Sincronização e indução hormonal na reprodução de tilápia do Nilo (Oreochromis niloticus)

Abstract

Studies related to reproductive synchronization have been developed, however, there are no protocols established in tilapia under the circumstances of hormonal induction and different distributions and days. The objective of this study was to evaluate the possibility of sexual synchronization of Nile tilapia (Oreochromis niloticus) under different distributions and days. This study was carried out in the fishery sector of the Federal University of Lavras, for a period of 21 experimental days that began at the end of March and beginning of April. It was conducted in a randomized complete block design (DBC), in a factorial scheme 2 × 2 × 3, (male and female, with and without hormone induction, and three times 7, 14 and 21 days). A total of 324 fish were used, 180 females and 144 males, previously microchipped with 250 ± 12.25 g of body weight. The animals were distributed in 9 masonry tanks with continuous flow water supply. The distribution of the animals in the tanks was: 3 tanks with 36 males, 3 tanks with 36 females and another 3 tanks containing 12 males and 24 females, separated by a glass and screen in the bottom. After the experimental period, the human chorionic gonadotrophin hormone hCG was applied in half of the animals (males and females) by intramuscular injection at a concentration of 5 IU / g fish live weight. In half of the remaining animals from each treatment, the same saline dosage was applied. The animals were evaluated at 7, 14, and 21 days. After 667 hours-degrees after the application of the hormone were carried out extrusion and spermization by means of celomática massage. Females were observed that showed ease in the release of gametes, and spawning index, absolute and relative fecundity, oocyte diameters and germinal vesicle peripheral position were evaluated. In males, sperm concentration, seminal volume, motility, duration of sperm motility, and sperm integrity were evaluated. The data were submitted to analysis of variance at the 5% level of significance. For females at 14 days there was greater ease of extrusion when separated from males, with application of the hormone. The distribution influenced the spawning weight, the larger diameter, and for the diameters smaller the days and induction presented interference. In males, the days interfered in the increase in volume and duration of semen motility independent of induction and environment, and finally, the environment interfered significantly in semen concentration.