Parâmetros reprodutivos para sincronização em tilápia-do-nilo (Oreochromis niloticus) alimentadas com dietas com diferentes níveis nutricionais

Abstract

Nile tilapia (Oreochromis niloticus) presents split spawning and reproduces naturally in captivity throughout the year, under appropriate conditions. It displays reproductive limitations such as low fecundity and asynchronous maturation, which may be controlled by various biotic and non-biotic factors, including nutrition. Therefore, the objective of this work was to evaluate reproductive parameters for synchrony of tilapia nourished through different nutritional level diets. Three hundred and twenty tilapia females with an average weight of 229.35±1.82g were used. After morphometric analysis the females were randomly distributed in 16 polyethylene boxes, each having 500L capacity under a water recirculation system and controlled temperature of 27 o C. An entirely random design in a 2 × 2 factorial scheme at a density of 20 animals per box was applied. Treatments consisted of two types of feed (32 and 40% of crude protein) at 2 evaluation periods (14 and 28 days) with 4 replications. The following parameters were assessed: spawning weight (g), oocyte diameter (mm), oocyte percentage displaying germinal vesicle at peripheral position (GVPP%), celomic cavity length (M1, M2 and M3 in cm), gonadosomatic index (GSI%), hepatosomatic index (HIS%), spawning index (DI%), absolute frequency (AF), red blood cells (10 6 µl), glucose (mg dL -1 ), hematocrit (%) and protein (mg dL -1 ). The obtained results underwent variance analysis and the average values were compared via T test through SAS ® , at a statistical significance level of 5% (p<0.05). No statistical differences were observed at 32 and 40% crude protein level for all evaluated parameters (p>0.05). In relation to data collect period (14 and 28 days), statistical differenc es were verified for the celomic cavity length in centimeters (M1), hematocrit percentage (%), protein concentrations (mg dL -1 ) (p<0.05). The currently used treatments were not efficient for tilapia female reproduction synchrony under the employed conditions.