This study investigated the effects of dietary fibre type, particle size, and weaning age on colonic morphology, mucin distribution, and immune function in piglets. Ninety-four piglets were assigned to groups based on weaning age (28 ± 2 days, conventional weaning, CW; 42 ± 2 days, late weaning, LW) and fed diets with hay or sugar beet pulp (SBP, fine or coarse particles). After two weeks, tissue samples were collected. SBP enhanced the expression of IL-10 (P = 0.001) and GPR43 mRNA (P = 0.029), while it enhanced mucin presence in LW piglets (P < 0.01). In LW piglets, coarse particles increased crypt area (P = 0.012), and fine particles increased immune cell infiltration. Weaning age also affected crypt morphology and goblet cell numbers, with LW piglets showing deeper crypts (P < 0.001). Results suggest that fibre type, particle size, and weaning age significantly influence gut health and immunity.
