Óleos essenciais na alimentação de reprodutores de Tilápia-do Nilo (Oreochromis niloticus)

Abstract

Were realized two experiment to evaluate the effects of essential oils addition (oregano, pepper, cinnamon and rosemary), in the initial fase and reproduction of Nile tilapia (Oreochromis niloticus). The experiment were performed at the Universidade do Oeste do Paraná, between January 2010 to March 2011. The first experiment observed the fingerlings performance (males and females not sexual reversed) and the second experiment the female reproductive performance. In experiment 1 were used 1.300 fingerlings with initial weight (13,66 ± 0,16 g), distributed in 20 hapas with 3X2 meters. The design treatment was completely randomized design consisting of five treatments and four repetitions. The treatments had the inclusion of five different additions of the essential oils (0,00; 0,25; 0,50; 0,75 and 1,00 ppt). The fishes were fed on isonitrogenous and isocalorics diets, containing, 30% digestible protein (DP) and 3000 kcal of digestible energy (DE).kg feed-1. The parameters evaluated in treatment 1 were initial mean weight, final mean weight, standard length, weight gain, daily weight gain, specific growth rate, feed conversion and survival factor. These parameters were not affected by treatments (P>0.05). Among the body indexes evaluated, hepato-somatic index (HSI), viscero-somatic index (VSI) and gonado-somatic index (GSI), were observed effect on HSI (P<0.05), that growing because the additive inclusion. At the same time, the average area of hepatocytes was not affected (P>0.05). The bromatological parameters, gonadal crude protein (CP), gonadal fat (FA), carcass dry matter (DM), carcass CP and liver CP were not affected (P>0.05). In second experiment, 560 fishes were used for initial weight 90,85±2,53g. The females were stored in 20 "hapas" 3mx2m, adding 21 females in each "hapa". The males used for breeding were stocked in 20 "hapas" 2mX1m adding 7 males by "hapas . The rations, isonitrogenous (32% CP) and isocalorics (3200 kcal DE.kg-1), were pelleted. The same inclusion of essential oils and design experiment 1 was applied. During the second experiment, were observed feed intake, condition factor, feed conversion, biomass gain, somatic index (HSI, VSI, GSI), initial and final weight, specific growth rate and survival. Only gonadosomatic index was changed (P<0.05). The parameters of reproductive performance and offspring`s quality measured were an average diameter of eggs (mm), absolute fecundity, relative fecundity, relative efficiency index of eggs and larvae, egg weight (mg), production of larvae hatching rate (% ), survival rate to fasting, egg volume (mL) and relative larval production. These were not affected by treatments (P>0.05). The blood calcium and glucose levels (mg.dL-1) of female Nile tilapia of experiment two were not affected by treatments (P>0.05). The inclusion of the essential oils in rations to Nile tilapia did not promote changes on the performance in the initial fase (experiment 1). However, levels above 0.50ppt, increased the female liver weight (HSI) in experiment 1. In experiment 2, the inclusion until 1ppt not provided any adverse effect on the animal performance or reproductive aspects, although additions of 0.25 ppt promote better GSI