Nutritional evaluation of frass from black soldier fly larvae as potential feed ingredient for Pacific white shrimp, Litopenaeus vannamei

Abstract

Frass is a by-product of the larval meal industry and is currently readily available and competitively priced relative to larva meal. In addition to generally high protein and fat content (21.6% and 6%, respectively), frass contains abundant nutrients, chitin, and beneficial microbes. This study evaluates the effect of various levels of frass derived from the larvae of black solder flies fed dried distillers’ grains (DDG) with solubles on growth performance, whole body and fillet proximate compositions and selected hemolymph parameters of Pacific white shrimp, Litopenaeus vannamei. Five isocaloric diets containing frass at levels of 0%, 5%, 10%, 20% and 30% as partial replacement of a combination of soybean meal (SBM), cottonseed meal (CSM), wheat short (WS) and corn meal (CM) on an equal protein basis were offered four times daily to Pacific white shrimp. Four replicate groups of 15 shrimp per tank (initial weight 4.06 ± 0.05 g) were offered experimental diets at 4% total body weight daily for 12 weeks. Shrimp in each aquarium were group-weighed and counted at 2-week intervals and feed inputs were adjusted based on observed survival and weight gain. Although no significant differences were observed in final weight gain, survival, and whole-body composition of shrimp among treatments, there appeared to be quadratic trend of growth with increasing dietary levels of frass. Shrimp fed diets with 5% frass, and 30% frass, showed the highest and lowest weight gain, respectively. Percent lipid content of fillet is linearly decreased with increasing dietary levels of frass and shrimp fed 20% and higher dietary frass level had significantly lower level of fillet lipid. Serum from shrimp fed 20% dietary frass significantly increased inhibition of Vibrio parahaemolyticus growth when compared to that of the control group. However, other hemolymph parameters (total hemocyte count, hemocyanin, serum protein and serum cholesterol) were not significantly affected by dietary treatments. Frass can be incorporated in shrimp diets up to 30% as a substitute for a combination of SBM, CSM, WS and CM without affecting their growth performance, body composition, hemolymph parameters.