1. Use of fresh bull and hog testis in sex reversal of Nile tilapia fry
Daniel Meyer, Marco Guevara
Willie Chan and Claudio Castillo

2. 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 and by participating institutions.

3. Introduction 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

4. Objective
Evaluate the use of fresh bull and hog testis in the sex reversal of Nile tilapia Oreochromis niloticus fry

5. Location:
Aquaculture Station at the Escuela Agrícola Panamericana, Honduras

6. Fish Fertile eggs collected from incubating females
Artificial incubation

7. Fish 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

8. Preparation of meat products
fresh testis cut and processed with grinder
salt added
dried at 32° C
stored frozen
purchased meat meal from local supplier

9. Water quality Dissolved oxygen and water temp a.m. and p.m.
Experimental units cleaned with syphon every other day

10. Sex determination thru microscopy
Fry grown to a total length ± 50 mm
Gonads removed and observed 50X

11. Sex determination via microscopy

12. Male fry = No presence of oocytes, granular texture of the gonad
Fuente Popma and Green

13. Female fry = oocytes observed at varios stages of development
Fuente Popma and Green

14. Experimental design: Three treatments: Four repetitions of each
bull testis
hog testis
meat meal
Four repetitions of each
Chi2 for evaluating treatment effectiveness
ANOVA with survival results
Statistical Analysis System (SAS® 2003)

15. Results and discussion

16. Water quality: dissolved oxygen2 4 6 8 10 12 20 30 40 50 60 70 80
Días
mg/L
H. Carne
T. Toro
T. Verraco
Wet lab
Greenhouse
Figure 1. Average daily dissolved oxygen concentration, Zamorano, Honduras. Water in all containers was aerated continuously.

17. Water quality: temperature5 10 15 20 25 30 35 40 50 60 70 80
Días
Degrees C
Meat meal
Bull testis
Hog testis
Wet lab
Greenhouse
Wet lab
Figure 2. Average daily water temperature for 20 L buckets and net enclosures during a 71-day feeding trial, Zamorano, Honduras.

18. No electricity on night of day 20!50
100
150
200
250 10 20 30 40 60 70 80
Days
Number of fry
Meat meal
Bull testis
Hog testis
No electricity on night of day 20!
Figure 3. Number of fry surviving based on original 200 fish for each treatment.

19. Fry survival by environment
Culture environment
Culture
days
Initial population
Final population %
survival
Wet lab
(20 L buckets)
1 thru 36
600
241
40.2%
Greenhouse
(net enclosures)
36 thru 71
219
90.9%
Overall fry survival for 71-day long experiment was 36.5%.

20. Fry survival by environment
Low DO detected after electrical black-out (on day 20 of experiment)
100% meat based feeding regime (tilapia is primarily an herbivore)
Small initial size of fish (mortality observed 20 days after stocking)
Low survival rates reported in previous studies
Haylor, G. S.; A. B. Pascual 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:
Phelps, R.P Sex Reversal: the directed control of gonodal development un tilapia, pages En D.E.Meyer (editor). Memoria 6to simposio Centroamericano de Acuacultura. Asociación Nacional de Acuicultores de Honduras y PD/A CRSP, Honduras.

21. Fry survival by treatment
Initial number fry/repetition
Final number
fry/repetition %
fry survival
Meat meal 50 24
48a
Bull testis 16
32b
Hog testis 15
30b
Unable to explain observed difference in survival by treatment!

22. Growth of the fry during 71 days
Average
body weight (g)
body length (cm)
Treatment
Initial
Final
Meat meal
0.01
3.48 ± 0.60
0.8
4.8 ± 0.5
Bull testis
4.13 ± 0.48
5.7 ± 0.3
Hog testis
3.88 ± 0.16
5.5 ± 0.2

23. Percent of male fish Treatment % male fish Meat meal 58 ± 4.9
Bull testis
87 ± 5.6
Hog testis
83 ± 7.7

24. 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.

25. 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%!

26. Recomendations
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