4.6. Fecal Short-Chain Fatty Acid Quantification

Concentrations of acetate, propionate, iso-butyrate, butyrate, and iso-valerate were assessed according to Bassanini et al. [65]. The measurement of SCFAs was performed by gas chromatography, using a Varian model 3400 CX Gas chromatograph fitted with FID detector, split/splitless injector, and a SPB-1 capillary column (30 m × 0.32 mm ID, 0.25 μm film thickness; Supelco, Bellefonte, PA, USA). Calibration curves of SCFAs in concentration between 0.25 and 10 mM were constructed to obtain SCFAs quantification, and 10 mM 2-ethylbutyric acid was used as an internal standard. Results are expressed as mg/g of dry weight of feces.