Addition of a Bacillus based probiotic to the diet of preruminant calves: Influence on growth, health, and blood parameters

This study evaluated the addition of a Bacillus-based probiotic to milk replacer and starter for preruminant calves. Forty Holstein calves (1 to 4 d old) were housed individually and blocked by sex and date of birth with treatments assigned randomly within blocks. The treatments were pro-biotic (PRO; 10⁹ cfu/d) added to the milk replacer or control (CON) in which there was no additive. All calves received a milk-based milk replacer containing their respective treatment during the initial 14 d on the experiment. On d 15, treatment was maintained but milk replacer was abruptly switched from milk to soy based. All calves remained on the soy-based milk replacer until weaning. Weaning occurred when starter consumption exceeded 1% of body weight for three consecutive d. After 42 d on the study, unweaned calves were reduced to one feeding of milk replacer daily to promote increased starter intake. Weaned calves were maintained on a commercial starter containing probiotic at 10⁶ cfu/g starter (PRO) or starter with no microbial additives (CON) ad libitum through the 56-d experiment. Dry matter intake (sum of the two food sources) was recorded daily and fecal output was scored (fecal scoring: fluidity, 1=normal, 2=soft, 3=runny, 4=watery; Consistency, 1 = normal, 2 = foamy, 3 = mucus, 4 = sticky, 5 = constipated; Odor, 1 = normal, 2 = slightly offensive, 3 = highly offensive). A scour day was recorded if fuidity = 3 or 4, consistency = 3, and odor = 2 or 3. Calves were weighed weekly and measured for hip height, wither height, hip width and heart girth. Blood samples were collected weekly by jugular venapuncture and analyzed for hematocrit, plasma Beta-hydroxybutyrate (BHB), total protein (TPROT), and Immunoglobulin G1 (IgG1) concentrations. Treatment did not affect d to weaning, incidence or duration of scouring, or growth performance (P≥0.27). Hematocrit and plasma TPROT and IgG1 concentrations changed (P≤0.002) over time but were unaffected by treatment (P≥0.31). Plasma BHB concentrations increased (P<0.0001) over time and tended (P=0.12) to be greater for PRO calves. However, lack of difference in growth performance and health characteristics may indicate that calves housed indoors in a temperature controlled environment with little added stressor may not benefit from probiotic feeding.