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Use of fresh bull and hog testis in sex reversal of Nile tilapia fry

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.

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Use of fresh bull and hog testis in sex reversal of Nile tilapia fry

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  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 theAquaculture 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.

  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: 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 oxygen Wet lab Greenhouse 12 10 8 mg/L 6 4 H. Carne T. Toro 2 T. Verraco 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.

  17. Wet lab Greenhouse 35 30 25 20 Degrees C 15 Meat meal 10 Bull testis Hog testis 5 0 0 10 20 30 40 50 60 70 80 Días Water quality: temperature Wet lab Figure 2. Average daily water temperature for 20 L buckets and net enclosures during a 71-day feeding trial, Zamorano, Honduras.

  18. 250 200 150 Number of fry 100 Meat meal 50 Bull testis Hog testis 0 0 10 20 30 40 50 60 70 80 Days 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 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. 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.

  21. Fry survival by treatment Unable to explain observed difference in survival by treatment!

  22. Growth of the fry during 71 days

  23. Percent of male fish

  24. Chemical analysis of testis 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

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