From gut health to nutrient digestion and metabolism: An integrative biomarker analysis in nursery pigs

This study aimed to explore the relationship between intestinal health biomarkers and nutrient digestion and metabolism in nursery pigs. Thirty-two weaned pigs were individually housed and fed a single experimental diet for 22 days. Feces and urine were collected on days 15 to 21 post-weaning to assess energy and protein digestibility and metabolizability. Blood samples were collected on day 22 to assess intestinal permeability, IgG, and IgA. Fecal samples were collected on the same day to quantify calprotectin, neopterin, lactoferrin, calcium-binding proteins, and fatty acid-binding protein (FABP). All pigs were euthanized on day 22 for intestinal tissue collection to determine villus height, villus width, crypt depth, and villus height-to-crypt depth ratio, thiobarbituric acid reactive substances (TBARS), glutathione S-transferase, protein thiols, resistance to rupture, zonula occludens-1, and occludin. Principal component analysis (PCA), correlation, and classification and regression tree (CART) methods were applied. Fecal calcium-binding proteins and FABP levels were identified in the tree-based models (CART) as key predictors of dry matter digestion. On the other hand, fecal calprotectin and FABP levels were the primary determinants of protein and energy digestibility and metabolizability. Fecal calprotectin levels between 79.4 and 79.6 ng/mL served as the cutoff to distinguish nursery pigs with high and low digestibility in two different CART models. Similarly, the cutoff for FABP levels ranged from 70.5 to 87.4 ng/mL, indicating its role in differentiating groups with high and low efficiency. Our results support the potential of fecal biomarkers as non-invasive indicators of digestibility and metabolism in weaned pigs.