Probiotics may prevent or reduce illness occurrence. The objective of this study was to observe the effects of a probiotic (Protect, Provita Animal Health, Omagh, Northern Ireland) on calf diarrhea incidence and average daily gain. This study was conducted at the University of Kentucky Coldstream Dairy during the winter of 2014 and 2015. All female and male Holstein calves were enrolled at birth, fed a colostrum replacer (Bovine IgG Colostrum Replacer, Land O’Lakes, Shoreview, MN), and did not receive any vaccinations. Calves were housed in individual sawdust-bedded hutches with ad libitum access to water and 18% CP starter until weaning at 8 weeks of age. Calves were fed a 20:20 non-medicated milk replacer (total 0.71 kg powder daily) twice daily. Calves were randomly assigned to one of 3 treatments: 10 g liquid oral probiotics at birth (O, n = 10), 10 g liquid oral probiotics at birth plus 1 g powder probiotic once daily incorporated in morning milk from d 2 to 14 (O+P, n = 9), and a negative control (CON, n = 9). Calves were weighed once weekly using a scale (Cardinal Digital HSDC Series, Cardinal Scale Mfg. Co, Webb City, MO). Feces were scored once weekly, where 1 represented firm feces which settled once hitting the ground, 2 feces that did not hold form well, 3 feces that readily spread, and 4 feces that was liquid and splattered (Larson et al., 1977). A fecal score of 4 indicated diarrhea. The GLM and FREQ procedures of SAS Version 9.3 (SAS Institute Inc., Cary, NC) were used to analyze data. The incidence of an episode of diarrhea was 80% for O, 75% for O+P, and 88% for CON (P = 0.79). Mean fecal scores from birth to weaning were 2.18 ± 0.55 for O, 2.18 ± 0.35 for O+P, and 2.28 ± 0.52 for CON (P = 0.73). Calves were confirmed with Rotavirus and Coronavirus through PCR in all treatment groups. Average daily gain during the study was 0.47 ± 0.10 kg/d for O, 0.52 ± 0.10 kg/d for O+P, and 0.56 ± 0.10 kg/d for CON (P = 0.42). No significant differences were observed among treatments for average daily gain, fecal score, or incidence of calf diarrhea.