Immunisation against lactic acidosis in cattle

The present study was designed to investigate the efficacy of control of la ctic acidosis by immunisation against lactic acid-producing bacteria, Strep tococcus bovis and Lactobacillus. Ten steers were allocated to two treatmen t groups. One group was immunised with a vaccine containing S. bovis (strai n Sb-5) and Lactobacillus (LB-27) cells, and the other was a non-immunised control group. The vaccine, using Freund's complete adjuvant for primary im munisation and Freund's incomplete adjuvant for boosters, was administered intramuscularly. After primary immunisation, boosters were given at 2 to 4 week intervals. Both anti-S bovis and anti-Lactobacillus IgG levels in sali va increased significantly (P < 0.01) after the Ist booster which were lowe r (P < 0.05) than the IgG levels after the 2nd and 3rd boosters. but were n ot significantly different (P > 0.05) from the IgG levels prior to a grain challenge (after the 4th booster). There were positive correlations between the anti-S.bovis and anti-lactobacillus IgG in serum and saliva. Compared with the control group, steers in the immunised group had higher (P < 0.05) feed intakes, lower (P < 0.05) rumen concentrations of lactate and lower n umbers of S. bovis and Lactobacillus. Three of the control animals were wit hdrawn from the grain challenge due to their rumen pH persisting below 5.2, while only one animal in the immunised group was withdrawn. These results suggest that the risk of lactic acidosis can be reduced by immunisation aga inst S. bovis and Lactobacillus.