Reduction of amylose–amylopectin ratio in low-protein diets: impacts on growth performance and intestinal health in weaned pigs

Improving the synchrony between amino acids (AAs) and glucose appearance in the blood can support the growth performance of weaned pigs fed a low crude protein (CP) diet. This can be achieved using a diet with a low amylose-to-amylopectin ratio (AM/AP). The aim of this experiment was to evaluate whether reducing the AM/AP by using a corn variety characterized by a high amylopectin content, in the weaning diet can sustain growth performance and improve the intestinal health of pigs fed a low-CP diet. At weaning (25 ± 2 d), 90 pigs were assigned to 3 treatment groups: 1) control group (CTR), fed a standard diet with a medium-high CP content and high AM/AP (days 0 to 13: 18.0% CP, 0.13 AM/ AP; days 14 to 27: 16.6% CP, 0.30 AM/AP; days 28 to 49: 16.7% CP, 0.15 AM/AP); 2) a group fed a low-CP diet with a high AM/AP (LP) (days 0 to 13: 16.0% CP, 0.17 AM/AP; days 13 to 27: 14.7% CP, 0.17 AM/AP; days 28 to 49: 14.5% CP, 0.25 AM/AP); 3) a group fed a low CP and a low AM/AP diet (LPLA) (days 0 to 13: 16.0% CP, 0.09 AM/AP; days 14 to 27: 14.7% CP, 0.05 AM/AP; days 28 to 49: 14.5% CP, 0.09 AM/AP). Pigs were weighted weakly until day 49. Fecal samples were collected on days 10 and 42 (12 samples/group/timepoint) for ammonia and calprotectin content and microbiota profile characterization. Until day 28, body weight (BW) of pigs from CTR was not different from pigs of the LPLA group, whereas it was higher from pigs of the LP group (P < 0.05). Thereafter, CTR group had greater BW compared with LP and LPLA groups for all the other timepoints considered (P < 0.05). From days 0 to 7 LPLA group had a lower incidence of diarrhea than the LP group (P = 0.04). On day 10, LPLA group had a greater alpha diversity (Shannon and InvSimpson indices), than the CTR (P = 0.03) and LP (P = 0.04) groups. On day 42, LPLA group had significantly greater InvSimpson diversity than LP group (P = 0.028). On day 10, LP group was characterized by greater abundance of Lactobacillus (LDA score = 5.15, P = 0.02), Clostridium-sensu-stricto-1 (LDA score = 4.90, P = 0.02) and Oscillospiraceae NK4A214-group (LDA score = 4.87, P = 0.004), whereas LPLA group was characterized by greater abundance of Prevotella (LDA score = 5.04, P = 0.003) and Agathobacter (LDA score = 4.77, P = 0.05). In conclusion, while reducing CP levels may negatively impact growth performance, when combined with higher amylopectin levels, it can reduce the incidence of diarrhea and increase fecal microbial diversity.