The aim of this trial was to evaluate effects of two medicated feeding strategies versus an alternative one on performances and fecal bacteria diversity in piglets. A total of 144 piglets weaned at 21 days were fed ad libitum with a two-phase diet program supplying 10.8 MJ/kg of net energy (NE) and 1.22% of standardized ileal digestible (SID) lysine (Lys) (days 0-21) and 9.6 MJ/kg of NE and 1.05% of SID Lys (days 21-47). Piglets were divided into 4 experimental groups with different supplementations: a control group (CTL), with no supplementation; an antibiotic group (ATB), with 500 ppm of amoxicillin and 3,200,000 IU/kg of colistin from days 0-21; a zinc oxide group (ZnO), with 2500 ppm of Zn from days 0-21; and a flavor substance (FS) group, with 1000 ppm of a microencapsulated flavor throughout the trial. Piglet growth and feed intake were recorded, and gut microbiota composition was assessed by sequencing the 16S rRNA gene from fecal DNA samples before weaning and at 21 and 47 days post-weaning. Piglets in the ATB group had an improved feed conversion ratio from days 0-21. At day 47, piglets in the FS group weighed more than those in the CTL group. Piglets treated for digestive causes were more common in the CTL and ZnO groups. FS and CTL groups had the highest α-diversity of gut microbiota at days 21 and 47. A strong reduction in α-diversity was observed in the ZnO group at day 21. Maintenance of bacterial diversity may have a positive effect on the health and performance of piglets after weaning.