RISK FACTORS FOR POST WEANING DIARRHOEA IN SWEDISH PIG HERDS

摘要

Sweden has a ban on growth promoters since 1986. Due to consumers criticism the farmers took the initiative in creating this ban. The farmers were unprepared for the ban and the weaning feed and the production systems were not suitable for newly weaned pigs. The effects of the ban were increased post-weaning mortality, higher age at 25 kg and an increased number of antibiotic treatments (3). In 1992 the Swedish Board of Agriculture permitted the use of zinc oxide (2000 ppm Zn) as a feed additive to be used until two weeks after weaning. Zinc in this dose has a prophylactic effect against post-weaning diarrhoea (PWD) similar to that of 160 ppm olaquindox (2). Due to expected toxic effects of zinc on agricultural soils and due to criticism from the EU-commission, zinc oxide in high doses was banned as feed additive in 1998. It can nowadays only be prescribed by veterinarians as a non-approved drug. Production systems, weaning feed and hygienic levels on the farms have been improved since 1986 and theuse of in-feed medications has been reduced during the late 90s (1). The national efficiency control still show somewhat higher post-weaning mortality (0.5%) and 1-2 days older 25 kg pigs compared to before 1986. However there are farms having better production results today compared to before -86 (5). As practitioners we find that PWD problems are often seen in some particular herds but not in others. This has led to the question on what is happening during the weaning period, how are the newly weaned pigs taken care of, and what are the problems?