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Many feeding strategies have been proposed to mitigate the effects of weaning; one key approach is the inclusion of dietary fiber. Dietary fiber is composed of soluble fiber and insoluble fiber, and its importance lies in its role in improving intestinal physiology.
Objective and methods: The aim of this study was to conduct a physicochemical analysis of milled almond shells at different particle sizes, and to evaluate the effects of including 2.5% almond shells as an insoluble fiber source in weaned piglet diets: finely milled almond shells, geometric mean diameter (GMD): 529 µm; medium milled almond shells, GMD: 912 µm; and coarsely milled almond shells, GMD: 1,525 µm-in comparison with 8% wheat bran. All diets were formulated to be iso-NDF, iso-energetic, and iso-nitrogenous. Outcomes assessed after 14 days post-weaning included growth performance, dry matter digestibility, intestinal morphology, relative gene expression, microbial composition, and volatile fatty acid (VFA) production.
Results: Regarding physical analyses, wheat bran showed higher swelling capacity, cold solubility, and water holding capacity than almond shells. Piglets fed finely milled, medium milled, and coarsely milled almond shells diets showed higher final body weight, average daily gain, and feed intake, along with a higher gain-to-feed ratio compared to those fed wheat bran. Histomorphology analysis revealed increased villus surface area and mucosal thickness in the jejunum and ileum of almond shell-fed piglets. In the colon, coarsely milled almond shell-fed piglets exhibited greater crypt depth than those fed wheat bran. Reduced relative abundance of Proteobacteria was observed in all almond shell groups compared to wheat bran. Coarsely milled almond shells also led to higher total VFA production, butyrate, and propionate concentrations in colonic contents relative to finely milled almond shells, medium milled almond shells, and wheat bran diets.
Conclusion: These findings support the benefits of including 2.5% almond shells in weaned piglet diets, improving performance, intestinal morphology, microbiota composition, and particularly coarse almond shells improved VFA production when compared to wheat bran.
Ruiz E, Martínez-Miró S, Madrid J, Ortega N, Sánchez CJ, Montalbán A, Ayala L, Pallarés FJ, Hernández F. Reducing the weaning impact in piglets with dietary fiber: the role of milled almond shells compared to wheat bran. Journal of Animal Science. 2026; 104: skaf420. https://doi.org/10.1093/jas/skaf420