Transcript Slide 1

Use of fresh bull and hog testis in
sex reversal of Nile tilapia fry
Daniel Meyer, Marco Guevara
Willie Chan and Claudio Castillo
Funding for this research was provided by the
Aquaculture
Collaborative Research
Support Program
The Aquaculture CRSP is funded in part by United States Agency for International
Development (USAID) Grant No. LAG-G-00-96-90015-00 and by participating institutions.
Introduction
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Modern techniques for culturing tilapia
MT is synthetic product
Increasing demand for organic foods
Little published work on use of natrual
sources of testosterone in sex reversal
Objective
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Evaluate the use of fresh bull and hog
testis in the sex reversal of Nile tilapia
Oreochromis niloticus fry
Location:
Aquaculture Station at the Escuela Agrícola Panamericana, Honduras
Fish
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Fertile eggs collected from incubating females
Artificial incubation
Fish
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Fry (± 8 mm) were treated in 20 L plastic buckets in lab
Continuous aeration, daily cleaning and water exchange
After 36 days fry transferred to cylindrical net enclosures (3
mm mesh) located in a greenhouse for ongrowing to > 50
mm
Preparation of meat products
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fresh testis cut and processed with grinder
salt added
dried at 32° C
stored frozen
purchased meat meal from local supplier
Water quality
Dissolved oxygen and water temp a.m.
and p.m.
 Experimental units cleaned with syphon
every other day
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Sex determination thru microscopy
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Fry grown to a total length ± 50 mm
Gonads removed and observed 50X
Sex determination via microscopy
Male fry = No presence of oocytes, granular texture of the gonad
Fuente Popma and Green
Female fry = oocytes observed at varios stages of development
Fuente Popma and Green
Experimental design:
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Three treatments:
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bull testis
hog testis
meat meal
Four repetitions of each
Chi2 for evaluating treatment effectiveness
ANOVA with survival results
Statistical Analysis System (SAS® 2003)
Results and discussion
Water quality: dissolved oxygen
Wet lab
Greenhouse
12
10
8
mg/L
6
4
H. Carne
T. Toro
T. Verraco
2
0
0
10
20
30
40
50
60
70
80
Días
Figure 1. Average daily dissolved oxygen concentration, Zamorano,
Honduras. Water in all containers was aerated continuously.
Water quality: temperature
Greenhouse
Wet lab
Wet lab
35
30
Degrees C
25
20
15
Meat meal
Bull testis
Hog testis
10
5
0
0
10
20
30
40
50
60
70
80
Días
Figure 2. Average daily water temperature for 20 L buckets and net
enclosures during a 71-day feeding trial, Zamorano, Honduras.
No electricity on night of
day 20!
250
Number of fry
200
150
100
Meat meal
50
Bull testis
Hog testis
0
0
10
20
30
40
50
60
70
Days
Figure 3. Number of fry surviving based on original 200 fish
for each treatment.
80
Fry survival by environment
Culture
environment
Culture
days
Initial
population
Final
population
%
survival
Wet lab
1 thru 36
600
241
40.2%
36 thru 71
241
219
90.9%
(20 L buckets)
Greenhouse
(net enclosures)
Overall fry survival for 71-day long experiment was 36.5%.
Fry survival by environment
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Low DO detected after electrical black-out
(on day 20 of experiment)
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100% meat based feeding regime (tilapia is
primarily an herbivore)
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Small initial size of fish (mortality observed 20 days
after stocking)
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Low survival rates reported in previous
studies
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Haylor, G. S.; A. B. Pascual. 1991. Effect of using ram testis in a fry diet for Oreochromis niloticus (L.) on
growth, survival and resultant phenotypic sex ratio. Aquaculture and Fisheries Management 22: 265-268.
Phelps, R.P. 2001. Sex Reversal: the directed control of gonodal development un tilapia, pages 35-60. En
D.E.Meyer (editor). Memoria 6to simposio Centroamericano de Acuacultura. Asociación Nacional de
Acuicultores de Honduras y PD/A CRSP, Honduras.
Fry survival by treatment
Initial number
fry/repetition
Final number
fry/repetition
%
fry survival
Meat meal
50
24
48a
Bull testis
50
16
32b
Hog testis
50
15
30b
Treatment
Unable to explain observed difference in survival by treatment!
Growth of the fry during 71 days
Average
body weight (g)
Average
body length (cm)
Treatment
Initial
Final
Initial
Final
Meat meal
0.01
3.48 ± 0.60
0.8
4.8 ± 0.5
Bull testis
0.01
4.13 ± 0.48
0.8
5.7 ± 0.3
Hog testis
0.01
3.88 ± 0.16
0.8
5.5 ± 0.2
Percent of male fish
Treatment
% male
fish
Meat meal
58 ± 4.9
Bull testis
87 ± 5.6
Hog testis
83 ± 7.7
Chemical analysis of testis
Processed meat
product
Testosterone
level
Fresh ground bull testis
18.8 ppm
Fresh ground hog testis
20.4 ppm
Testosterone levels in dried testis would be > 60 ppm.
Conclusions
Bull and hog testis were effective to
produce mostly male fry of tilapia
beginning sex reversal at a small total
body length (± 8 mm)
 Low survival of fry attributed to water
quality problems and possible nutritional
deficiency.
 In green water survial of fry was > 90%!
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Recomendations
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Attempt to use testis for sex reversal in outdoor
tanks with green water.
Use freeze-drying of testis for better preparation
and stroage
Develop a methodology for extracting hormone
from fresh testis
Fin