Probiotic additives are used to prevent diarrhea episodes in weanling dairy calves and to improve animal well-being, growth, and weight gain.In this study, we developed an emulsion that offered protection over time to its four constituent anaerobic probiotic bacteria (Butyrivibrio fibrisolvens B9, Streptococcus bovis C2, Fibrobacter succinogenes Fs, and Ruminococcus flavefaciens Rf ).When it was stored over 6 months at 4ºC, a significant reduction (P ≤ 0.05) of viable cell counts, from 1.95 x 10 9 CFU/mL at time zero to 3.02 × 10 8 CFU/mL at 6 months, was noted; despite this, viable cell counts were never less than 1 × 10 8 CFU/mL; the minimum suggested for probiotic effectiveness.During in vivo trials, weanling dairy calves were given either a no-bacteria control, a freshly prepared, or stored probiotic emulsion.After 2 and 3 months, as compared to control calves, greater weight gains (up to 15.5%), lower weaning time (15 d), and lower frequency of diarrhea (up to 67.7%) were seen in calves given the freshly prepared and stored probiotic emulsions (P ≤ 0.05).The carrier emulsion protected the viability of the cells and thus their efficacy.