The Effects of Increasing Levels of Yeast Culture (Levucel SB) in a High Fibre-Diet on the Performance and Nutrient Retention of Broiler Chicks
One hundred and sixty (160) one day old Ross 355 broiler
chicks were used in an experiment to determine the effects of supplementing
brewer`s dried grain with Levucel SB yeast. Four experimental diets were
used. Diet 1 which served as control had 0.0 mg kg-1 dietary
inclusion level of yeast. Diets 2, 3 and 4 which had higher level of brewer`s
dried grain were supplemented with 200, 250 and 300 mg of yeast per kg
of diet respectively. Feed and water were supplied ad libitum.
The experiment lasted for four weeks. Results at the end of the experiment
showed that, feed intakes were not significantly affected by yeast supplementation.
However, live weight gains and feed conversion ratios of broilers fed
diets with yeast supplementation were significantly improved (p<0.05).
Cost of feeding to 4 weeks of age was also significantly reduced for these
groups of broilers (p<0.05). Dietary yeast supplementation did not
affect broiler livability. Results of nutrient retention trial showed
that while protein and fat retentions were comparable among broilers in
all groups whereas fibre retention was significantly increased by yeast
supplementation (p<0.05). It was concluded that, Levucel SB yeast fed
at either 250 or 300 mg kg-1 to supplement 26% inclusion of
brewer`s dried grain in broiler starter diet could enhance body weight
gain, feed conversion and fibre retention. In addition, such supplementation
could also result in lowering cost of feeding.
Protein and energy components of broiler starter ration are high. With
the use of traditionally costly feed ingredients such as maize and soybean
meal, the cost of producing starter ration also becomes high. Costs of
feeding broilers could be reduced with the use of less costly feed ingredients
such as industrial by products. One of such by products is brewer`s dried
grain. Brewer`s dried grain is high in metabolisable energy and crude
protein and hence could be used to reduce quantity of maize and soybean
used in broiler ration. Brewer`s dried grain usage is however limited
in monogastric animals because of its high fibre (24% ADF) content, so
it is not normally used in intensive feeding system.
Chickens are monogastrics and do not possess the enzymes needed to digest
high fibre diets. For this reason, it has been difficult and uneconomical
to substitute very cheap high fibre ingredients like rice bran, wheat
offal and brewer`s dried grain for the regular ingredients like maize
which are relatively costly.
Helping the chicken to extract more nutrients from feedstuffs is not
new. Atteh and Leeson (1985) showed that supplementary cholic acid enhanced
fat retention in broiler chicks fed diets high in saturated fatty acids.
Several researchers found benefits in the use of yeast (Onifade et
al., 1999; Onifade, 1997; Bradley et al., 1994), amino acids
(Braude et al., 1972), herbs and herbal extracts/green feeds (Best,
2000) in their feed formulations. In broiler and swine rations, the use
of appropriate feed additives offers an opportunity to overcome some of
these potential limitations imposed by exclusively vegetable protein-based
diets which tend to contain more fibre than animal protein sources and
poultry are known to be poor in digesting fibre (Longstaff and McNab,
1989). Yeast (Saccharomyces cerevisiae) has been traditionally
used as growth promoters in poultry and other animals. Various researches
on yeast have indicated that supplementation of yeast in diet is effective
in improving growth and feed efficiency in broilers. Yeasts primarily
targeted at grain or grain by-product components of the diets will have
both direct and indirect benefits on the digestibility of vegetable proteins
and fibrous matter in the ration. Indirect benefits can arise when yeasts
and metabolic enzymes breakdown the fibrous and nutrient components of
the ration (Adejumo et al., 2005).
Adejumo et al. (2005) reported that yeast supplementation at the
starter phase is more effective for promoting feed conversion and body
weight gain than that applied at the finisher phase of broiler production.
However, only two levels of supplementation 50 and 100 mg kg-1
of diet were employed in their study. Raju et al. (2006) reported
that up to 200 mg yeast per kg of diet improved feed efficiency of broilers.
In an attempt to determine the optimum level of yeast supplementation,
this study was designed to investigate the effects of three different
levels of yeast supplemented brewer`s dried grain in broiler starter diets
on chicks` performance and nutrient retention. A positive effect could
help in reducing the cost of feeding broiler chicks during the starter
MATERIALS AND METHODS
One hundred and sixty, one day old Ross 355 broilers chicks of mixed
sex were housed in an electrically fitted battery brooder cage. Unit size
of cage was 3021 cm2 with each unit fitted with one 90 watts
bulb to provide the necessary warmth for brooding. The chicks were allocated
into four treatment groups each replicated four (4) times with 10 chicks
per replicate. The study was conducted when the average daily temperature
was about 32°C and tropical day length averaging 12 h. The study took
place at Benson Idahosa University Teaching and Research Farms where four
different broiler starter diets (diet 1, 2, 3 and 4) were formulated (Table
1) using the ingredients purchased from reputable dealers. Diet 1
which served as control did not contain yeast supplement whereas diets
2, 3 and 4 contained 200, 250 and 300 mg kg-1 of diet respectively.
The yeast used was Levucel SB, a commercial yeast culture (Saccharomyces
cerevisiae) manufactured by Agrimerica Inc. and Lallemand Inc. in
Illinois, USA. In diets 2, 3 and 4 brewer`s dried grain level was increased
to 26.03 kg as against 14.0 kg used in the control diet 1, resulting in
higher fibre contents in the former.
Chicks were divided into four treatment groups. Four trials were conducted
using 40 chicks per trial. In each trial, 10 chicks were allotted for
each treatment group. Feed and water were made available ad libitum
to broiler chicks throughout the four weeks of data collection. Data
on feed intake, body weight gain and mortality were taken at weekly intervals.
Finally at the end of 4 weeks live weights of broilers were taken.
A nutrient retention trial was carried out at the 3rd week using total
collection method. Quantities of feed consumed by broiler chicks in each
group were determined over 72 h. Fecal samples were also collected over
the same period. The fecal samples were dried in an oven at 80°C,
weighed and milled prior to chemical analysis. Proximate analyses of feed
and fecal samples were carried out using the method of AOAC (1990).
||Percentage composition and nutrient contents of broiler
starter diets used in the experiment
|*: Supplied kg-1 diet: Vitamin A (8000iu),
vitamin D3 (1,200iu), vitamin E (31iu), vitamin K3 KASTAB (2 mg),
vitamin B2 Nicotinic acid (10 mg), vitamin B5 Pantothenic acid (150
mg), Manganese (Mn) (80 mg), Zinc (Zn) (50 mg), Copper (Cu) (2 mg),
Iodine (I) (1.2 mg), Cobalt (Co) (2 mg), Selenium (Se) (0.1 mg)
The data collected were subjected to the analysis of variance as described
by Steel and Torrie (1980) for a completely randomized design. Significant
differences in means were separated using Duncan Multiple range test (Duncans,
RESULTS AND DISCUSSION
Table 2 shows the effect of yeast supplementation on
the feed intake, weight gain, feed to gain ratio, percentage mortality
and cost of feeding during starter phase. Results at the end of four weeks
showed that feed intakes among chicks were not significantly influenced
(p>0.05). However, live weight gains and feed conversion ratios of
chicks fed supplemental yeast were significantly increased (p<0.05).
Also, cost of feeding was significantly reduced for these groups of broilers
during the starter phase (p<0.05). Percentage mortality of chicks was
not significantly affected (p>0.05).
The results of the nutrient retention trial is as shown in Table
3. Crude protein and crude fat retentions were comparable among broiler
chicks irrespective of the level of yeast supplementation (p>0.05).
Crude fibre retention on the other hand was significantly increased among
chicks fed on yeast supplemented diets than those on zero supplementation
that is the control (p<0.05).
The results on performance indices of broiler chicks confirm the growth
promoting property of yeast in poultry. Ignacio (1995) reported that yeast
has been traditionally used as growth promoter in poultry and other animal
diets. The results in many ways agree with earlier works (Onifade, 1997;
Adejumo et al., 2005). Earlier workers attributed parts of the
growth promoting properties of yeast to its ability to stimulate feed
intake by improving palatability (Wallace and Newbold, 1992; Ignacio,
||Effect of yeast supplementation on the performance and
cost of feeding broilers (0-4 weeks)
|**Means within column carrying different superscripts
differ significantly (p<0.05)
||Effect of Yeast supplementation on nutrient retention
by broiler chicks
|Means within column carrying different superscripts
differ significantly (p<0.05)
In this study, yeast, especially at 250 and 300 mg kg-1 supplementation
at the starter phase promoted higher body weight gains and better efficiency
in nutrient utilization than the diet without yeast supplementation. This
was however without a significant effect on feed intake. Earlier published
results had shown similar trends. For example, Charlie (1998) reported
that supplementation of 2-3 g yeast kg-1 diets is effective
in improving growth and feed efficiency in broilers. Also, Adejumo et
al. (2005) reported that yeast supplementation at 100 mg kg-1
at the starter phase promoted body weight gain and feed conversion without
significant effect on feed intake. The Levucel yeast used in this study
is a yeast culture which is a complex mixture and extra cellular fermentation
metabolites (enzymes, vitamins, various nutrients and co factors). It
has been observed that the positive effects of yeast are more apparent
on nutrient retention (Raju et al., 2006). The nutrient retention
values in this study seem to confirm yeast as a performance enhance especially
that of protein. Also, the significant retention value of crude fibre
confirms yeast as possessing the ability to degrade fibrous materials
in poultry feeds. Ordinarily, poultry lacks the enzymes such as cellulases,
hemi cellulases and xylanases needed to digest high fibre diets. Presumably,
it thus appears that yeasts primarily targeted at grain or grain by-product
components of the diets will have both direct and indirect benefits on
the digestibility of vegetable proteins and fibrous matter in the ration.
Adejumo et al. (2005) reported that indirect benefits of yeasts
can arise when yeasts and metabolic enzymes breakdown the fibrous and
nutrient components of the ration.
Yeast inclusion in the starter diet especially at 300 mg kg-1
supplementation seems to promote livability of broiler chicks as evidenced
by zero mortality. This results agree with earlier workers. For example,
Raju et al.(2006) reported reduced mortality due to non specific
aetiology in broiler flocks with inclusion of yeast in their feed. Best
(2000) also reported that some plant extract exhibited antibacterial properties
when used as feed additives for pigs. Incidentally, the use of antibiotic
as a feed additive is currently being restricted, in such a situation,
yeast may offer an effective alternative.
The reduction in cost of feeding observed in this study showed that,
supplementary yeast aided fibre digestion and nutrient utilization of
cheap, high fibre brewer`s dried grain, making it an economical substitute
for the costly, scarce, high energy maize in broiler starter diet. Charlie
(1998) on cost analysis for broiler production stated that when birds
were fed with high protein diets, the extra value of the birds receiving
yeast culture equaled $ 0.3959 resulting in 9:1 returns on investment.
In conclusion, Levucel SB yeast culture offers a number of potential
advantages as a feed supplement for broilers during the starter phase
as demonstrated in this study. Its inclusion at either 250 or 300 mg kg-1
dietary levels will enhance weight gain and feed conversion ratio as well
as reduce cost of feeding. Therefore, it is recommended that Levucel SB
yeast as used in this study could be added as a feed supplement when high
fibre diet is formulated for broiler chicks.
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