Effects of heat treatment on rumen degradability and protein intestinal digestibility of black soldier fly (Hermetia illucens L.) in goat

The black soldier fly larvae (BSF) are used as a substitute for soybean meal due to their high crude protein content. This experiment aims to assess the impact of heat treatment on the rumen degradability of BSF and protein digestion in the small intestine using the in situ nylon bag method and the three-step in vitro method. This study comprises a total of 8 groups (n = 6). The negative control group includes only full-fat soybeans (FFS) and BSF (FF group and BS group). The positive control groups consist of a 95% BSF or 95% FFS mixed with 5% cassava (FFC and BSC groups). The treatment groups involve adding 75% water to the positive control mixture, followed by vigorous kneading to achieve uniform mixing. The resulting mixture was then pressed to a thickness of approximately 5 cm, placed in an oven, and dried for 120 min at temperatures of 120 °C and 140 °C (12FFC, 14FFC, 12BSC, and 14BSC groups). Nylon bags will be incubated in the rumen for 0, 2, 4, 8, 12, 24, and 48 h, and the small intestine protein digestion rate will be analyzed at 16 h. Compared to the BS group, heat-treated BSF showed increased (P < 0.05) rumen DM degradability and effective degradability. The 14BSC group increased (P < 0.05) rumen CP degradability and degradation kinetic parameters, while the 12BSC group decreased (P < 0.05) these parameters. The CP degradability of BSF was significantly higher (P < 0.05) than that of full-fat soybeans. The Idg and IDCP of heat-treated full-fat soybeans were significantly higher (P < 0.05) than those of other treatment groups. At the same time, heat treatment was beneficial for increasing (P < 0.05) the Idg and IDCP of BSF, and the 14BSC treatment effect was significantly better (P < 0.05) than that of the 12BSC group. Therefore, based on the results of this experiment, it is recommended to supplement BSF with cassava and subject them to heat treatment at 140 °C.