Dietary fiber supplementation during the last 50 days of gestation improves the farrowing performance of gilts by modulating insulin sensitivity, gut microbiota, and placental function.

Our previous study found dietary konjac flour (KF) supplementation could improve insulin sensitivity and reproductive performance of sows, but its high price limits its application in actual production. This study aimed to investigate the effects of supplementation of a cheaper combined dietary fiber (CDF, using bamboo shoots fiber and alginate fiber to partially replace KF) from the last 50 days of gestation to parturition on farrowing performance, insulin sensitivity, gut microbiota, and placental function of gilts. Specifically, a total of 135 pregnant gilts with a similar farrowing time were blocked by backfat thickness and body weight on day 65 of gestation (G65d) and assigned to 1 of the 3 dietary treatment groups (n = 45 per group): basal diet (CON), basal diet supplemented with 2% KF or 2% CDF (CDF containing 15% KF, 60% bamboo shoots fiber, and 25% alginate fiber), respectively. The litter performance, insulin sensitivity and glucose tolerance parameters, placental vessel density, and short-chain fatty acids (SCFAs) levels in feces were assessed. The gut microbiota population in gilts during gestation was also assessed by 16S rDNA gene sequencing. Compared with CON, both KF and CDF treatments not only increased the piglet birth weight (P < 0.05) and piglet vitality (P < 0.01) but also decreased the proportion of piglets with birth weight ≤ 1.2 kg (P < 0.01) and increased the proportion of piglets with birth weight ≥ 1.5 kg (P < 0.01). In addition, KF or CDF supplementation reduced fasting blood insulin level (P < 0.05), homeostasis model assessment-insulin resistance (P < 0.05), serum hemoglobin A1c (P < 0.05), and the level of advanced glycation end products (P < 0.05) at G110d, and increased the placental vascular density (P < 0.05) at farrowing. Meanwhile, KF or CDF supplementation increased microbial diversity (P < 0.05) and SCFAs levels (P < 0.05) in feces at G110d. Notably, the production cost per live-born piglet was lower in CDF group (¥ 36.1) than KF group (¥ 41.3). Overall, KF or CDF supplementation from G65d to farrowing could improve the farrowing performance of gilts possibly by improving insulin sensitivity, regulating gut microbiota and metabolites, and increasing placental vascular density, with higher economic benefits and a similar effect for CDF vs. KF, suggesting the potential of CDF as a cheaper alternative to KF in actual production.