Use of dietary frass from black soldier fly larvae, Hermetia illucens, in hybrid tilapia (Nile x Mozambique, Oreocromis niloticus x O. mozambique) diets improves growth and resistance to bacterial diseases

Abstract

Frass, a by-product of the larval meal industry, is heterogeneous and includes larval excrement, exoskeleton sheds and residual feed ingredients along with abundant nutrients, chitin and beneficial microbes. The present study was performed to evaluate the changes in growth, feed utilization, body composition, hematology, serum chemistry, immune responses and disease resistance of hybrid tilapia, Nile x Mozambique (Oreocromis niloticus x O. mozambique) fed diets containing frass from black soldier fly larvae, Hermetia illucens. Five diets containing frass at levels of 0, 5, 10, 20, and 30% as partial replacements of a combination of soybean meal, wheat short and corn meal on an equal protein basis were fed to juvenile hybrid tilapia (2.6 ± 0.035 g) in quadruplicate aquaria to apparent satiation twice a day for the first two weeks and once daily for rest of the feeding trail. Final weight gain was significantly increased in fish fed the diet including the highest level of frass (30%). Fish fed diets containing frass (5% to 30%) had significantly higher protein efficiency than the group fed diet without frass (control diet). Feed intake and feed utilization efficiency were not significantly affected by dietary treatments. Survival during the feeding trail, whole-body composition, hematological parameters, and serum biochemistry were not affected by dietary treatment. Serum complement activity of fish fed 30% dietary frass was significantly higher than that of fish fed other treatments. Fish fed the diets containing frass showed significant dose-dependent trends in survival against both Flavobacterium columnare and Streptococcus iniae challenges. Frass from the larvae of black solder flies fed Distillers’ dried grains with solubles has potential for use as feed ingredient for improving growth of hybrid tilapia. Use of frass in tilapia diets may prove beneficial by improving innate immune components and the resistance of hybrid tilapia against bacterial infection.