In vitro crude protein digestibility of Tenebrio molitor and Hermetia illucens insect meals and its correlation with chemical composition traits

The aims of this study were to evaluate the correlation between in vitro crude protein digestibility coefficients of insect meals from Tenebrio molitor (TI) and Hermetia illucens (HI) and their chemical composition traits as well as to develop regression equations able to estimate the in vitro crude protein digestibility (CPd) from proximate analysis of insect meals. Twelve samples of insect meals (6 from TM larvae, TM 1-6 and 6 from HI larvae, HI 1-6) were obtained from different producers and analysed for chemical composition and in vitro crude protein digestibility by a two-step enzymatic method (digestion with pepsin and trypsin-enriched pancreatin). For both insect meal samples, CPd was negatively correlated to ADF and chitin contents, while just for HI there was a positive correlation (P<0.01) between CP percentage of the samples and CPd. For both insect meals the former variable chosen in the stepwise analysis was the chitin, explaining the 79.45% of CPd variability for Tenebrio molitor samples and the 98.30% for Hermetia illucens. In the second step, the amount of protein linked to ADF was added in the model for T. molitor and CP for H. illucens samples. The coefficients chitin is the main constituent of insect body able to affect the crude protein digestibility of Tenebrio molitor and Hermetia illucens larvae meals estimated by an in vitro enzymatic method.