Almond shell as an insoluble fibre source in laying pullets: influence of inclusion level and particle size on performance and intestinal health

Dietary fibre (DF) is increasingly recognised for its role in poultry nutrition, particularly in supporting gut health. Almond shells (AS), rich in insoluble fibre (IF), represent a potential DF source. This study assessed the effects of fine (FAS) and coarse (CAS) AS included at 1% and 2% (FAS1, FAS2, CAS1, CAS2) compared with a control diet (NC) without supplemental IF on growth performance, dry matter digestibility, organ development, intestinal morphology, gene expression, caecal microbiota, and volatile fatty acids (VFA) in 6-week-old pullets over 28 days. AS inclusion did not influence productive parameters (P > 0.05). However, diets with 2% FAS, 1% CAS, and 2% CAS improved dry matter digestibility versus NC (P P P P P > 0.05). In conclusion, AS inclusion as an IF source was associated with improved dry matter digestibility, increased relative weights of the proventriculus and gizzard, and enhanced intestinal morphology, particularly at 2% inclusion and in coarse particle form. Although, no effects were detected on growth performance, microbiota, or VFA profiles.