**Background:** Fish meal and soybean meal are widely used protein sources in swine feed, but price fluctuations have increased demand for alternatives such as insect protein. Black soldier fly larva (BSFL) meal is a promising alternative due to its high crude protein concentration. However, BSFL may be contaminated with microorganisms including Salmonella, Escherichia coli, Staphylococcus aureus, and Bacillus cereus due to rearing conditions, necessitating disinfection processes. Drying methods (hot-air, microwave, freeze drying, roasting) and blanching pretreatments are used to reduce microbial risk and increase shelf life, but their effects on nutrient utilization in pigs are poorly understood. In vitro assays correlate well with in vivo experiments and offer a practical approach to evaluate nutrient digestibility.
**Methods:** BSFL were reared at 25-32°C and 60-70% relative humidity for 15 days on dried food waste. Four BSFL meals were prepared: (1) microwave drying at 80°C for 32 min; (2) hot-air drying at 60°C for 17 h; (3) blanching in boiling water for 5 min followed by hot-air drying at 60°C for 17 h; and (4) blanching in 2% citric acid solution for 5 min followed by hot-air drying at 60°C for 17 h. After drying, oil was extracted at 45°C using a screw-type cold press. A 2-step in vitro procedure simulated stomach (pepsin, pH 2.0, 39°C, 6 h) and small intestine (pancreatin, pH 6.8, 39°C, 18 h) digestion to measure IVID of DM, N, and AA. A 3-step procedure added a large intestine phase (multi-enzyme solution, pH 4.8, 39°C, 18 h) to measure IVTTD of DM and OM. Chemical analyses included DM, N, OM, ether extract, ash, ADF, chitin, and amino acids. Statistical analysis used SAS GLM procedure with Tukey's adjustment (p < 0.05).
**Key Results:** Nitrogen concentrations ranged from 8.5 to 9.4% and ether extract from 6.9 to 11.5% on an as-is basis. Lysine ranged from 2.80 to 3.24% and methionine from 0.71 to 0.89%. Hot-air-dried BSFL meal had significantly greater IVID of N (86.7%) compared with microwave-dried BSFL meal (84.4%; p < 0.05). Blanched BSFL meals in water (81.3%) or 2% citric acid (82.5%) had significantly lower IVID of N than both microwave-dried and hot-air-dried meals (p < 0.05). IVTTD of DM was significantly higher for microwave-dried (90.4%) and hot-air-dried (89.6%) meals compared with water-blanched (85.0%) and citric acid-blanched (84.5%) meals (p < 0.001). IVTTD of OM was highest for hot-air-dried (86.6%), followed by microwave-dried (85.7%), then citric acid-blanched (81.5%), and lowest for water-blanched (80.6%) (p < 0.001). For indispensable amino acids, hot-air-dried BSFL meal showed significantly higher IVID for Arg (96.5%), Ile (94.0%), Leu (92.8%), and Thr (92.7%) compared with microwave-dried (94.4%, 91.5%, 90.7%, 90.8%, respectively) and both blanched meals (p < 0.05). Blanched meals had significantly lower IVID for all amino acids compared with non-blanched meals. The IVID of His, Lys, Met, and Phe did not differ significantly between microwave-dried and hot-air-dried meals but were significantly lower in blanched meals.
**Clinical Implications:** This study provides the first documentation of in vitro amino acid digestibility in BSFL meal for pigs. Hot-air drying at 60°C for 17 h is recommended over microwave drying for producing BSFL meal with higher nutrient digestibility. Blanching in water or citric acid solution, despite potential antimicrobial benefits, significantly reduces nitrogen and amino acid digestibility, likely due to increased chitin concentrations (7.1-7.2% in blanched meals vs. 4.3-4.8% in non-blanched meals). Chitin is poorly digested by pigs' endogenous enzymes and negatively correlates with nutrient utilization. The findings directly inform commercial production decisions for insect-based swine feed, suggesting that hot-air drying without blanching optimizes nutrient availability. However, the trade-off between microbial safety and nutrient digestibility requires further investigation, as blanching may still be necessary for pathogen control depending on rearing conditions.