Comparative Effects of Processed Soybean Protein Sources on Growth, Serum Immune and Endocrine Profiles, and Colonic Microbiota in Weaned Piglets

Abstract

Simple Summary Conventional soybean meal is the principal plant protein source in piglet diets, but its antinutritional and antigenic components may impair intestinal function in newly weaned piglets. These components can contribute to reduced feed intake, diarrhea, and impaired growth during the nursery phase. Although extrusion, fermentation, and enzymatic hydrolysis are widely used to improve soybean nutritional quality, most studies have evaluated only a limited set of outcomes. This 28-day study compared five commercially available soybean protein ingredients using growth, feed preference, protein digestibility, serum biomarkers, and colonic microbiota. Hydrolyzed soybean protein contained no detectable glycinin and the lowest measured concentration of major antigenic proteins, showed the highest crude protein digestibility, and was associated with higher serum IgA, GH, and IGF-1 concentrations, lower TNF-α concentrations, and greater weight gain. Fermented and rapidly expanded soybean meals produced more modest responses. Feed preference did not differ among treatments. Alpha diversity also did not differ significantly, whereas the relative abundance of Lactobacillus was higher in the hydrolyzed and fermented soybean protein groups in the descriptive genus-level analysis. These results provide comparative evidence to guide the selection of processed soybean proteins for nursery pig diets.