Observations on the distribution of Salmonella on pig multiplier breeding farms

Abstract

Centralisation of the structure of p1g production in the UK has resulted in the development of large integrated compames which supply finishing p1gs as well as centralised services such as compound feed , transport and veterinary serv1ces to the whole company. Typ1cally the integration will comprise an mdoor multiplier farm wh1ch supplies gilts, and other boars, to a range of large outdoor commerc1al breeding farms. Usually artificial insemination IS used on the multiplier farm rather than natural service. Each commercial breeding farm then supplies weaned pigs e1ther to a range of nursery farms or d1rect to fimsh1ng farms. It IS therefore possible to dissem1nate Salmonella to tens or hundreds of other farms if the multiplier herd is 1nfected. Longitudinal studies were carried out on the mult1plier farms for two large companies and a single investigative visit was made to the multiplier farm from a third company. On one of the farms (X) Salmonella Typhimurium and other serovars were widespread in all age groups of pigs and environmental samples. There was a susta1ned reduction in S. Typh1murium after ongoing tetracycline medication for sub-fertility was removed but the improvement for other serotypes was transient. On the second farm (Y) S. Typhimurium was intermittently detected, aga1nst a background of S. Panama. S.Typhimurium DT1 04b and S Derby were found m batches of new replacement gilts, originat1ng from a primary breed1ng company, which had JUSt been delivered to this farm. On the third farm (Z) S. Ohio was predominant, although S. Derby was present in post weaning accommodation for gilts and S. Typh1munum was detected in several groups. It was necessary to sample 1nd1v1dual pens to detect S. Typhimurium on the site because of mask1ng by the other serovars m pooled samples. All three of the compames had a high prevalence in their commercial breeding and finishing herds of the same Salmonella serovars found on the respective multiplier farms.