diets because of their low tendency to absorb free
H+ ions and to have a strong taste (Cave, 1984).
Consistently, Donaldson et al. (1994) reported
decreased feed intake when 2 or 4% proprionate salts were given to newly hatched
turkey poults. The birds fed any of the supplemental growth promoters had better
feed efficiency during the first 2 week period and just propionic acid and flavomycin
supplementations during the following 2 week period. However, none of the supplements
significantly affected FE during the last period. The positive effects can be
due to the higher MWG, lower feed intake and/or the improvement of conditions
in the intestine that leads to improved digestion, absorption and better utilization
of nutrients (Parks et al., 2001; Fuller,
1999).
There are inconsistent results about the effects of feed additives on carcass
composition.
Table 4: |
Mean (±SE) of control, probiotic, propionic acid and
flavomycin on viability index and performance index of 6 week old broiler
chicks |
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a,b,cRow means with different superscripts differ
significantly at p<0.05. 1Probiotic, 2Propionic
acid, 3Viability index, 4Performance index |
Although, carcass trait is influenced by both genetics and the environment
at all stages from pre-hatch until the end of the commercial growing period
(Case et al., 2010), Cabel
and Waldroup (1991) reported that carcass efficiency and percentage of breast
meat are strongly affected by genetical factors and lightly affected by dietary
subjects ones. Therefore, since in the present study, we reported the carcass
parameters as a percent of MWG, the inclusion of probiotic and propionic acid
had any significant difference compared to negative control diet. In the case
of flavomycin, however, Visek (1978) founded the addition
of some antibiotics reduces the weight and length of the intestines in poultry
which has direct implications on carcass yield. No significant differences observed
for inclusion of probiotic and propionic acid, for carcass parameters in our
study was in agreement with result of Lesson et al.
(2005) who founded that the inclusion of 0.2% of butyric acid compared to
virginiamycin and control diets had any significant effect on carcass and breast
weights of broiler chicken. Additionally, Sacakli et
al. (2006) reported that the addition of 2.5 g organic acid had neither
significant effect on carcass weight (g) and nor carcass yield (%) of quails.
The results showed that dietary growth promoters had no significant effect
on the VI of broiler chicks (Table 4). No significant difference
observed for VI between the birds fed control diet with those fed feed additives
may be related to the environmental conditions of the experiment. In this study,
well-nourished and healthy chickens were kept in a good hygienic and suitable
stocking density environment resulted probably in a decreased efficacy of feed
additives. We think if the chickens were challenged orally with some pathogens
such as Salmonella, maybe viabilities were far from those achieved in
this study. Similar effects were found with broiler chicks were fed diets supplemented
with probiotics (Karaoglu and Durdag, 2005; Aftahi
et al., 2006). In the case of PI, all the chicks but not protexin
at the second 2 week, fed with growth promoters had better PI during the two
first 2 week period than the chicks of control group, due to their better feed
efficiency and MWG. In accordance with this result, other researchers observed
that inclusion of yoghurt and probiotic (Aftahi et al.,
2006) and different levels of lactic and citric acids (Abdel-Fattah
et al., 2008) as feed additives improved the PI of broiler chicks.
In conclusion, some results of this study demonstrated that probiotic and especially propionic acid have potential to be used as suitable alternative to AGPS in terms of some performances criteria, especially in starter phase of broilers nutrition. However, further studies are necessary to amplify the results of this experiment and to determine whether these results are likely to be applicable for other rearing conditions. ACKNOWLEDGMENT We thank Anvar Amozmehr for his special assistance in this experiment.
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