β-Mannans are strongly anti-nutritive polysaccharide fibres found in most vegetable feed ingredients. The objective of the study was to compare piglet performance and antibiotic use between a Control group, fed a conventional 2-phase diet, and an Enzyme treated group, fed an adapted 2-phase diet including a β-mannanase enzyme (Hemicell™ HT; Elanco). A seven-week feeding trial was conducted with 320 pigs in two rotations of 160 piglets in 20 replicate pens of 8 pigs. Two different 3-phase diets were compared: a standard 3-phase control diet and an adapted 3-phase diet including a β-mannanase enzyme included at 300 g/tonne. The following adaptation were made: Phase-1 (weeks 1–3): 0.15% potato protein concentrate and 2.00% Danex [extruded soybean meal (SBM)], was replaced with SBM 48%, Phase-2 (weeks 4–7): β-mannanase was formulated to replace 63 kcal/kg NE. Standard piglet performance parameters (ADWG, ADFI, FCR) and antibiotic use were recorded. All data analyses were performed using R version 3.6.3 (R Core Team, 2020). All tests were performed at the 5% level of significance. When multiple testing was involved, the nominal 5% Familywise Error Rate (FWER) was used. Throughout the trial and within each phase, ADWG, ADFI and FCR were not significantly different (P > 0.05) between Control and Enzyme group. No mortality occurred and no antimicrobials were used in either of the treatment groups.