Processed Cocoyam Tuber as Carbohydrate Source in the Diet of Juvenile African Catfish (Clarias Gariepinus)

European Journal of Scientific Research
ISSN 1450-216X Vol.35 No.3 (2009), pp.453-460
© EuroJournals Publishing, Inc. 2009
http://www.eurojournals.com/ejsr.htm


Processed Cocoyam Tuber as Carbohydrate Source in the Diet
of Juvenile African Catfish (Clarias Gariepinus)


Aderolu, Ademola Zaid
Corresponding Author, Department of Marine Sciences
University of Lagos, Akoka, Nigeria
E-mail: dezaid@yahoo.com
Tel: +2348033225139

Lawal Muyideen Owonire
Department of Marine Sciences, University of Lagos, Akoka, Nigeria

Oladipupo, Muinat Oluwakemi
Department of Marine Sciences, University of Lagos, Akoka, Nigeria


Abstract

One hundred and forty seven juveniles of Clarias gariepinus of mean weight
50.00g were randomly stocked at 7 juveniles per tank of dimension 52.5cm x 33.5cm x
21cm and fed six iso-nitrogenous diets containing graded level of raw and differently
processed cocoyam tuber at 25% and 50% substitution levels for maize meal over a period
of 56 days.
The result of the experimental treatment showed mean weight gain, relative growth
rate (RGR) and the specific growth rate (SGR) had the highest values recorded for the
control diet (72.3±2.67, 82.1±2.34 and 0.6±0.11), then 25% boiled cocoyam diet
(54.4±3.67,73.6±2.36 and 0.49±0.13) and the least values for the 50% fermented cocoyam
diet (24.0±1.32, 41.1±1.76 and 0.27±0.06). The best feed conversion ratio (FCR)
andprotein efficiency ratio (PER) were recorded for the control diet while the least values
were recorded for the 50% fermented diet. The boiled cocoyam when compared to the raw
and fermented cocoyam at both 25% and 50% level resulted in better mean weight gain,
FCR and PER. The highest feed cost ($1.144±0.07) was recorded for the control diet and as
observed cost of feed decreases with cocoyam inclusion level (0.98-1.00$).
Heamoglobin(Hb) and packed cell volume (PCV) increased as a result of processing of the
cocoyam meal, converse trend was observed for the lipid protein and cholesterol. All blood
parameters measured were significantly lower in the unprocessed cocoyam meal diet in
comparism to the control diet.


Keywords: Cocoyam, maize feed utilization, growth.

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Processed Cocoyam Tuber as Carbohydrate Source in the Diet of Juvenile
African Catfish (Clarias Gariepinus) 454

Introduction
Carbohydrates are used in fish diet primarily as energy source and for their binding properties. It can
be added in excess of the amount that can be efficiently utilized for energy by the fish (Krogdahl et al,
2005). Carbohydrates are important in formulated diets because they are cheaper than lipids and
protein and a knowledge of the optimal level of protein and protein sparing effect on dietary
carbohydrate may be useful in reducing the cost of fish feed.
Diets used in fish farming contain highly variable amounts of carbohydrates depending on the
cultivated species. Fish species differ greatly in their ability to digest carbohydrates; this variability
reflects anatomical and functional differences of the gastrointestinal tract and associated organs. Even
within fish species we find carbohydrate content of diets vary substantially.
Although grains and grain products are the main carbohydrate sources in the diets of cultivated
fishes and other livestocks {Darunna 2000}, an attempt at fulfilling the energy requirement of livestock
through the use of root and tubers could probably ameliorate the stiff competition with cereals and
grains (Agbede et al 2002). Furthermore to meet up with annual increase of fish production, research
should be targeted towards the use of alternative or unconventional feed ingredients such as root and
tubers which could probably improve the feed water stability and nutrient retention, increase efficiency
of digestibility and reduce cost of fish feed production (Falayi, et al., 2003 and 2004).
The production of cocoyam otherwise called Taro is low compared to the other roots and tubers
(Fagbenro and Adebayo, 2002) but its superiority in terms of digestibility of starch (98.8%), the size of
starch grain (1/10th of potato), the sulphur amino acid and price per tonne makes it a better choice than
cereals in fish feed production (Hahn 1984, Ezedinma 1987). Cocoyam has been found to contain
calcium oxalate crystal, phytate, tannins and saponins (Agwunobi et al 2002) which effect could be
minimize by boiling, baking and fermentation to make cocoyam an excellent source of carbohydrate,
vitamins and minerals.(Abdulrashid and Agwunobi 2009)
Clarias gariepinus (Burchell, 1822) is one of the most suitable aquaculture species in Africa.
This catfish has been credited for being hardy, resistance to handling stress, omnivorous, better growth
and feed conversion abilities (Eyo et al., 2004). The high quality and better taste of its flesh makes it a
highly demanded fish; hence there is a need to increase the local production of this species at cheaper
production cost (Sogbesan and Ugwumba 2008).
The aim of the present study was to evaluate the effect of substitution of maize with differently
processed cocoyam tuber on growth, nutrient utilization and economic benefits of C. gariepinus
juvenile.


Materials and Methods
Purchase and Processing of Feed Ingredients
The red cocoyam tuber (Colocasia spp.) used for this experiment was purchased from a local market
located at Bariga market, Lagos state, Nigeria. Enough quantity was purchased at the start of the
experiment to avoid problems associated with different batches of ingredients. Other feed ingredients
were purchased from Sabina Pad Nigeria Limited, opposite Lagos State Abattoir, Oko-Oba, Agege,
Lagos state, Nigeria.
Cocoyam tubers were peeled, sliced and divided into three different portions, the first portion
was washed and sundried,the second portion was boiled and sundried, while the third portion was
soaked for 4-5 days and then sundried for 3-4 days. Each of them were separated into different
polythene bags and labeled Raw(R), Boiled (B) and Fermented (F) respectively. Each portion of
processed cocoyam and other ingredients were ground separately into powder and stored for future use.
Graded levels of the differently processed cocoyam meals were substituted at 0% (control),
25% and 50% graded levels respectively for maize as shown in Table 1. Measured quantities of each
ingredient were mixed and blended together and thereafter compressed using a pelletizing machine to

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455
Aderolu, Ademola Zaid, Lawal Muyideen Owonire and Oladipupo, Muinat Oluwakemi
3mm size. It was then sundried to about 90% dry matter and stored for feeding.The seven diets are
shown in Table 1.

Table 1:
Feed composition of experimental diet (kg)

Diet 1
Diet 2
Diet 3
Diet 4
Diet 5
Diet 6
Diet 7
Diet
CWC
RC BC FC RC BC FC

25% 25% 25% 50% 50% 50%
Fish meal (72%)
25.0
25.0
25.0 25.0 25.0 25.0 25.0
SBM 35.6
35.6
35.6
35.6
35.6
35.6
35.6
Maize
35.0
26.2
26.2
26.2
17.4
17.4
17.4
Cocoyam
-
8.74
8.74
8.74
17.4
17.4
17.4
Methionine
0.25
0.25
0.25
0.25
0.25
0.25
0.25
Premix 0.40
0.40
0.40
0.40
0.40
0.40
0.40
Oil
1.50
1.50
1.50
1.50
1.50
1.50
1.50
Salt
0.25
0.25
0.25
0.25
0.25
0.25
0.25
DCP 2.0
2.0
2.0
2.0
2.0
2.0
2.0
Key:
CWC=Control without Cocoyam, RC = Raw Cocoyam,BC=Boiled Cocoyam, FC=Fermented Cocoyam,SBM =
Soybean meal , DCP=Dicalcium Phosphate

Values are the mean of triplicate groups of fish. Mean values with different letters in column
were significantly different in the Ducan test (p<0.5).

Experimental Fish, Water Supply and Feeding
One hundred and fourty seven juvenile of C. gariepinus were brought to the nutritional laboratory of
the Deparment of Marine Sciences, University of Lagos Nigeria, allow to acclimatise for a period of
two weeks before the commmencement of the experiment. Fish were randomly allocated on the basis
of body weight (50g) into twenty one plastic tanks (dimension 52.5cm x 33.5cm x 21cm) for the
growth trials. Before the commencement of the feeding trial fish were starved for 24 hours to empty
their gastro intestinal tract and each of the diets was fed thrice daily (9:00h, 1:00h and 17:00h) to
satiation. Excess feed was siphoned an hour after every feeding, dried and weighed to estimate the
actual feed intake per week. All the fish in each tank were weighed weekly interval after which the
mean body weight was determined and feed intake adjusted accordingly. At the end of the
experimental period, 2ml of blood was collected from the caudal peduncle of 2 fishes each per
experimental diet according to the method of Joshi et al., (2002a). The blood samples were then
dispensed into heparinised bottles to prevent coagulation. The capillary tubes were micro-centrifuged
to determine the percent hematocrit value and the hemoglobin (Joshi 2002a). Other blood parameters
measured from the decanted plasma included plasma protein and cholesterol.


Data Computation
The weight gain record and feed consumed were computed every 7days and later used to calculate the
growth, feed utilization and economic parameters.
Mean Weight Gain (g) = Mean Final Weight – Mean Initial Weight
Specific Growth Rate (SGR %/day) = (LogW2 - LogW1) x100 / T2 - T1,
where W2 and W1 = final and initial weight; T2 and T1 = final and initial time respectively.
Feed Conversion Ratio (FCR) = Feed fed (Dm) / Fish weight gain
Protein Efficiency Ratio (PER) = Mean weight gain per protein fed
Protein Intake (PI) = Feed intake x crude protein of feed.

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Processed Cocoyam Tuber as Carbohydrate Source in the Diet of Juvenile
African Catfish (Clarias Gariepinus) 456

Economic Estimates
Based on the price of each raw material ($) and the amounts that were required to make the different
diets, we calculated the cost/kg of each diet. The raw material prices used were average prices during
the experimental period, due to the fact that there may be significant changes throughout the year. The
economic conversion ratio (ECR) was determined using the following equation, ECR = Cost of diet x
Feed conversion ratio (Piedecausa et al., 2007).


Statistical Analysis
All the results were subjected to analysis of variance (ANOVA). Duncan multiple range test (Duncan,
1955) was used to evaluate the mean differences among individual diet at 0.05 significant level.


Results
The feed composition of experimental diets is shown in Table 1.The diets prepared from differently
processed cocoyam and maize were isocalorific and isonitrogenious.Mean intial weight of the
experimental fish were not significantly different (P>0.05) and no mortality was noticed throughout the
experimental period. The feeding trials revealed that C. gariepinus responded to all the diets, the mean
weight gain, relative growth rate (RGR) and the SGR had the highest value recorded on the control diet
(72.3±2.67, 82.1±2.34 and0.6±0.11), which is only next to the 25% boiled cocoyam diet (54.4±3.67,
73.6±2.36 and 0.49±0.13) and the least significant value was recorded on the 50% fermented cocoyam
diet (24.0±1.32,41.1±1.76 and 0.27±0.06). The best FCR and PER were recorded for the control diet
while the least value of FCR and PER were recorded for the 50% fermented diet. The boiled cocoyam
when compared to the raw and fermented cocoyam at both the 25% and 50% level had better mean
weight gain, FCR and PER. The highest feed cost (1.144±0.07) was recorded for the control diet and as
observed cost of feed decreases with cocoyam inclusion level (0.98-1.00$). Difference in cost of feed
was also noticed among diet within same inclusion level of cocoyam as a result of variation in method
of processing.Economic conversion ratio was lowest on control diet and highest on the 50% fermented
diet.While heamoglobin(Hb) and packed cell volume (PCV) increased as a result of processing of the
cocoyam,the converse was observed for the lipid protein and cholesterol. Between the 25% and 50%
diets,cholesterol was found to increase at higher level of cocoyam inclusion while the PCV decreased
along the same trend. All blood parameters measured were significantly lower in the unprocessed
cocoyam meal diets in comparism to the control diet.


Discussion
The nutritional quality of cocoyam meal as determined by growth and economic indices observed in
this study showed the adequacy of the diets at meeting the nutritional requirement of the fish under
study.This is evident as a result of no mortality and improved weight gain in all the experimental fish
during the feeding trial.
Processing conditions have great impact on starch digestibility (Allan et al 2000; Booth et al
2001). Beneficial effects of heat treatment are apparent even for the herbivorous fish (Erfanullah and
Jafri 1998). Processing conditions vary widely, and comprise dehulling, concentration, heat treatment
in pellet press or extrusion, heating under wet or dry conditions and fermentation among others. From
the study it may be concluded that starch treated with heat could be better digestibled by both
carnivorous and herbivorous species.

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457
Aderolu, Ademola Zaid, Lawal Muyideen Owonire and Oladipupo, Muinat Oluwakemi
Table 2:
Growth Performance and Nutrient Utilization of Clarias gariepinus Fish fed with Graded Levels of
Processed Cocoyam Tubers

Parameters
Control (1)
Diet 2
Diet 3
Diet 4
Diet 5
Diet 6
Diet 7
Mean 50.0+2.43a 50.1+1.93a 50.0+2.71a 50.2+1.37a 50.2+1.56a 50.0+1.74a 50.0+1.65a
initial
weight

Mean 122.3+3.94a 80.4+3.45b 104.4+4.67ab 99.7+2.57a 85.6+2.67ab 97.3+3.23ab 74.0+3.19b
final
weight


Mean 72.3+2.67a 30.3+1.89b 54.4+3.67ab 49.6+2.34ab 35.4+1.89ab 47.3+2.19ab 24.0+1.32b
weight

gain
Average 114.5+5.65 81.3+3.79 103.5+3.56 97.0+3.76 104.4+4.36 105.8+5.21 91.4+3.43
feed
intake
RGR 82.1+2.34a 48.5+2.47ab 73.6+2.36ab 71.0+2.04ab 54.7+2.32ab 70.0+3.21ab 41.1+1.76b
SGR 0.60+0.11a 0.32+0.09b 0.49+0.13ab 0.47+0.15ab 0.37+0.13ab 0.46+0.12ab 0.27+0.06b
FCR 1.76+0.08b 3.29+0.45ab 2.58+0.34ab 2.23+0.14b 3.03+0.56ab 2.21+0.23b 4.12+.82a
PER 0.017417+0.0023 0.00949+0.0015 0.01322+0.0065 0.1383+0.0078 0.00961+0.0006 0.1316+0.0075 0.007481+0.0016
FC ($)
1.144+0.07 1.096+0.05 1.116+0.06 1.110+0.063 0.980+0.047 1.000+0.052 0.986+0.043
ECR 2.013
3.606
2.879
2.475
2.969
2.210
4.151
Values are the mean of triplicate groups of fish. Mean values with different letters in column were significantly different in
the Ducan test (p<0.5).
Key:
Diet 1: Control
Diet 2: 25% Raw Cocoyam inclusion
Diet 3: 25% Boiled
Diet 4: 25% Fermented
Diet 5: 50% Raw
Diet 6: 50% Boiled
Diet 7: 50% Fermented, SGR= Specific Growth Rate, RGR =Relative Growth Rate, MWG= Mean Weight Gain,
FCR=Feed Conversion Ration, PER=Protein efficiency ratio. FC=Feed cost ($) and ECR=Economic
conversion ratio

Table 3:
Result of Blood Analysis

Haemoglobin
Packed Cell Volume
DIETS
Protein g/l
Cholesterol
(Hb)g/100ml
(PCV) (%)
Diet 1
11.7±1.89a
33.0±5.13b 55.8±4.11a
85.1±5.78a
Diet 2
9.4±2.31b
30.0±3.87b
29.8±2.43c
58.0±4.32b
Diet 3
12.5±2.15a 38.0±4.12a 48.2±2.18a 59.6±3.89b
Diet 4
14.0±3.14a
43.0±34a 43.6±3.11ab 75.4±4.13ab
Diet 5
9.0±2.17b 27.0±1.78bc 13.6±1.11d 98.6±5.09a
Diet 6
6.6±1.68c 20.0±1.58c
36.0±3.54b
60.4±2.91b
Diet 7
12.5±2.34a 38.0±3.45a 14.2±2.16d
109.9±6.43a

The processing of cocoyam tubers resulted in a significant improvement over the raw in most
of the measurement recorded as shown in Table 2. Fish fed with boiled cocoyam (BC) diet gained
significantly (P < 0.05) higher weight than those fed RC diet. The improved weight gain of the fish fed
BC may be associated with the beneficial effect of boiling which resulted into better nutritional value
and digestibility. (Abdurashid Agumnobi 2009). The improved digestibility could be as a result of the
inactivation of the anti-nutritional factors, which interferes with the digestive process (Ghazi et al.,
2002). The decreased weight gain observed in fish fed with RC both at 25 and 50% inclusion levels
suggest that nutrients in the RC were not as available or probably abundant as in the BC diets. Tannins
and trypsin inhibitors have been reported to affect nutrient availability and utilization by monogastric
animals (Kocher et al., 2002). Therefore, the poor body weight of the fish could be due to the poor
digestibility and absorption of nutrients in raw cocoyam diets when compared to the processed
cocoyam meal. Better growth performance and nutrient utilization was recorded for the control diet,
this is similar to the findings of Omoregie et al (2009) when they fed graded levels of sweet potatoes
peel in comparism to maize to Cichlid. There was no significant difference (P > 0.05) in feed intake

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Processed Cocoyam Tuber as Carbohydrate Source in the Diet of Juvenile
African Catfish (Clarias Gariepinus) 458

among all treatments; one of the most common difficulties observed when alternative sources of
feedstuffs are used in fish diets is acceptance and palatability by the fish (Domingues et al 2003).
However, in this present study, the fish avidly consumed the experimental diets.
The result of the feed conversion ratio of Clarias fed RC, BC, FC and CWC diets showed that
the FCR of fish fed BC and the CWC (control without cocoyam) diets were significantly (P < 0.05)
superior to those fed 25% RC (raw cocoyam) and those fed 50% FC (fermented cocoyam) diets. This
could be attributed to the improvement in the availability and utilization of nutrients in this particular
diet that was boiled. The poor FCR of the fish fed 25% and 50% raw cocoyam inclusion may not be
unconnected with the effect of age on the response to residual tannins and trypsin-inhibitor, which
could be beyond the tolerable limit of the young Clarias juvenile fish.Poor FCR, PER and SGR were
also recorded at higher inclusion level by Ofojekwu et al 2003 and Omoregie et al (2009). Fish fed
CWC diets showed better protein efficiency ratio than those fed raw, boiled and fermented diets. This
could probably have resulted in the improved weight gain of fish on the control diet.
Economic indices showed decreased in price of feed with the inclusion of cocoyam
meal,especially at higher inclusion level of the test ingredient,this may be attributed to the higher cost
of maize brought about by the keen competition for maize between man and other livestock
(Arinjeniwa et al 2000).Despite the above stated point,the economic index was lowest on control diet
as a result of the outstanding result obtained from the growth and nutrient utilization parameters.Cost
of processing varies among the diets although this may not be significantly different.
Blood is a good indicator in determining the health of an organism (Joshi et al., 2002c), it also
acts as a pathological indicator of the whole body, and hence hematological parameters are important
in diagnosing the functional status of an exposed animal to suspected toxicant (Omitoyin 2006).
Haematological characteristics of most fish have been studied with the aim of establishing normal
value range and any deviation from it may indicate a disturbance in the physiological process (Rainza-
paiva et al., 2000). The values obtained in this experiment for both the PCV and Hb (control diet) were
within the normal ranges (37.0±2.18 and10.10±0.214 respectively ) recommended for Clarias
gariepinus (Sunmonu 2008 and Adedeji 2009). Since most of the heamatological values obtained in
this study at 50% inclusion level fall significantly below that of the control, it could be suggested that
the diets tested had major physiological stress on the health status of the fish studied. Previous
haematological studies of nutritional effects brought knowledge that erythrocytes, PCV and Hb are
major and reliable indicators of various sources of stress (Rainza-Paiva et al, 2000) and these
parameters decreases in the present of antinutritional factors (Osuigwe et al 2007).Reduction in PCV
and Hb value at high substitution rate and between control and raw test ingredient was also observed
by Osuigwe et al (2007) when they fed different dietary level of raw and boiled jack bean to juvenile
Heterobranchus longifilis. This result is in agreement with earlier reports that heat treatments reduced
the level of anti-nutritional factors in jackbean seed (Udedibie and Carlini 1998).Values obtained for
both the total lipid protein and cholesterol (55.8mg/l and 85.1mg/dl respectively) are within the range
stated by Omitoyin et al 2005 (56.8 g/l) and 57.0g/l stated by Fagbenro et al (2000)for Heterotis
niloticus..Reduction in plasma protein as a result of handling stress was observed by Gbore et al (2006)
following the same experience obtained in this study as higher inclusion level of cocoyam in test diets.

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459
Aderolu, Ademola Zaid, Lawal Muyideen Owonire and Oladipupo, Muinat Oluwakemi
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