Suplementação de vitamina C em rações para reversão sexual da tilápia do nilo

Abstract

The effects of vitamin C supplementation (0; 50; 100; 200; 400; 600; 800; 1,000 mg kg-1 of diet) on diets for sex reversal of the Nile tilapia, Oreochromis niloticus, were evaluated on groups of 600 larvae stocked in 0.08 m3 hapas and fed for 30 days with hormone-treated feeds containing different supplementation levels (n=3). Weight gain and total length increment were evaluated after days 0, 10, 20 and 30. Survival rate (S%) and sex reversal rate (SR%) were determined at the end of the experimental period. Weight gain and total length became significantly different only after day 20 (P<0.0001). Best results for weight gain were attained with dietary vitamin C levels above 800 mg kg-1, while the best results for growth in length were attained with dietary vitamin C levels above 400 mg kg-1. Levels of supplementation higher than 200 mg kg-1 did not lead to better survival rates. SR% values were not significantly affected by vitamin C supplementation of sex reversal diets (P<0.9993). Optimal values for vitamin C supplementation of sex reversal diets for the Nile tilapia, derived from polinomial regression analysis procedures, were: weight gain 859.5 mg; growth in length 765.0 mg, and for survival rate 685.7 mg.