Fishmeal replacement using housefly larvae meal as protein ingredient in balanced feeds for bullfrog tadpoles and froglets (Lithobates catesbeianus)

This research evaluates the use of housefly larvae meal (HLM) as an alternative protein replacing fishmeal (FM) present in feeds for bullfrog tadpoles and froglets. The treatments consisted of the formulation of four feeds for tadpole stage with 30 % of protein and four inclusion percentages of HLM (T300 – 0 %; T3025 – 25 %; T3050 – 50 %; T3075 – 75 %). Likewise, for pre-fattening stage (froglet), four feeds with 40 % of protein and the same inclusion percentages of HLM were managed (T400 – 0 %; T4025 – 25 %; T4050 – 50 %; T4075 – 75 %). Weight gain (WG), survival rate (SR), feed conversion rate (FCR), protein efficiency rate (PER) and metamorphosis process (start and duration) were established as response variables. Statistical analyses were performed using ANOVA and Tukey's test. The results suggest that in the tadpole stage T3025 contributes more to weight gain (4401.39 ± 36.66 %) and metamorphosis process (started at 35 ± 0.5 and duration of 169 ± 7 hours). On the other hand, T3050 did not show differences with respect to T300 for WG and start of metamorphosis. In the pre-fattening stage, treatments T400 and T4025 presented outstanding values in WG (154.13 ± 5.91 and 149.80 ± 6.33 %, respectively) and SR (88.3 ± 1.2 and 87.6 ± 1.5 %, respectively). Finally, considering the productive performance at the end of both stages, the diets with 0 and 25 % inclusion of HLM did not show differences for the variables of WG, FCR and PER. The values obtained suggest that HLM has nutritional characteristics that allow it to replace fishmeal between 25–50 % in the formulation of balanced feeds for bullfrog culture