Background Insects, such as Hermetia illucens larvae, are rich in chitin and proteins, and represent a suitable feed ingredient replacement for animals. However, little is known about the effect of administering H. illucens larvae on intestinal microbiota, bacterial metabolite profiles, and mucosal immune status in animals. This study aimed to investigate the effects of administering H. illucens larvae on colonic microbiota and bacterial metabolites production in finishing pigs. Seventy-two crossbred (Duroc × Landrace × Large White) female pigs (initial body weight, 76.0 ± 0.52 kg) were randomly allocated to three different dietary treatments: a control diet (Control group) and two diets corresponding to 4% (H1 group) and 8% (H2 group) H. illucens larvae inclusion levels, respectively. Each treatment consisted of eight pens (replicates), with three pigs per pen. After 46 days of feeding, eight pigs per treatment ( n = 8) were slaughtered, and the colonic digesta and mucosa were collected for microbial composition and microbial fermentation products, and genes expression analyses. Results The results showed that the H1 diet significantly increased the abundance of Lactobacillus , Pseudobutyrivibrio , Roseburia , and Faecalibacterium compared with those in the control group ( P < 0.05), with a decrease in the abundance of Streptococcus . The numbers of Lactobacillus , Roseburia , and Clostridium cluster XIVa were significantly greater in the H1 group than in the control group ( P < 0.05). Meanwhile, H2 diet increased the number of Clostridium cluster XIVa compared with the control group ( P < 0.05). For colonic metabolites, total short chain fatty acids, butyrate, and isobutyrate concentrations were significantly higher in the H1 group than those in the control group ( P < 0.05); the H1 treatment caused a striking decrease in protein fermentation compared with the control group, as the concentrations of total amines, cadaverine, tryptamine, phenol, p -cresol, and skatole were significantly lower ( P < 0.05). Additionally, H2 diet also increased butyrate concentration compared with control group ( P < 0.05), while decreased the concentrations of phenol, p -cresol, and skatole ( P < 0.05). Pigs in the H1 group down-regulated the expression of TLR -4 and pro-inflammatory cytokines ( IFN-γ ) compared with pig...

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Chemical deformation (chemical shrinkage/expansion), the absolute volume change during reactions, is a key parameter influencing the volume stability, especially the autogenous deformation of a binder material. This work, for the first time, reports an in-depth investigation on the chemical deformation of metakaolin based geopolymer (MKG). Unlike ordinary Portland cement-based binders with monotonic chemical shrinkage, MKG experiences three stages of chemical deformations: chemical shrinkage in the first stage, chemical expansion afterward and chemical shrinkage again in the final stage. Various experimental techniques (XRD, FTIR and NMR) plus theoretical calculations are applied to explore the mechanisms behind the chemical deformation of MKG. Clear correlations are found between the chemical deformations and the reaction processes during geopolymerization. A conceptual chemical deformation model for geopolymer is summarised. The insights into the chemical deformation provided by this study will play a fundamental role in further understanding, controlling and even utilizing the deformation behaviours of geopolymers.

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