China
Africa
Explore chapters and articles related to this topic
Fry and Fingerling Production
Published in Hillary S. Egna, Claude E. Boyd, Dynamics of POND Aquaculture, 2017
Bartholomew W. Green, Karen L. Veverica, Martin S. Fitzpatrick
Fish exposure to androgens usually occurs through dietary treatment. The most commonly used androgen is 17 α-methyltestosterone (MT). Feed preparation has been described in detail by Popma and Green (1990). Feeds that contain 25 to 45% protein are recommended, although a 20% protein feed has been used successfully (Popma and Green, 1990). Androgen-treated feed is prepared by (1) thoroughly mixing androgen that has been dissolved in solvent (usually 80 to 95% ethanol) with finely ground (approximately 0.5- to 1.0-mm diameter particle size) feed or (2) spraying the dissolved androgen and solvent onto the feed. The advantage of the first method is the minimal atomization of androgen solution, which reduces the chance for contamination of workers or workplace; the second method is advantageous in that the volume of solvent can be reduced. In both cases, the alcohol is allowed to evaporate and the dried feed stored in a cool, well- ventilated area or refrigerated until used; good air circulation around the complete feed container helps maintain feed quality during storage. Because MT is photosensitive, pure MT should be protected from sunlight, and treated feed should not be dried or stored exposed to direct sunlight. Feed prepared with MT that has been stored exposed to light and air, and MT-treated feed stored exposed to light and air were ineffective in sex inversion of O. mossambicus (Varadaraj et al., 1994). Otherwise, MT is quite stable within conditions normally encountered on fish farms. Refrigeration, however, is recommended for treated feed to ensure feed quality. It is not necessary to use reagent or USP grade ethanol as a solvent for MT. In fact, in Honduras denatured ethanol (denatured with glycerin at 0.5% by volume) is obtained from a local distillery at low cost and used successfully.
Ecological risk of 17α-methyltestosterone contaminated water discharged from a full water recirculating earthen masculinization pond
Published in Human and Ecological Risk Assessment: An International Journal, 2021
Sudtida Pliankarom Thanasupsin, Lita Chheang, Chim Math
17α-methyltestosterone (MT) is a synthetic and anabolic steroid hormone. It has a close chemical structure with testosterone, the naturally produced androgenic hormone. In aquafarming, culturing all-male tilapia has several economic benefits such as achieving a higher growth rate, minimizing energy losses associated with gonadal development and reproduction, and achieving uniformity in size at harvest (Júnior et al. 2012; Mlalila et al. 2015). Examples of hormones, that can be used to induce an all-male population of Nile tilapia, are 19-norethyltestosterone, fluoxymesterone, ethyltestosterone, 17α-methyltestosterone (MT), mesterolone, androstenedione, trenbolone acetate (TBA), testosterone, 17α-ethynyltestosterone, dihydrotestosterone, and 17αmethyldihydrotestosterone (Golan and Levavi-Sivan 2014; Homklin et al. 2011; Mlalila et al. 2015; Ong, Chotisukarn, Limpiyakorn 2012; Passantino 2012). Although immersion of newly hatched tilapia fry in an aqueous 17α-methyldihydrotestosterone and trenbolone acetate can be used for masculinization of tilapia (Oreochromis niloticus), the yields of sex reversal percentage are relatively low (Contreras-Sanchez et al. 1997). Tilapia and other Oreochromis species are mouthbrooders. The female broodfish carry the fertilized eggs in their mouth. Treatment with MT should begin once the yolks disappeared or after the 15th day post-fertilization (Contreras-Sanchez et al. 1997; Ong et al. 2012). In Thailand, the most common sex-reversal treatment to induce all-male populations of tilapia involves feeding sexually undifferentiated fry four to five times a day with MT-impregnated food containing 30–60 mg MT/kg of diet (Adnan and Thanasupsin 2016; Basavaraja and Raghavendra 2017; Contreras-Sanchez et al. 1997; Ferdous and Ali 2012; Fitzpatrick et al. 1999; Kuwaye et al. 1993; Kwon et al. 2000; Marjani et al. 2009; Pradeep et al. 2012; Rahma et al. 2015; Straus et al. 2013). During the hatching step, maintaining the dissolved oxygen level in the hatching tray is one of the crucial parameters for the fry to survive. In a close system, farmers generally use internal water as a source for the intensive water circulation in the hatching tray. Later, the fry is transferred to grow in the stews (nylon fish pot nets or net cages) located in the earthen pond.