Methods to improve calf growth and health, with reduced antibiotics use are essential for a successful and profitable dairy. This study evaluated the performance and fecal pH of dairy calves receiving milk replacer supplemented or not with probiotic. Twenty-four newborn Holstein male calves were utilized in a randomized blocks experimental design, and distributed into 2 treatments: Control: no probiotic supplementation; Supplementation of 2g/d of a Bacillus subtilis (1.6 × 10⁹ cfu) and Bacillus licheniformis (1.6 × 10⁹ cfu) containing probiotic (Bioplus, Chr. Hansen), via milk replacer. Calves were individually housed, with free access to water and starter (20% CP and 80% TDN), and received 4L/d of milk replacer (FeedTech, DeLaval, 21.6:15.5, 12.5% solids) until the eighth week of life, when weaned. Feed intake was monitored daily; while body weight, height withers, heart girth, hip width and fecal pH were weekly measured. Data were analyzed as repeated measures, considering treatment, age, and their interaction effects. There were no probiotic supplementation effects on growth and starter intake (P > 0.05). As animals were growing, all parameters were significantly affected by age (P > 0.05); however, there were no treatment and age interaction effect (P > 0.05). On the other hand, probiotic supplementation tended to reduce fecal pH, suggesting a change in intestine microorganisms and probably a reduction on pathogens growth. Table 1. Performance of calves receiving milk replacer supplemented with probiotics

Iten	Treatment		SEM	P <1
Control	Probiotic	T	A	T × A
Initial BW, kg	36.54	35.47	0.82	0.48	—	—
Weaning BW, kg	57.22	56.64	1.99	0.89	—	—
ADG, kg	0.39	0.44	0.03	0.49	0.0001	0.81
Average starter intake, g/d	372.8	362.0	28.6	0.89	0.0001	0.72
Withers height, cm	78.8	79.2	0.2	0.68	0.0001	0.98
Heart girth, cm	81.1	80.7	0.4	0.71	0.0001	0.39
Hip width, cm	22.0	22.1	0.09	0.68	0.0001	0.86
Fecal pH	6.75	6.79	0.04	0.07	0.001	0.02

¹T = treatment effect; A = age effect; T × A = treatment and age interaction effect.