Nutritional analysis of alternative feed ingredients and their effects on the larval growth of Tenebrio molitor (Coleoptera: Tenebrionidae)

Abstract

Alternative feeds comprising only brewer's spent grain (BSG) or distillers dried grain (DDG), both agricultural byproducts, and 50% BSG or 50% DDG mixed with 50% wheat bran (WB) were compared to the standard 100% WB feed provided to Tenebrio molitor larvae to evaluate their effects on the nutritional quality and economic viability of mass-producing this insect. Crude protein content was highest in larvae fed on 100% WB and 100% DDG, and the latter had 2.32 and 1.88 times more essential and non-essential amino acids than the 100% WB group, respectively. Larvae fed on 50% DDG+50% WB had 1.30 times more saturated fatty acids but 1.08 times less unsaturated fatty acids and 1.03-1.23 times less potassium, phosphorus, and magnesium than larvae fed on 100% WB. Traces of mercury were detected in larvae fed on 100% WB and 50% DDG+50% WB, although at levels below the General Food and Feed Standard (Ministry of Food and Drug Safety, Republic of Korea), but neither Escherichia coli or Salmonella spp. were detected in the feeds. Larval and pupal weight, larval development and survival, and pupation rate were higher in larvae fed on 50% BSG or 50% DDG mixed with 50% WB groups than in larvae fed on 100% WB. Therefore, using 50% BSG or 50% DDG mixed with 50% WB as an alternative feed in the mass production of T.molitor provides higher quality larvae at a lower cost than does using the conventional 100% WB feed.