As an economic activity, aquaculture presents the greatest growth in the current livestock sector; in Costa Rica, tilapia production represents 80% of total aquaculture production. Most aquaculture producers are small rural enterprises that generally do not have access to feed alternatives for the initial phases of tilapia development, thus, evaluation of economic feed alternatives that can be produced and processed in-situ is of interest. The research was carried out for 46 days to evaluate the effect of three replacement levels of dry matter consumption of balanced feed by red worm (Eisenia foetida), on zootechnical parameters and tissue composition in the initial stages of blue tilapia (Oreochromis aureus), where a completely randomized design of one factor and three repetitions per level was used, 12 experimental units were established with a total of eight hormonally reverted tilapia in each one, with an initial weight of 3.25 ± 0.35. Four treatments were used: the control treatment (T0), which was composed entirely of balanced feed, and three balanced feed substitution treatments by dehydrated worms, in percentages of 25% (T1), 50% (T2) and 75% (T3) of the dry matter (Table 1).
The parameters of total weight gain (GPT), standard length increase (iSL), condition factor (K), specific growth rate (TCE), feed conversion rate (FCR), and protein efficiency ratio (PER) were measured every two weeks, as well as cumulative mortality. At the end of the experiment, the biochemical composition of the fish did not show significant differences by treatment, indicating that it was not affected by the substitution with dehydrated worm. Significant differences were observed between treatment T3 and T0, for GPT, iSL, TCE, FCR and PER (Table 2).
For this reason and taking into consideration the results of the rest of the parameters, it was determined that up to 50% (dry matter basis) of E. foetida can substitute balanced feed in the daily ration for fingerlings Oreochromis aureus without affecting the zootechnical parameters analyzed or the chemical composition of the animals under optimal water quality conditions. However, it is necessary to carry out more research on relevant aspects of the use of worms as a nutritional input, such as: digestibility, anti-nutritional properties and greater detail in nutritional profiling.