Effect of Narasin and Dietary Protein Source on Performance of Broiler
A factorial floor pen trail was conducted to study the
effects of formulating isonitrogenous and isoenergetic diets varying in
fish meal levels (0 and 50 g kg-1) with or without the ionophoric
anti-coccidial agent narasin (0 and 60 mg kg-1 of diet) on
performance of broiler chicks. Chick body weight, daily gain, feed intake
and feed conversion ratio were determined during experimental period.
The results indicated that body weight at 20 days, daily gain from 0-20
day, feed intake from 11-20 and 0-20 day were all significantly increased
with 50 g kg-1 fish meal inclusion in the diets. Narasin, on
the other hand, had no such effect and did not result in any interaction
with fish meal level on chick performance. These data demonstrated that
the beneficial effects of fish meal on broiler performances are mediated
mainly via improvement of feed consumption. These results also indicated
that under coccidial and necrotic enteritis free environment, narasin
growth promoter effect was insignificant (p>0.05).
Narasin is a mono-valent polyether ionophore (Greek: ioon = going; phoreo
= transport) that is a fermentation products of Streptomyces aureofaciens,
which is used in aid in the prevention of coccidiosis and necrotic enteritis
in broiler chicks (Branuius, 1985; Brennan et al., 2003; Chapman,
2001; Guneratne and Gard, 1991; Johansson et al., 2004).
Narasin has been by far the second most commonly used antimicrobial
in commercial poultry production, not only used for their anticoccidial
effect, but also as growth promoters in Eimeria-free environment, due
to their effect in improving feed conversion efficiency (Branuius, 1985;
Waldenstedt and Elwinger, 1995; Chapman, 2001; Johansson et al.,
2004). Brennan et al. (2001) showed that narasin is effective in
the preventions of necrotic enteritis (NE) in broiler chicks. Brennan
et al. (2003) also demonstrated the effectiveness of narasin fed alone
and in combination with bacitracin methylene disalicylate in the management
of necrotic enteritis using a Clostridium perfringens inoculum
challenge model. There is no doubt that the removal of antibiotic growth
promoters from animal feeds has resulted in a much higher rate of NE in
broiler flocks. Future plans to ban the use of coccidiostats will make
the situation further complicated. The poultry industry will have to learn
to cope with the new conditions, as they are learning to handle welfare
Fish meal is the most important conventional animal protein source for
poultry in most developing countries. It is fed to farm animals to improve
productivity, preserve health and welfare and to reduce dependence on
antibiotics and other drugs (Babu et al., 2005). It has been well
established that the beneficial effects of fish meal on broiler performances
are mediated mainly via improvement of palatability and hence broiler
daily feed intake (Karimi, 2006). In addition both fish oil and fish meal
provides a concentrated source of long-chain n-3 fatty acids, eicosapentaenoic
acid (C20:5, n-3, EPA) and docosahexaenoic acid (C22:6, n-3,DHA), which
has been showed to reduced the adverse affects of coccidiosis on growth
and reduced gut lesion scores in coccidiosis challenged chicks in the
absence of coccidiostats. These claimed effects of fish lipids on chicks
immune system is mainly postulated to mediate by moderating the immune
reaction to disease challenged and improving specific immunity (Bartov
and Jensen, 1980; Pike, 1999; Wiesenfeld, 2005). It has been showed that
when chicks were challenged with coccidiosis in the absence of coccidiostats,
incorporation of omega-3 fatty acids in the diet reduced the adverse effects
on growth and reduced gut lesion scores (Allen and Danforth, 1998). Increasing
demand, high costs and uncertain availability of fish meal, together with
risk factors associated with disease from animal protein sources, have
resulted in nutritionists studying alternative sources for inclusion into
the diets of poultry (Babu et al., 2005).
Whilst the potential of narasin as a valuable coccidiostat and effective
product in prevention of NE in broiler feeding is not in doubt (Watkins
and Bafudo, 1993; Conway et al., 2001), little research has been
done to determine whether animal protein sources with a potential contributing
to the outbreaks of clinical NE , such as fishmeal influence the broilers
response to narasin, in a coccidial free environment. Hence, to the best
of our knowledge, there is less information on the effects of narasin
and none on the interactions between protein source and narasin on broiler
performance, the objective of the study in this report was to examine
the performance response of broiler chickens to diets supplemented with
different levels of narasin in combination with dietary protein sources.
MATERIALS AND METHODS
The present study was carried out at the Animal Science Department of
University of Kurdistan, Kurdistan, Iran, during January to February 2006.
Three hundred and fifty two day-old, strait run, Hubbard broiler chicks,
were randomly allocated to four dietary treatments, each replicated four
times (22 chicks per pen) in a completely randomized design in a 2x2 factorial
arrangements. The chicks were housed in floor pens (1.2x1.5 m) using wood
shavings as bedding material throughout the experiment. Lighting was continuous
for the first day post-hatching, after which a 23L: 1D lighting schedule
was maintained for the duration of the experiment. Temperature was maintained
between 32 and 34 °C at the beginning of the rearing period and was
gradually decreased every 2 to 3 day to 22 °C at the end of rearing
period. Chicks were provided free access to feed and water during the
experimental period. Care and management of the chicks were in accordance
with commercial guidelines. The conditions and standards of care employed
in this study were approved by the ethical committee for animal experiments
of University of Kurdistan.
Dietary treatments: The corn-soybean meal-based starter (0-20
day) diets were formulated to meet or exceeded the requirements (NRC,
1994) for all nutrients. Experimental diets were formulated to contain
0 or 50 g kg-1 of fish meal. The ionophoric anticoccidial agent,
narasin supplement (with 0 or 60 mg kg-1 of the diet) was added
directly to the diets (Table 1).
Measurements: The experiment was conducted for 20 days. Birds
were weighed as a group on arrival. At 10 and 20 day, all birds were weighed
and feed intake was determined. Feed conversion was calculated after adjusting
for daily mortality. Average body weight, daily gain, feed intake and
feed to gain ratio (FCR) were calculated for each period and for the overall
|| Composition (%) and calculated analysis of basal diets
|1Treatments: A = Control (no fish meal, no
narasin); B = No fish meal, 60 mg kg-1 of narasin; C =
5% fish meal, no narasin; D = 5% fish meal and 60 mg kg-1
2Provides per kg of diet: Vit. A, 9000 IU;
Vit. D3, 2000 IU; Vit. E, 18 IU; Menadion, 2 mg; Thiamine, 1.8 mg;
Riboflavin, 6.6 mg; Niacin, 30 mg; Pyridoxin, 3 mg; Vit B12, 15 mcg;
D-Pantothenic acid, 100 mg; Folic acid, 1 mg; Biotin, 0.1 mg; Choline
chloride, 500 mg; Antioxidant, 100 mg
kg of diet: Manganese, 100 mg; Zinc, 84.7 mg; Iron, 50 mg; Copper,
10 mg; Iodine, 1 mg; Se, 0.2 mg
Data were analyzed according to General Linear Model (GLM) procedure
of SAS (2001) as a Completely Randomized Design (CRD) in a factorial arrangement.
Significant differences among treatments were determined at p<0.05
by Duncan`s new multiple range tests. Pen was used as the experimental
RESULTS AND DISCUSSION
During the experimental period mortality was within acceptable level
(less than 2%) and was not related to dietary treatments. The influences
of different dietary treatments on broiler performance are shown in Table
The results of this experiment showed that broiler liveweight at 10 day
and average daily gain during the 0-10 and 11-20 day periods were not
significantly influenced by 50 g kg-1 fishmeal inclusion to
the diets (p>0.05). However, the results indicated that chick body
weight at 20 day and average daily gain through experiment were significantly
improved (about 6%) with fishmeal supplementation to the diets (p<0.05).
The results also showed that daily feed intake was significantly (p<0.05)
increased by fishmeal level during the 11-20 and 0-20 day periods, but
no such effect was noted between 0-10 day (p>0.05). The results of
this experiment on the fish meal effects on broiler performances is consistent
with previous reports (El Boushy and van der Poel, 1994; Karimi, 2006)
in that the beneficial effects of fishmeal on broiler performances are
mediated mainly via improvements of diet palatability, which consequently
resulted in greater nutrient supply for chick growth. Many feed formulators
ensure a minimum incorporation of fish meal in poultry diets, based on
practical experience and experimental results indicating that this level
of fish meal produces increases in meat production and better feed utilization
compared with diets not containing fish meal. These minima are justified
when the income from the increased performance exceeds the cost of incorporating
these minimum levels in the diet. In addition it has been shown that dietary
fish meal may enhance the immune response in poultry, which prove useful
in infections in which cell-mediated immunity plays a role (Babu, 2005).
|| The effect of different fish meal level (%) and narasin
supplementation on performance in broiler chicks (Mean ± SD)
|a, b: Mean values within a row and under
each main effects with no common superscripts differ significantly
The results of this experiment also showed that supplementation of experimental
diets with coccidiostatic compound, narasin had no significant impact
on broiler performance (p>0.05). The lack of significant effects of
narasin on broiler performance in this study reconfirms the previous finding
that anticoccidial drugs have no effects on broiler performance in a relatively
coccidia-free environment. It must be noted that differences in exposure
to coccidial challenge by poultry might be a factor in the growth response
to polyether ionophorous compounds (Conway et al., 1999). Waldenstedt
et al. (1999) reported that inoculated broiler chicks with a mixture
of chicken Eimeria isolates had a 10% lower live weight than un-inoculated
chickens and the performance of un-inoculated birds was similar to that
of inoculated birds treated with narasin. Watson et al. (2005)
also showed that broiler chick`s daily gain, average feed intake and gain:
feed ratio was reduced by coccidial inoculation. It should be borne in
mind that nearly all anticoccidial drugs have no positive effects on final
body weight or even cause slight growth depression, even at the recommended
levels in the absence of coccidial exposure (Braunius, 1985; Radu et
al., 1987; Pesti et al., 1999).
In addition, lack of growth promoter effects of narasin in this study
might be partially due to the lower prevalence of C. perfringens
in birds given narasin in this study, since the birds were not inoculated
with Clostridium perfringens inoculums and kept in well disinfected
environment. Brennan et al. (2003) demonstrated that Bacitracin
Methylene Disalicylate (BMD) and narasin, fed alone and in combination,
are effective in reducing morbidity, mortality, NE lesion scores and suppression
of growth and feed efficiency associated with NE among broiler chickens
challenged with C. perfringens. Johansson et al. (2004)
in a comparative study of different antimicrobial drugs also demonstrated
that the narasin is still a potent antimicrobial agent against C. perfringens
and development of resistance is apparently slow.
The interaction between fishmeal and narasin supplementation on chicks
performance (Table 3) was not significant (p>0.05).
The growth and intake depressing effects of anticoccidials was the main
interest in this study, since it was hypothesized that these negative
effects may be partially overcome via the growth and feed intake stimulating
effects of fish meal. Given the lack of response to narasin fed in this
experiment, it is not surprising that there was no interaction with the
inclusion rate of fishmeal. One potential reason for this may be related
to the type of anticoccidial drug used in this study and the marginal
differences in protein and amino acids provided with our different dietary
treatments. Bartov and Jensen(1980) reported that monensin induced growth
depression was greater in birds fed on animal protein containing diets
than in those fed a corn-soybean diet, but Pesti et al. (1999)
showed that there were no significant interactions between protein source
and semduramicin on growth (all plant protein or 12% of the protein content
from animal origin). In conclusion, the results of the present experiment
showed that the beneficial effects of fishmeal on broiler performance
becomes most evident during the later stages of the early growth period
of broilers, mainly via stimulation of feed intake. The results indicated
that under condition of coccidial free environment, Narasin had no significant
effect on broiler chick`s performance during starter period and did not
result in any interaction with fish meal level.
|| The interaction effects of fish meal levels (%) and
narasin supplementation (with or without) on performance in broiler
chicks (Mean ± SD)
|a, b: Mean values within a row with no common
superscripts differ significantly (p<0.05)
We also gratefully acknowledge the valuable comments and suggestions
of Dr. Michael Bedford (Zymetrics Inc., Marlborough, UK ) and Dr. A. Kamyab
(Animal Science Res. Ctr., University of Missouri) during preparation
of this article.
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