Evaluation of Mycoplasma hyopneumoniae inactivated vaccine in pigs under field conditions

An inactivated vaccine prepared from broth culture supernatant of Mycoplasm a hyopneumoniae with an aluminum adjuvant was evaluated in three herds (her d A: specific pathogen-free herd, herd B: high health status herd with no c linical signs of respiratory infection, herd C: low health status herd with serious epidemiological and economical problems). A total of 212 pigs from the three herds were divided into two groups. One group was injected twice with the vaccine at 4-week intervals and the other was a control group. No adverse reactions were noted following the vaccinations either systematica lly or locally in any of the vaccinated pigs from any of the herds. In herd A, the vaccination provided antibody response within 4 weeks after the sec ond vaccination and antibody responses continued for more than 12 weeks. In herds B and C, the number of pigs with lung lesions, mean percentage of lu ng lesions, and the numbers of M. hyopneumoniae recovered from pigs at slau ghter in the vaccinated group were significantly (P<0.05) reduced compared to the control group. Furthermore, vaccination resulted in improved average daily weight gain (ADG), improved feed conversion ratio (FCR), and improve d days to market weight in herd C, whereas no difference in growth performa nce was shown in herd B. It is suggested that the inactivated vaccine prepa red from broth culture supernatant of M. hyopneumoniae is effective in redu cing clinical signs and lung lesions. Also, vaccination resulted in improve d growth performance in herds where clinical signs and economic losses were significant.