Acceptance and forage utilization responses of steers consuming low-quality forage and supplemented black soldier fly larvae as a novel feed

Abstract

As the insect-rearing industry scales in the United States and other developed nations, it has the potential to create multiple product streams (e.g., oil and protein-rich biomass) for existing markets. Black soldier fly larvae (BSFL; Hermetia illucens) has been identified as a potential livestock feed because it is not expected to compete in the human food sector and its production has a lesser environmental footprint than that of conventional feeds. Existing research on BSFL as feed focuses on full-fat BSFL for poultry and aquaculture. Therefore, the objective of our experiment was to evaluate the viability of defatted BSFL as an alternative protein source for beef cattle consuming forage. Procedures were approved by Texas State University IACUC (#7726). Two experiments were conducted using ruminally cannulated beef steers fed low-quality forage in 5 × 5 Latin squares. Experiment 1 assessed consumption of BSFL as a protein supplement and included five 5-d periods with 3-d for washout and 2-d for measurement of supplement intake and preference. There were five treatments delivered in addition to the basal forage: 100% soybean meal (SBM); 75% SBM/25% BSFL; 50% SBM/50% BSFL; 25% SBM/75% BSFL; and 100% BSFL. Supplement and forage intake did not differ between treatments (P ≥ 0.45) nor was there a treatment × day interaction (P ≥ 0.45). Experiment 2 evaluated the effect of BSFL supplementation on forage (5.3% crude protein) intake and digestion and included five 14-d periods with 8-d for treatment adaptation, 5-d for measurement of intake and digestion, and 1-d for determination of ruminal fermentation. There were four treatments of supplemental BSFL provided at graded N levels: 0, 50, 100, or 150 mg N/kg BW and one level of SBM at 100 mg N/kg BW. Increasing provision of BSFL linearly increased forage organic matter (OM) intake (P = 0.04), total OM intake (P < 0.01), total digestible OM intake (P < 0.01), dry matter digestibility (P = 0.01), and OM digestibility (P = 0.02). There were no significant differences (P ≥ 0.17) in intake or digestibility between levels of BSFL and SBM. Ultimately, defatted BSFL has potential to replace conventional feeds as a protein supplement without sacrificing forage utilization.