Insect meal in ruminant nutrition: in vitro fermentation characteristics and comparison with conventional protein source

This research aimed to evaluate the nutritional composition, in vitro digestibility, and gas production kinetics of Hermetia illucens (HI) and Tenebrio molitor (TM) processed proteins compared with soybean meal f.e. as a reference raw material. Nutritional characterization and in vitro ruminal fermentation tests were performed to determine in vitro short-chain fatty acids production, the gas production profile and methane production. HI and TM were both full fat meal with a mean protein content of 41 and 61 % respectively and the soybean meal had 45 % of crude protein. Total gas production (value expressed in mL as mean ± SD) was lower for both HI (27±4.5) and TM (23±3.3) processed proteins compared to soybean meal (77±2.1). Similarly, differences have been observed in the case of short-chain fatty acids production which was higher when soybean meal was used as substrate than with HI and TM. However, when considering fatty acid molar proportion differences were observed only in case of propionate, isobutirate, isovalerate, and valerate. Interestingly methane production (value expressed in µmol as mean ± SD) was lower for insect processed proteins (HI 70±15; TM 59±4.5) compared to soybean meal (282±7.6). Obtained results indicated that insect processed proteins hereby tested were characterized by low fermentation profile, thus it might speculate that they could represent a valid by pass protein source.