Field Pea Variants affect Nutrient Digestibility and Gut Microbiome in Pigs

The digestibility of nutrients in different field pea variants in pigs can vary due to characteristics such as anti-nutritional factors. Undigested nutrients can be fermented in the hindgut, and their amount and composition likely affect microbial composition. This study compared a spring field pea variant (SP) with two winter field pea variants (WP1, WP2) with higher trypsin inhibitor activity and a tannic spring forage pea variant (SFP) in terms of nutrient digestibility and effects on the gut microbiome in growing pigs. Four diets containing 40% of one of the four field pea variants were formulated and randomly assigned to 8 ileally cannulated barrows according to a 4 × 4 double Latin square design with the blocking factors animal and period. The experiment consisted of 4 periods, each lasting 11 days. Ileal digesta and feces were collected for 2 days each to determine nutrient digestibility. On the last day of every period, ileal digesta and feces were sampled and analyzed for digestive enzyme activity, metagenomics, metaproteomics, and metabolomics. The data was integrated using DIABLO. The winter field pea variants decreased the prececal digestibility of 16 amino acids (P ≤ 0.032) and increased the activity of carboxypeptidase A (P = 0.002). Pigs fed the SFP showed decreased hindgut disappearance of total dietary fiber (P < 0.001) and concentrations of acetate, propionate, and butyrate in the feces (P ≤ 0.026). More differentially abundant taxa in metagenomic and metaproteomic data were detected in the feces than in ileal digesta among field pea variants. The SFP increased the abundance of host proteins related to innate immune response in ileal digesta and feces (adjusted P ≤ 0.047). Integration of the acquired data layers revealed a negative association of ileal amino acid concentrations with the abundance of Prevotella and proteins related to starch degradation and propionate production in the ileal digesta for winter field pea variants. For SFP, reduced hindgut disappearance of total dietary fiber was associated with a reduction of proteins from Ruminococcus. In conclusion, field pea variants can affect the ileal and fecal microbiome in pigs, potentially due to anti-nutritional factors that either indirectly influence the microbiome by reducing nutrient digestibility or directly affect individual microbial taxa.