Heifers injected with 10(8) (n = 40), 10(9) (n = 39), or 10(10) (n =39) colony-forming units of Brucella abortus strain 19 were conjunctivally exposed to 10(7) colony-forming units of strain 2308 during gestation. At parturition, milk from each quarter of the udder, a piece of placenta, and 2 swab specimens of the uterus from the dam plus a swab specimen of the rectum from each calf were cultured for Brucella. If the calf was dead or died, additional specimens of lung, stomach contents, and a mediastinal lymph node also were cultured. Days in gestation was determined for each heifer, using data from rectal palpation after breeding and crown-rump length and weight of calf at parturition, with the median value used for data analysis. In each vaccine dosage group, the proportion (%) of heifers developing brucellosis increased as days in gestation at exposure increased. Strain 2308 was isolated from 3 (11%) of 26, 16 (25%) of 64, and 18 (64%) of 28 heifers that were grouped as less than 121, 121 to 150, and greater than 150 days in gestation at time of exposure, respectively. Thirty-two (86%) of the 37 infected heifers were less than 260 days in gestation at parturition, and calves were premature. Heifers with premature calves were more likely to be infected, and tissues were more likely to yield multiple isolations of strain 2308, regardless of days in gestation at exposure or of days after exposure to parturition. Days after exposure to premature parturition of infected heifers ranged from 35 to 110.

Neutralizing and nonneutralizing antibodies to bovine viral diarrhea (BVD) virus were detected in 3 cows persistently infected with noncytopathic BVD virus after vaccination with modified-live cytopathic BVD virus. Neutralizing antibodies detected in serum samples from each persistently infected cow at 3 weeks after vaccination were highly specific for certain isolates of cytopathic BVD virus and reacted only with a viral protein with a molecular weight of 53,000. Neutralizing antibodies to 1 of 3 isolates of noncytopathic BVD virus were detected in a serum sample obtained at 12 weeks after vaccination from 1 of 3 persistently infected cows. Nonneutralizing antibodies were detected in all cows at 7 to 12 weeks after vaccination.The nonneutralizing antibodies were less specific for isolates of BVD virus and reacted with viral proteins with molecular weights of 115,000, 80,000, 53,000, and 47,000.

Genetically altered stable nonreverting aromatic-dependent (aro-) Salmonella dublin, strain SL5631, was administered orally to healthy colostrum-fed calves as vaccine. Twenty-six calves were allotted to 4 groups. There were 2 experiments, each with a vaccinated and nonvaccinated control group. Skin testing with 0.1 ml of sonicated S. dublin was performed 3 days prior to challenge exposure. The IgG and IgM titers to S. dublin lipopolysaccharide (LPS) antigen were determined by ELISA on sera before initial vaccination and at 1.5 to 2 weeks after each vaccination. In experiment 1, six calves received a dose of 1.7 X 10(10) colony-forming units (CFU) of aro(-) S. dublin SL5631 orally at 2 and 4 weeks of age. After the first vaccination, 2 of 6 calves developed fever, but all 6 calves continued to have normal appetite and mental attitude. Adverse changes were not observed after the second vaccination. At the time of challenge exposure at 6 weeks of age, all 12 calves were seronegative for IgG and IgM LPS-specific antibodies, and the difference in percentage increase in skin test reaction at 48 hours was not significant. At 6 weeks of age, the 6 vaccinates and 6 controls were orally challenge-exposed with 1.5 X 10(11) CFU of virulent S. dublin T2340. Protection from challenge was not evident, as 3 of 6 controls and 5 of 6 vaccinates died after challenge exposure. In experiment 2, eight calves received a dose of 5 X 10(11) CFU of aro(-)S dublin SL5631 orally at 2, 3.5, and 5 weeks of age. The vaccine dose and volume (300 ml) were 30 times that of experiment 1. After each vaccination, some calves (7, 6, and 2 calves for first, second, and third doses, respectively) developed fever, but all calves continued to have normal appetite and attitude. At 7 weeks of age, the 8 vaccinates and 6 controls were orally challenge-exposed with 1.5 X 10(11) CFU of virulent S. dublin T2340 (same dose as experiment 1).

Swine herds suspected to be infected with Leptospira interrogans serovar bratislava were vaccinated with bacterins containing 5 or 6 leptospiral serovars in which serovar bratislava was the unique component. The principal diagnostic feature indicating an infection by this organism was demonstration of antibody against serovar bratislava in sera from stillborn pigs. For 1 breeding cycle after vaccination of herds on 3 farms, 255 of 266 (95.9%) sows and gilts given the 6-serovar bacterin farrowed. In contrast, 233 of 311 (74.9%) sows and gilts given the 5-serovar bacterin farrowed. These results, as evaluated by analysis of variance techniques, showed a significant improvement (P less than 0.01) in reproductive performance for groups vaccinated against serovar bratislava.