Different sources of resistant starch in vitro show contrasting fermentation and SCFA profiles

Resistant starch (RS) is well known to be fermented in the caecum and the colon of animals, increasing the production of short-chain fatty acids (SCFA), especially butyrate. The latter is health-promoting, exhibiting anti-inflammatory effects on the gut and hence it has been postulated that dietary strategies should aim for an increased intestinal butyrate production in pig production. In this study, five different purified sources of RS (high-amylose maize, potato and pea starches) have been tested in vitro for their fermentation kinetics and SCFA profiles as a preliminary step to include one of these substrates in the diet of sows to modulate intestinal microbiota and fermentation patterns. Briefly, after an in vitro hydrolysis with porcine pepsin and pancreatin, undigested residues recovered by dialysis (1,000 kD) were fermented in vitro for 72 hours in a gas test using sows faeces as microbial inoculum. Six vials per RS source were fermented, 3 were used for determination of SCFA profiles at five consecutive time-points and 3 for the fermentation kinetics based on the monitoring of gas volume at regular intervals. SCFA production and profile was measured by high performance liquid chromatography, while fermentation kinetics was mathematically modelled to allow proper comparison between RS sources. All statistical analyses were performed with the MIXED procedure of SAS and repeated measurements for SCFA. All investigated parameters were influenced (p<0.05) by the RS source. Pea starch showed the highest butyrate level at each time point (>15% of total SCFA from 12 hours after the beginning of the fermentation onwards) and exhibited an extensive and rapid fermentation (highest final gas volume (A) and gas production rate and lowest time to reach A/2) while high amylose maize produced the lowest butyrate proportion (<6% of the total SCFA) during the slowest and lowest fermentation. Therefore, pea starch appears to be the most promising to be used in pig nutrition to modulate intestinal fermentation.