Seventy-one neonatal Holstein calves (40 female; 31 male) were used in a randomized block design with a 2 × 2 factorial arrangement of treatments to evaluate the effects of milk replacer (MR) feeding management alone or in combination with a multivitamin and electrolyte supplement on growth performance and mitigation of heat stress in southeast Louisiana. Milk replacer treatments consisted of Land O’Lakes Herdmaker Supreme (20% CP, 20% fat; CON) and Land O’Lakes Warm Front (27% CP, 10% fat; WF). Supplemented calves received either 0 or 20 mL of Palamountains Calf Boost (CB) in MR once daily. Calves were offered MR treatments and water and calf starter (20% CP) ad libitum beginning on d 2. All milk replacer was mixed at 15% solids. Calves consuming CON were fed 2.28kg MR twice daily. Calves on WF were fed 2.72kg MR twice daily for the first 3 weeks of life, and 3.86kg twice daily until weaning. Beginning on d 42, MR feeding was reduced to 1 time per day for all treatment groups to decrease MR intake by 50%. On d 49 calves were weaned. Calves remained in their hutches until d 56 to determine immediate post weaning performance. Blood was collected on d 14, 28, 42, and 56 for analysis of plasma urea nitrogen (PUN), glucose, and β-hydroxybutyrate (BHBA), as well as rumen fluid for analysis of volatile fatty acids (VFA) and pH. Data were analyzed using the PROC MIXED procedure in SAS. A main effect of milk replacer composition on PUN was observed, with calves fed WF having greater concentrations (P < 0.05) than CON. Glucose concentrations decreased (P < 0.05) as calves aged. There was no treatment effect (P > 0.05) on plasma BHBA, but concentrations increased (P < 0.05) as calves aged. Likewise, there was no treatment effect (P > 0.1) on rumen acetate, propionate, butyrate, and total VFA concentrations; however, concentrations increased (P < 0.05) as calves aged. No effects of treatment or time were observed (P > 0.05) for rumen pH. These data indicate that milk replacer composition and feeding management and multivitamin mineral supplements do not affect negatively metabolism or rumen development in young dairy calves.