Untitled

Abstract

Production of YY-males is one of the most important alternatives to the commercial use of hormones for producing monosex populations in the culture of Nile tilapia. One of the final stages of YY-technology is the feminization of the progeny of XY-females in order to obtain YY-females, which when crossed with YY-males makes possible to obtain populations composed of 100% YY-males. The aim of the study was to evaluate the effects of four concentrations (100, 200, 300, 400 mg kg -1 ) of estrogen 17α-ethinylestradiol (EE 2 ) on the sex ratio, growth, condition factor (CV) and gonadosomatic index (GSI) of the progeny of XY-females. Significant differences were observed in wet weight, total length and CV during the experiment; however, final values in EE 2 -treated groups showed not significant differences with control group. The observed proportion of females deviated significantly from the proportion of females expected in the progeny of XY-females in all groups fed EE 2 ; however, only 90% feminization was attained. The group fed 200 mg kg -1 of EE 2 showed a significantly higher value of GSI in comparison to that observed in the control group. By increasing the concentration of EE 2 it is possible to increase the proportion of females without affecting growth or GSI.

EFFECTS OF THE USE OF 17Î"™-ESTRADIOL FOR <i>Leporinus macrocephalus</i> FEMINIZATION

“…Thus, it is possible that diets supplemented with E 2 increase the circulating levels of this hormone in the treated fish, promoting the gonadal differentiation during the initial development of this species. In fact, this has been seen in several studies (Marín-Ramírez et al, 2016;Juárez-Juárez et al, 2017;Alcántar-Vázquez, 2018;Vidal-López et al, 2019) in which diets supplemented with E 2 promote fish gonadal differentiation.…”

“…It has been previously shown that the sexual differentiation in fish is regulated by sex steroid hormones (Singh, 2013;Pradhan and Olsson, 2015;Hoga et al, 2018) and indirectly by steroidogenic enzymes (Baroiller and D'Cotta, 2001;Tokarz et al, 2015;Di Rosa et al, 2016;Koyama et al, 2019). However, environmental factors (Hunter and Donaldson, 1983;Devlin and Nagahama, 2002;Piferrer et al, 2012;Díaz and Piferrer, 2015) and hormonal manipulations may intensify this process (Piferrer, 2001;Lin et al, 2012;Alcántar-Vázquez et al, 2015;Marín-Ramírez et al, 2016;Juárez-Juárez et al, 2017). In this concern, the most conventional route of ovarian development involves the transcription of the Cyp 19a1a gene and the production of the enzyme aromatase complex (P450arom).…”

Effect of Fluoxymesterone on Sex Proportion and Growth Performance of Nile Tilapia (Oreochromis niloticus L.).

“…Although the duration of hormonal treatment has been pointed out as an important factor to successfully induce high rates of sex reversal, in recent years, both feminization and masculinization experiments with Nile tilapia, have shown that it is not necessary to administer the hormone for more than 20 days after the onset of the labile period to induce high rates of sex reversal [12,42,43,44]. Nakamura and coauthors [45] reports that under the light microscope, the first signs of gonadal sex differentiation appear in Nile tilapia fry at 23-26 days after hatching with the formation of the ovarian cavity in the XX gonad or the efferent duct in the XY gonad.…”

“…Vol.66: e23210792, 2023 www.scielo.br/babt in a general way, of the health status of the reared fish [58,59,60]. Values close to 2.0 have been reported for the Nile tilapia and its hybrids grown under optimal [12,54,59,60]. The CF can also be implemented to assess the physiological state of fish under potential stress [55], such as feeding Nile tilapia fry with a steroid enriched food.…”

“…Therefore, for many years the production of monosex, all-male populations, has been recognized as the most effective technique to increase Nile tilapia production under commercial culture conditions [3,7,8,9]. Several approaches have been developed to achieve all-male populations, the most commonly applied in the industry today being direct hormonal sex-reversal by feeding fry with different steroids [3,10,11,12].…”