Transformation Capability Optimization and Product Application Potential of Proteatia brevitarsis (Coleoptera: Cetoniidae) Larvae on Cotton Stalks

Abstract

Cotton stalks (CS) are a potential agricultural biomass resource. We investigated the use of CS as a feed for Proteatia brevitarsis Lewis larvae and the resulting frass (larvae dung-sand) as a fertilizer. Based on a three-factor experiment (decomposition inoculant, fermentation duration, and cattle manure ratio), the optimal parameters for the transformation of CS using P. brevitarsis larvae were determined as 40–50% of cattle manure, the use of VT inoculant and a fermentation duration of 25–30 days. Regarding the products of the transformation, the protein content of the larval body was as high as 52.49%, and the fat content was 11.7%, which is a suitable-quality insect protein source. The organic matter content of larvae dung-sand was 54.8%, and the content of total nitrogen, phosphorus, and potassium (TNPK) was 9.04%, which is twice more than that of the organic fertilizer standard (NY525-2021, Beijing, China, TNPK ≥ 4.0%), and larvae dung-sand has the potential of fertilizer application. Therefore, CS as a feed and fertilizer based on the transformation of P. brevitarsis larvae is feasible, and it is a highly efficient way to promote the utilization of both CS and cattle manure.