Introduction.

The Swedish control programme for paratuberculosis is based on faecal culture. With this method, mould overgrowth is sometimes a problem, especially if affecting a large number of samples from a herd. This was the case with two beef herds in the programme. The mould identified in most of the samples was Pseudallescheria boydii (anamorph state, Scedosporium apiospermum).

Methods and materials.

When the problem with mould overgrowth remained after repeated sampling in the two herds, further investigations were undertaken. Samples from feed and straw were examined for the presence of mould. The farmers were interviewed about feed quality, animal health etc. An intensive programme for faecal sampling was suggested. This was not deemed practical and, instead, faecal samples were taken on 3 occasions in each herd.

Results.

Samples taken from feed in herd A showed low numbers of mould in both silage and straw while herd B had moderate numbers of mould in the straw and high numbers in the silage. None of the feed samples yielded growth of P. boydii. In herd A 53% of the faecal samples taken at the same time as the feed samples were overgrown by mould and another 20% yielded some mould growth. In most cases the mould was P. boydii. From herd B, 43% of the faecal samples were overgrown by mould, while another 18% yielded some mould growth. In this herd most cases of overgrowth was due to P. boydii, but a number of samples also yielded growth of other mould species.

Discussion.

For practical reasons, most large beef farms are sampled during the cold season, when the animals are indoors and easier to catch and handle. However, the risk of mould overgrowth may be higher during this period. Faecal samples from animals on pasture are thought less likely to be overgrown by mould. This study could, however, not substantiate that theory.