Abstract / Description
Modulating feed buffering capacity via diet formulation is of increasing interest in livestock due to its ability to regulate gastrointestinal conditions and nutrient utilisation. This study hypothesises that dietary macronutrient composition and calcium carbonate (CaCO3) modulate fish gut microbiota, potentially improving the effects of feed buffering capacity. Thus, it explores the relationship between microbiota modulation and chyme changes induced by different protein-to-energy (P:E) ratios (16.1 vs 26.4 mg/kJ) and CaCO3 supplementation in diets of rainbow trout (Oncorhynchus mykiss, 284 ± 2.5 g). This multifactorial experiment also evaluated the effect of gut region (proximal vs distal) and postprandial time (3 vs 7 h). After a 6 week feeding trial, none of the tested factors showed differences in estimated microbial richness (Chao1 index, P > 0.05), while the proximal intestine exhibited higher microbial diversity (Simpson index) than the distal gut (P = 0.007). In addition, inter-individual microbial variability was significantly different between intestinal regions, qualitatively (Jaccard distance; F = 7.98, R2 = 0.05, P = 0.001) and quantitatively (Bray-Curtis distance; F = 96.19, R2 = 0.40, P = 0.001), which was correlated with differences in chyme pH, relative water and mineral fluxes, and CP apparent digestibility (P