Reducing the weaning impact in piglets with dietary fiber: the role of milled almond shells compared to wheat bran

Abstract

Many feeding strategies have been proposed to mitigate the effects of weaning; one key approach is the inclusion of dietary fiber (DF). Dietary fiber is composed of soluble fiber (SF) and insoluble fiber (IF), and its importance lies in its role in improving intestinal physiology. The aim of the present study was to conduct a physicochemical analysis of milled almond shells (AS) at different particle sizes, and to evaluate the effects of including 2.5% AS as a IF source in weaned piglet diets—[finely milled AS (FAS), geometric mean diameter (GMD): 529µm], MAS (medium milled AS, GMD: 912µm), and [coarsely milled AS (CAS), GMD: 1,525µm]—in comparison with 8% wheat bran (WB). All diets were formulated to be iso-NDF, iso-energetic, and iso-nitrogenous. Outcomes assessed after 14d post-weaning included growth performance, dry matter digestibility, intestinal morphology, relative gene expression, microbial composition, and volatile fatty acid (VFA) production. Regarding physical analyses, wheat bran showed higher swelling capacity, cold solubility, and water holding capacity than AS (P<0.05). Piglets fed FAS, MAS, and CAS diets showed higher final body weight, average daily gain, and feed intake, along with a higher gain-to-feed ratio compared to those fed WB (P<0.05). Histomorphology analysis revealed increased villus surface area and mucosal thickness (P<0.05) in the jejunum and ileum of AS-fed piglets. In the colon, CAS-fed piglets exhibited greater crypt depth than those fed WB (P<0.05). Reduced relative abundance of Proteobacteria was observed in all AS groups compared to WB. Coarsely milled AS also led to higher total VFA production, butyrate, and propionate concentrations in colonic contents relative to FAS, MAS, and WB diets (P<0.05). These findings support the benefits of including 2.5% AS in weaned piglet diets, improving performance, intestinal morphology, microbiota composition, and particularly coarse AS improved VFA production when compared to wheat bran.