IMPROVED PERFORMANCE OF A LARGE PIG COMPLEX AFTER SEQUENTIAL NURSERY DEPOPULATION

An attempt was made to compare the productivity and financial benefits of nursery depopulation on five large pig farms which were all part o f one complex, Each farm had been experiencing poor post weaning perfo rmance for 12 months, and had previously been infected with porcine re productive and respiratory syndrome virus (PRRSV), A plan to depopulat e each nursery sequentially was established, and the pigs were moved t o fattening facilities on one of the farms (farm 3) where space was av ailable, Over a four week period, the nurseries of farms 1, 2, 4 and 5 were emptied, cleaned and disinfected, and any changes in nursery per formance, mortality and the seroprevalence of antibodies to PRRSV Were then assessed for one year, The financial benefit to the entire farm complex was analysed by using partial budget methods, During the year a net benefit of $1,708,431 was assessed to the farm complex owing to the increased numbers of marketable pigs and the reduced antibiotic co sts, There were highly significant improvements in nursery growth rate and decreases in mortality on farms 1, 2, 4 and 5, and antibodies to PRRSV were detected on farms 3 and 4 but not on farms 1, 2 and 5, The inability to empty the farm 3 fattening facility, which housed the pig s from the other sites, may have led to the maintenance of its PRRSV p ositive status and could have served as the source of virus for farm 4 .