Effects of Gal-E-mutant of Salmonella typhimurium on experimental salmonellosis in chickens.

Compared with unvaccinated challenged birds, day-old chicks vaccinated orally with live Salmonella typhimurium galactose epimerase mutant (G30D) and challenged orally after 14 days with a field strain of S. typhimurium had statistically significant reductions in fecal shedding (P less than 0.01), in salmonella carrier status at slaughter (P less than 0.05), in salmonella in the broiler-house environment (P less than 0.005), and in serological response in the fourth week after challenge (P less than 0.005). The vaccine did not elicit a serological response as measured by plate, microagglutination, and microantiglobulin tests. The vaccine had a significant depression on live-weight gain which was not apparent after 6 weeks. The vaccine did not significantly reduce live weight at 8 weeks below that of unvaccinated control birds. The field strain produced an 8% reduction in live weight at 8 weeks below that of controls. The potential role of vaccines in salmonella control, and economic losses due to salmonellosis, are discussed.