SUMMARY Twenty crossbred Holstein x Jersey calves, distributed in a completely randomized block design were used to evaluate the effect of probiotic of ruminal bacteria supply on performance and blood parameters of dairy calves in early weaning system. Animals were submitted to control treatment or supplementation of 2g/ day of probiotic via milk replacer. The calves received 6 liters of milk replacer per day divided in two daily meals and were gradually early weaned at the 6th week of age, however, all data were collected until 10th week of age. Starter feed intake and fecal score were registered daily. Weekly, body weight, and body measures like, height withers, hip width and heart girth were taken. Blood samples were taken at the 2nd, 4th, 6th, 8th and 10th week, two hours after the morning feeding, to determine plasma concentrations of glucose, total protein, albumin, β-hydroxybutyrate and cortisol. Probiotic supplementation didn´t affect starter feed intake, daily weight gain, weight or body measurements. The probiotic supply also had no effect on fecal scores between treatments. Blood parameters were not affect by probiotic supplementation. The probiotic of ruminal bacteria supply present no benefits on the performance or metabolism of dairy calves in early weaning system.

SUMMARY Twenty crossbred Holstein x Jersey calves, distributed in a completely randomized block design were used to evaluate the effect of probiotic of ruminal bacteria supply on performance and blood parameters of dairy calves in early weaning system. Animals were submitted to control treatment or supplementation of 2g/ day of probiotic via milk replacer. The calves received 6 liters of milk replacer per day divided in two daily meals and were gradually early weaned at the 6th week of age, however, all data were collected until 10th week of age. Starter feed intake and fecal score were registered daily. Weekly, body weight, and body measures like, height withers, hip width and heart girth were taken. Blood samples were taken at the 2nd, 4th, 6th, 8th and 10th week, two hours after the morning feeding, to determine plasma concentrations of glucose, total protein, albumin, β-hydroxybutyrate and cortisol. Probiotic supplementation didn´t affect starter feed intake, daily weight gain, weight or body measurements. The probiotic supply also had no effect on fecal scores between treatments. Blood parameters were not affect by probiotic supplementation. The probiotic of ruminal bacteria supply present no benefits on the performance or metabolism of dairy calves in early weaning system.