Three groups of Sarotherodon niloticus fry were fed for 8 weeks on diets either treated with 17- & methyltestosterone (MT), alcohol (CA), or untreated (CO). Growth rate and food utilization in the different groups were compared. Results indicate that the best growth, Feed Conversion Ratio (FCR), Protein Efficiency Ratio (PER) and Mean Growth Rate (MGR) were obtained with the MT diet. There was no significant difference (P 0.05) in growth and food utilization of the CA and CO fry, nor in the mortality rate of the 3 treatments. The androgen, methyltestosterone promotes growth and protein anabolism without producing toxic effects in S. niloticu

Madu, C.T.

Ufodike, E.B.C.

English

Aquatic Commons

1LiraNA57 TNTESTIGATIOU Li.410 THE EFIT'ECTS OF
, pE-1:1 rfcrrfftstÉ,'Mit',--ON
GROTITTi 1F,7 -3arocflerodon (L) Fr. - .
-
by
E.B.C. Ufodike & C.T. Madu
Fisheries and Hydrobiology Research Unit
Department of Zoology
University of Jos Plateau State
Nigeria
ABSTRACT
Three groups of Sarotherodon niloticus fry were fed for/8 weeks on diets either
treated with 17- & methyltestosterone (MT),- alcohol (CA), or untreated (CO).
Growth rate and food utilization in the different groups were compared. Results
indicate that the best growth, Feed Conversion Ratio (FCR), Protein Efficiency
Ratio (PER) and Mean Growth Rate (MUR) were obtained with the MT diet. There was
no significant difference (P 0.05) in'growth and food utilization of the CA and
CO fry, nor in the mortality rate of the three treatments.The androgen, methyltes-
tosterone promotes Erowth gnd protein,anabolism without producing toxic effects in
S. niloticus.
INTRODUCTION
One of the major set-backs in the intensive culture of Sarotherodon niloticus and
other tilapia species is their prolific fecundity (Lowe, 1955; Hickling, 1960).
This leads to over-population of ponds and high competition, and hence production
of tiny fish. To overcome this, procedures such as combined stocking with pisci-
vorous fishes, irradiation, monosex culture, cage culture, gynogenesis and sex
reversal have been tried. Of all the methods researched into, sex reversal
involving the use of either an androgen o r estrogen seems to be the most modern
and the,most acceptable (Yamamoto, 1953; Guerrero, 1975; Fontaine, 1976; Tayamen
& Shelton, 1978; Balarin, 1979; Nagy et al., 1981; Donaldson & Hunter, 1982).
However, Yashouv and Eckstein (1965) found that a female hormone like ethynyles-
tradiol caused high mortalities and growth retardation in fish. Guerrero (1975)
using S. aurea observed that androgen treated fish had a better growth than
estrogen treated fish or the untreated fish. He suggested that this was due to
the hormonal effect on metabolism. Using other species of tilapia or sarotherodon,
similar results have been obtained by other workers (Dadxie, 1974; Tayamen &
Shelton, 1978). Odunze, (1981) obtained 100% sex-reversal efficiency with either
60mg of ethynyltestosterone/kg of feed or 30mg of methyltestosterone/kg of feed
in S. niloticus.
It is striking that there is no available literature on the,-influence of sex
reversal hormones on food utilization in S.niloticus. Work by Shackley and King
(1978) in which they observed that high molecular weight protein was transfered
from the liver to the ovary and accumulated in developing oocytes in Blennius pholis
(L) suggests that protein efficiency ratio in fish could be greatly affected by
hormone treatment.
It would therefore be useful to determine the.effect_of,methyltestosterone on food
conversion and growth of S.niloticus fry. This knowledge would be useful in
deciding whether this hormone could be used on long term basis to "fatten"
S. niloticus. Such an exercise would of course depend nöt only on the economy,
but also on the fish tissue residue of the androgen on withdrawal of hormonal
treatment.
MATERIALS & METHODS
Commercial pelleted fish feed from Nigerian Institute for Oceanography and Marine
Research (NIOMAR), Lagos, was crushed and sieved through a 0.5 mm mesh-size sieve.
The hormone, 17-&- methyltestosterone (Sigma Chemical Co. Ltd., USA) was dissolVed
in 95% solution of alcohol and mixed with diet at-30mg hormone/kg diet. Homogenisa-
tion was accomplished with a food mixing machine. Two control diets, one treated
with only alcohol (CA), the other treated with neither alcohol nor hormone (CO)
were similarly prepared. All diets were dried over 'a fan heater in a drying
72
cabinet at 30°C.
Approximately 1000 fry of Sarotherodon niloticus collected from Panyam Fish
Farm near Jos were used for this investigation. Fish measured between 9-12 mm
and weighed 68.83 mg + 2.08 mg at the start of the experiment. During quarantine
treament whith lasterl one week, fish were fed 3 times daily on a total of 3% of
ther_r body meight on the NIOMAR diet. On the first and fourth days of
guar mtine 'period, fish were dipped for 10 seconds in 1ppm solution of potassium
perninganate. Fish were weighed and stocked at 60 fry/tank in 12 green plastic
tank3 held in a water recycling system of Jos University Applied Hydrobiology and
Fis1Hries Aquaculture Unit (Madu, 1982), care being taken to balance out the
weights of fish in the tanks. Each tank contained 16 litres of water and flow-
throlIgh rate was 2L/minute. The water temperapre was same as that of the Aqua-
culture lab which was maintained constant at 25 C + 1.0°C with a thermostatic air-
condAioning unit. Each diet was fed to fry in a et'of 4 tanks, thus providing
4 replicates per treatment. Each tank received 10% body weight of fish daily at
8 am, 12 noon, 4 p.m and 8 p.m, a little at a time till fish picked up all the
feed, All fry in each tank were weighed weekly, and weight fed was adjusted in
the Iight of the new weight of fish in each tank. During weighing, fry in each
tank were netted, quickly dried on soft filter paper and weighed in water con-
tained in a small plastic beaker on a top loader metterler balance with an
accuracy of + 0.1mg. Using this value and the number of fish per tank, the mean
weight of eaTh fish per tank was computed. Mean weight of fish per treatment was
then worked out and used in plotting the growth curve. At the end of the 8 week
experiment, 10 fry per tank were netted, killed in a solution containing 0.5g
benzocaine (predissolved in alcohol) in 2L water and then separated randomly into
2 sections, each containing 5 p.sh. Each group of 5 fish were then analysed for
moisture by oven-drying at 105 C for 48 hours, Kjeldahl protein, proximate fat
composition by the either extraction method using soxhlet epparatus and ash as
detailed in AOAC methods (AOAC, 1980). The commercial diet was similarly analysed.
Data Analyses
The IY!ean Growth Rate (MGR). was computed after the method of Wayne and Davis (1977).
Food Conversion Ratio (FCR) Was worked out suing the formula:
Weight of food consumed per week (g)
Weight gained by fish per week (g)
Protein Efficiency Ratio (PER) was also computed after the method of Osborne, et.al
(1919). This is the efficiency with which fish utilise dietary 'protein. Analyses
of va-iance (ANOVA) was done using Duncans multiple range 0 test (Duncan, 1955).
Table 1:- Proximate of commercial diet and fry (% weight»composition carcass
73
For fish composition, figures in the same row having the sane superscript .are not
significantly different (P::>0.05).
1Nitrogen Free Extract; computed as difference between subtotals and 100.
Components Diet FISH
+ SEM
Initial M T C A C 0 (for.fish)
Moisture 8.9 -15.00a 77.00a 79.50a 8020a 4.51
Crude Protein 47.5 9.20a 6.001- 12.50a 12.00a 1.22
Crude Fat 18.5 0.69a 1.50 1.00a 0.90a 0.42
Ash 9.6 1.50a 1.00a 1.30a 1.25a 0.27
Sub-totals 84.5 96.39 95.50 94.30 94.35
N F Ei 15.5 3:61 4.50 5.70 5.65,
RESULTS & DISCUSSION
The best growth (Fig. 1) was recorded in fry on M T diet. There waa no signi-
ficant difference (P:>0.05) in growth of the C A-and C 0 fry. There was no
significant difference- (P >0.05) in the moisture, crude fat and ash contents of
the M T fry was significantly higher (P>0.05) than the rest (Table 1). The food
conversion Ratio -(F C R) with the M T was 0.403 and was approXimately 0.30 with
the C A and C O. diets (Table 2). The resulta obtained for the Protein Efficiency
Ratio (P E R) and Mean Growth Rate (M,G R) follow the sane pattern as those for
F C R, with no significant difference (P>0.05) occuring between the values
obtained with the C.A and C 0 diets, and values obtained with the M T diet were
significantly better (N:=0,05). No particular diet produced significantly higher
mortality (P>0:05). -Rather, tOrtality in .each group during the 8 weeks experi-
mental period was approXiMately-28%L(Tablè '2)'.and muat have been due to stress
during weighing.
From the results obtained, it would appear that the indOrporation of tne androgen
methyltestosterone in the diets of the fish enhanced protein anabolism, and groWth.
Similar growth patterns were earlier observed by Guerrero (1975)\in Tilapia áLlE22,
Tayamen and Shelton (1978) in Sarotherodon niloticus and Donaldson and Hunter-(-1982)
in rainbow troUt. The M G R obtained in this work was lower than values obtained. .
by Tayamen and Shelton (1978). This could be due to differences in both quality
and quantity of feed. Tayamen and Shelton's diets and fish were however not
analysed. Results obtained for F C R and P E R indicate that the M T fry met-
abolised their food better than the C A and C 0 fry. It is not likely that this
could have been at such an early stage, due to differences in growth rates of males
and females. The anabolic effect of the androgen must have been an over-riding
factor. The similarity or results obtaihed with the C A and C 0 diets confirm
that the use of alcohol as a solvent for the androgen did not affect the quality of
the dial,. It is also confirmed that unlike some estrogena (Yashouv & Eckstein,
1965) androgen treatment or the use of alcohol for its desolution does not lead
to mortalities in the fry of S. niloticus. However, since there could be some
danger to the consumer of fish "fattened" with androgens a long-term study of the
effects of this hormones on,tissue metabolism'of fish is necessary. This should
invelve monitoring residues of'androgen in fish tissue after treatment. Cost-
benefit ratio-should also be considered before this hormone can be used for increas-
ing thé size of harvestable S. niloticus, whose tiny size at maturity Often renders
it a thrash fish.
Tqble 2:- Food utilization and mortality rate of
methyltestosterone treated and untreated fish
Figures in the sane row having the sane superscripts are not significantly
different (P >0.05).
1In mg/g/day.
REFERENCES
Association of Official Analytical Chemists (AOAC) (1980) Official Metho0 of
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Balarin J.D. (1979) Tilapia - A gx.dde tò their biolo and culture in Africa.
Univ. of Stirling Press, Scotlandi' -5q,65 Pp.
Dadzie S (1974) A preliminarvriport on the use of metaliibure.in tilapia
culture. African Tropical Hydrobiology & Fisheries, 4: 127-141
74
M T CA
TREATMENTS
CO E M
F C R 0,403 0.290 0.298 0.030
P E R 2.52b
199a
0.116
M G R1 30.28b 27.71a 28.13a 0,734
% Mortality 28.00a 28.25a 28.00a 0.166
Donaldson E.M. & Hunter G.A...(1982) Sex control in fish with particular
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Duncan D.B. (1955) Multiple range and multiple F-test. Biometrics 11: 1-42
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the growth promoting value of proteins J. Biol. Chem. 37: 223-224
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Juournal of Fish Biology 13:179-193
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A preliminary investigation into the effects of a sex-reversal androgen, methyltestosterone, on food utilization and growth of Sarotherodon niloticus (L) fry

A preliminary investigation into the effects of a sex-reversal androgen, methyltestosterone, on food utilization and growth of Sarotherodon niloticus (L) fry

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