Abstract
We sought to assess whether incorporating the frass of black soldier fly Hermetia illucens larvae in Channel Catfish Ictalurus punctatus diets affects fish growth, serum biochemistry, intestinal histology, and survival against bacterial pathogens.
Three experimental diets were formulated, with commercial black soldier fly larva frass (BSFF) added into the formulation at 0.0, 7.5, and 15.0%. Fifty Channel Catfish fingerlings (average initial weight ± SD = 3.04 ± 0.07 g) were stocked into 15 glass aquaria within an indoor recirculating aquaculture system. Diets were randomly assigned and offered to catfish in five replicate aquaria. After the conclusion of the 84-d experiment, fish were group-weighed and counted to evaluate growth and survival. In two other experiments, juvenile catfish were acclimated to the experimental diets for 90 and 47 d, respectively, and then challenged with pathogenic bacteria. Immersion challenges were performed with Edwardsiella ictaluri (3.1 × 105 CFU/mL), virulent Aeromonas hydrophila (2.7 × 107 CFU/mL), or Flavobacterium covae (1.0 × 106 CFU/mL).
No significant differences were observed among treatments in terms of final biomass, final weight, weight gain (%), or survival. However, fish that were offered 7.5% and 15.0% BSFF in their diets had significantly lower feed conversion ratios (1.40 and 1.46 for 7.5% and 15.0% BSFF, respectively) than fish offered the basal diet (1.58). Fish challenged with E. ictaluri exhibited better survival when offered feed with BSFF. However, the inclusion of BSFF in the diets did not significantly influence the postinfection survival of fish challenged with virulent A. hydrophila or F. covae.
We found that BSFF can be used in Channel Catfish diets without adversely affecting growth or survival and that BSFF can also confer protective benefits to Channel Catfish against E. ictaluri.