| Author | Nguyen Van Bang |
| Call Number | AIT Thesis no. AS-99-02 |
| Subject(s) | Nile tilapia
|
| Note | A thesis submitted in partial fulfillment of the requirements
for the degree of Master of Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. AS-99-02 |
| Abstract | Feminization is a standard technique used in the development and application of the
important YY male technology for mass production of monosex tilapia. Feminization
techniques currently use the estrogen Diethylstilbestrol (DES), a toxic hormone with several
disadvantages. There is a need to further optimize feminization protocols and ideally to look
for an alternative, less toxic estrogen. Furthermore, recent studies have shown that constantly
elevated temperatures can influence both sex differentiation and efficiency of sex reversal. It
is thus of importance to determine whether extreme fluctuations in ambient temperatures that
occur in different environments, can also effect sex ratio.
This study had two experimental components. The first set out to determine the effect
of high temperature on feminizing efficiency of Diethylstilbestrol (DES) and Ethynylestradiol
(EE) in 0. niloticus using oral application of treated feed with two modes of administration,
loose powdered feed or feed bound in an agar or gelatin gel. Hormone at dose of 0 (control) or
100mg.kg"1 was administrated in feed in loose form and hormone treated food was also
applied bound in agar or gelatin. Sexually undifferentiated fry were reared in small cages
installed in aquaria set up under ambient and high (36°C) temperature regimes for 25 days.
The fry were then grown-on in hapas in pond for sexing. The results showed that feminizing
efficiency of EE were better than that of DES at ambient temperature. High temperature
increased efficiency of both hormones although this effect was greater for DES. The gel bound
mode of administration did not affect treatment efficiency and was more labor intensive but
utilized smaller amounts of hormone but. Using agar or gelatin gel could save significantly on
the amount of hormone used but does not have major benefits.
The second experiment set out to determine the effect of ambient temperature
fluctuations on sex determination in 0. niloticus and feminizing efficiency of DES hormone at
dose of 1 OOmg.kg·1 in loose feed form. Sexually undifferentiated fry were reared in four in
environments (shallow hapa, deep hapa, outdoor tank and indoor tank), in which different
temperature fluctuation regimes were desired, with fluctuations likely to be greatest and with
the highest extremes in shallow hapas and outdoor tanks. Result showed a significant
difference in proportion of females in untreated fish between but not within hapas and tanks
indicating that the temperature fluctuations, which had been much lower than anticipated, did
not effect sex ratio. There was no effect of environment on the efficiency of the DES
treatment.
Using of EE at ambient temperature can be recommended as an alternative for DES
treatments. Evidence for an effect of holding environment on sex determination was an
important finding and the type of environment in which fish are held should always is
considered when evaluating work on sex determination and differentiation in tilapia. |
| Year | 1999 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. AS-99-02 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural and Aquatic Systems (AS) |
| Chairperson(s) | Mair, Graham C.; |
| Examination Committee(s) | Bart, Amit;Yakuppitiyage, A.; |
| Scholarship Donor(s) | Government of Japan; |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 1999 |