Effects of Replacing Soybean Meal With Black Soldier Fly Larvae on In Vitro Gas Production Kinetics, Rumen Fermentation, and Rumen–Abomasum Degradability Using an Ankom Daisyii Incubator

This study investigated the effects of replacing soybean meal (SBM) with black soldier fly larvae (BSFL) in powdered and pelleted forms at varying levels in ruminant diets on in vitro gas production kinetics, rumen-abomasum degradability, and fermentation characteristics using the Ankom DaisyII incubator. A 2 × 4 + 1 factorial arrangement within a completely randomised design was used, comprising two physical forms of BSFL (powdered and pelleted) and four levels of SBM replacement in the concentrate (25%, 50%, 75% and 100%), in addition to a control group without BSFL. Compared to BSFL, SBM exhibited higher in vitro dry matter degradability and rumen degradable protein, but lower rumen undegradable protein, than either BSFL form. Gas kinetics and cumulative gas volume after 96 h were significantly influenced (p < 0.01), with the highest gas production from the immediately soluble fraction observed at 100% pelleted BSFL. At 25%-50% replacement with pelleted BSFL, gas production potential and total gas volume were reduced compared to the control. Ammonia-nitrogen concentrations peaked at 18.7 and 24.4 mg/dL after 24 and 48 h, respectively, with 100% pelleted BSFL. In vitro dry matter degradability was lowest with 75% powdered BSFL (35.0% dry matter) and 100% pelleted BSFL after 48 h. The highest abomasal degradability occurred at 25% BSFL inclusion. Both forms of BSFL significantly reduced acetic acid and increased propionic acid concentrations (p < 0.01). The greatest reductions in methane production were observed with 50% powdered BSFL and 75%-100% pelleted BSFL inclusion levels. In conclusion, replacing SBM with BSFL in ruminant diets enhanced fermentation efficiency and reduced methane production, with the pelleted form offering more favourable results across key parameters.