Optimum protein level for growth in juvenile bullfrog (Rana catesbeiana Shaw, 1802)

An estimate was made of the optimum protein level in growth diets for bullfrog Rana catesbeiana. A nested design of six treatments with three replicates per treatment was used. Juvenile bullfrogs (8.84 ± 1.42 g average initial weight) were fed in lots at 6% body weight per day with six practical diets containing 20, 28, 34, 42 50 or 58% crude protein from fish meal. Each batch contained 12 frogs placed randomly in plastic cages with an automatic water sprinkler system to keep the animals wet and the cages clean. Cages were installed under a controlled environment: 28 °C temperature; 100% relative humidity; and 14L:10D photoperiod. The diets were assigned randomly to the cages. Results were evaluated in terms of survival, growth and feed efficiency. All the treatments showed 83% survival except the 28% protein diet, which had 60.44%. Productive performance tended to improve as protein level increased. The greatest growth was observed in the 58% protein diet, although this was not statistically different from the 42 and 50% protein diets. Feed conversion ratio (FCR) also improved as dietary protein level increased, with the best FCR in the 58% protein diet, although this was not significantly different from the 42 and 50% protein diets. Optimum protein level was estimated using a second-order quadratic regression using weight gain (%) and established as 39.21% crude protein at a protein:energy ratio of 81.34 mg P/kcal. Under the experimental conditions applied, a 40% crude protein level is recommended for growth in juvenile R. catesbeiana.