The objective was to investigate the effects of orally dosed lipopolysaccharide (LPS) and Na-butyrate on rumen cell proliferation in Holstein dairy calves. The hypothesis was that LPS and butyrate synergize to promote rumen development. Twenty-two bull calves arrived in one of 2 groups, spaced 2 wk apart. Within each group, calves were assigned to one of 4 treatments: control (CON; n = 5), butyrate (BUTY; n = 5), LPS (n = 6), or LPS plus butyrate (LPSB; n = 6). All treatments were administered orally twice daily and consisted of either: 0.9% saline (CON); 11mM Na-butyrate (BUTY); LPS ranging from 2.5 to 40 μg/kg body weight (BW)^0.75 (LPS), or both butyrate and LPS (LPSB). LPS dosage volume increased across weeks, ranging from 10 to 40 mL per dose. Calves were fed milk replacer (22%CP, 20% fat) and starter (20% CP, 3% fat) twice daily based on metabolic BW. Feed intake, fecal and respiratory scores, and rectal temperature were recorded daily. Calf BW, hip height, blood samples, and rumen content samples were collected weekly. Calves were weaned at 6 wk of age and euthanized at 8 wk of age, whereupon ruminal weights and ruminal samples for papillae area and epithelial thickness were collected. Blood and rumen samples were analyzed for blood metabolites (BHBA and glucose) and VFA concentrations, respectively. Feed intake, health measures, and blood metabolites did not differ by treatment. Calf BW increased by week (P < 0.0001). Irrespective of week, LPS weighed more and had higher ADG than BUTY (P = 0.020). Irrespective of week, withers height was higher in LPS compared with CON (P = 0.006). Rumen pH and rumen VFA concentrations did not differ by treatment but did decrease and increase, respectively, with week in conjunction with increased starter intake. Total empty stomach (P = 0.014) and reticulorumen weights (P = 0.012) were higher in LPSB compared with BUTY. Here, LPS and BUTY appeared to have synergistically affected some, but not all rumen measurements without affecting calf growth, intake, or health. This suggests that frequent oral exposure to LPS may have a direct effect on calf rumen growth.