Appel, H.B., Leboute, E.M.
Abstract:
The excessive and precocious reproductive capacity of Nile tilapia is harmful for its commercial production in growout ponds. The present study aimed to obtain sex reversal to male of Nile tilapia fry submitted to 2 h immersion bath in androgens solution. The treatments were applied on 7th or 14th day after hatching, using 17-micro-methyl-testosterone (MT) and androstenedione (AND) androgens, at 200 and 400 microgram/l dosage. The experiment was performed in 126 days. It was used the complete randomized Design with 3 replicates per treatment. The experimental unit was constituted of 50 animals kept in 100 liter White plastic tank. The sex was identified by examination of genital papilla confirmed through gonadal macroscopis exam. The administration of AND to 7 days old fry resulted masculinization (P<0.05) on 200 microgram/l (64.28% of male) and 400 microgram/l (62.74% of male) dosage, while MT in the same dosage and age wasn't effective (P>0.05). Hormone administration on 14th day of 400 microgram/l dosage resulted in 70.19% and 72.34% of male (P<0.01) with the AND and MT, respectively. AND administration at 200 microgram/l dose on the 14th day caused (P<0.01) feminilization (61.77% female) and sterile animals. There weren't treatment effects about weight gain (P>0.05), and the results about mortality rate were incongruous.
This study was funded by CAPES and CNPQ (Brazil).
(Campo Experimental de Piscicultura de Camboriu, Estacao Experimental de Itajai, Empresa de Pesquisa Agropecuaria e de Extensao Rural de Santa Catarina, Camboriu CP 20 CEP 88.340.000 Santa Catarina, Brazil)
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