Comparison of four bullfrog (Rana catesbeiana Shaw, 1802) rearing systems: Tanque-Ilha, Confinamento, Anfigranja, and Gaiolas. 1. Gain in weight; 2. Operational cost

In the experimental outdoor facilities planned for frog culture in the Fishery and Frog Culture Station of Pindamonhangaba, Sao Paulo State, Brazil (22 degree 55' 55" S and 45 degree 27' 22" W), the gain in weight of bull-frogs and the operational cost of four rearing systems: Tanque-Ilha, Confinamento, Anfigranja, and Gaiolas, were studied. The methodology attended the specifications preconized by the authors of the systems, and they have in common the same animal density and the same food and physical management of the animals. The experimental design was that of a total randomised experiment with four treatments, represented by each one of the systems, and four repetitions. For the analysis of the results, the data were adjusted by a model that includes the effects of the systems and the size of the animals, by the initial number of frogs, through the analysis of covariance. The data were processed by the HARVEY's minimum square method. The conclusion indicated that the Tanque-Ilha system was that which rendered a greater gain in the mean weight of the frogs, that means, 17.9% more than the Anfigranja system, 43.2% more than the Confinamento system, and 172.6% more than the Gaiolas system, by a cost of Cr$ 1,970.00 (US$ 1.14) per kilogram of alive frog. This work also evidenced the importance, for frog culture, of the practice by separating the animals in different groups of size for cannibalism control, and the effect of the environmental temperature on the gain in weight, showing that these two aspects should be object of further investigations.