Probiotics are used to control or maintain a constant state of intestinal bacteria. When the bacterial populations are altered by stress or antibiotic therapy, animal health and performance may decline. This experiment was designed to study the effects of feeding a Probiotic (Saccharomyces cerevisiae CNCM I-1079) on growth and health of neonatal Holstein calves. Forty –five neonatal Holstein calves were selected from one dairy farm of Mashhad suburb. After birth,calves were randomly assigned to three groups.Calves in group I (control group) received no probiotic. Calves in group II (experiment I group) were given probiotic at 1gr/day with colostrum and then with milk during the first 2 weeks of life. Calves in group III (experiment II group) were given probiotic at 1gr/day with colostrum and then with milk during the first 3 weeks of life.At the third week, milk was replaced with milk replacer.The body weight and skeletal growth (Heart girth,body length and weithers height) were measured at birth and repeated every week until 5 weeks of age.Blood samples were collected via jugular vein puncture at the time of weighing and analyzed for hematological indices ,plasma total protein concentration and fibrinogen concentration.Fecal scores(fluidity) were monitored and evaluated. All calves were monitored for health status and probable health problems daily. Data were analyzed by using ANOVA, Kruskal-Walis and Chi-square procedure with SPSS 13.There was not significant differences between groups for hematological indices , plasma total protein concentration and plasma fibrinogen concentration, skeletal growth averege daily gain, the incidence of neonatal diarrhea and the days of the treatment; however,fecal scores at third weeks of age between groups I(1/8±0/26) and III(1/07 ±0/07) was significantly different.(P<0.05 ). The results of this study indicated that under the circumstance of this investigation, Probiotic (Saccharomyces cerevisiae CNCM I-1079) was not effective in improving calf performance and health but under nutritional stress condition was effective in maintaining fecal score

Keywords