In specialized dairy systems, there are problems due to the low development of calf rumen function, causing a delay in the beginning of productive life of the replacement animals. The aim of this study was to evaluate the supplementation of functional additives on the development of rumen. A total of 49 one-day-old Holstein calves were randomly assigned to 6 experimental groups: (1) Control (C), (2) oregano essential oil (OEO), (3) native yeast (NY), (4) Combination1 (OEO+Y1), (5) Combination2 (OEO+Y2), (6) Combination3 (OEO+Y3). Whole milk (2.8%CP, 3.2%fat) was offer twice daily until d 90. Calf starter (18%CP, 2.43 ME Mcal/kg DM) was used for all treatments and was available free choice. Milk intake (4.27–4.37L/d), ADFI (463–529g/d), and ADG (568–675g/d) were similar in all groups (P > 0.05). At the end of the trial (112 d), 3 calves per treatment were selected and slaughtered to extract rumen samples and take measurements of ruminal papillae development. The surface area of the papillae, as a function of their length and width, was determined in 9 regions of the rumen: caudal portion of caudal ventral blind sac (A), left side caudal dorsal sac (LB), left side cranial dorsal sac (LC), left side cranial ventral sac (LD), left side ventral portion of caudal ventral blind sac (LE), right side caudal dorsal sac (RB), right side cranial dorsal sac (RC), right side cranial ventral sac (RD), right side ventral portion of caudal ventral blind sac (RE). Data were analyzed as a completely randomized design with a factorial arrangement of treatments (6 × 9) using PROC GLIMMIX. The rumen papillae with greater surface area were observed in the cranial-ventral portions (RD 2.46, LD 1.84 mm²), while the less surface area were found in LC, RC, A (1.14, 1.22, 1.17 mm², respectively). Calves fed with NY treatment had the greatest papillae surface area in all the regions (P < 0.05). The interaction region × treatment was affected due to the supplementation of the additive (P < 0.001), however, no difference were observed in A, LB, RB, RE regions (P > 0.05), whereas in RD calves supplemented with OEO showed the greatest surface papillae area (3.25 mm²). In conclusion, supplementation of native yeasts as a functional additive improves calf rumen development.