We compared the prevalence of salmonella in faecal samples from
finishing pigs and in feed
samples from swine herds in North Carolina, USA. Farms were either
finishing sites using all-in/all-out management of buildings in
multiple-site systems (14 farms) or farrow-to-finish
systems using continuous flow management of finishing barns (15
farms). The two groups of
herds differed with respect to several management variables. Salmonella
isolated from 565
of 2288 (24·6%) faecal samples and from at least 1 faecal sample
on 24 of 29 (83%) farms.
Predominant serotypes were S. derby, S. typhimurium
(including copenhagen), S. heidelberg, S.
worthington and S. mbandaka. Fewer farrow-to-finish farms
were detected as positive compared
with all-in/all-out farms. Prevalence was lower for pigs raised on
slotted floors compared with
all other floor types, and was highest for pigs raised on dirt
lots. Modern methods of raising
pigs in multiple-site production systems, using all-in/all-out
management of finishing pigs,
appear to have no benefit in reducing the prevalence of salmonella
compared with conventional farrow-to-finish systems.